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we observed the field of grb 190613b (fermi trigger 582115625.049376/190613449; gcn #24806, swift trigger 908329; d'ai et al., gcn #24807) simultaneously in g'r'i'z'jhk with grond (greiner et al. 2008, pasp 120, 405) mounted at the 2.2 m mpg telescope at eso la silla observatory (chile). observations started at 09:18 ut on 14 june 2019, 22.4 hrs after the grb trigger. they were performed at an average seeing of 1.4" and at an average airmass of 1.2. we detect a single point source in our g'r'i'z'jh images consistent with the reported grb optical and x-ray afterglow (beardmore et al., gcn #24812, marshall et al., gcn #24817). based on a total 22 min exposure in g'r'i'z' and 22 min in jhk, we estimate the following preliminary magnitudes (all in vega system): g' = 22.79 +/- 0.05 mag r' = 22.05 +/- 0.04 mag i' = 21.56 +/- 0.05 mag z' = 21.15 +/- 0.07 mag j = 20.5 +/- 0.1 mag h = 20.2 +/- 0.2 mag k > 19.8 mag given magnitudes are calibrated against panstarrs as well as 2mass field stars and are not corrected for the expected galactic foreground extinction corresponding to a reddening of e_(b-v)=0.06 mag in the direction of the burst (schlafly & finkbeiner 2011). we thank the observer astronomer at the mpg 2.2m in la silla for their help in obtaining these data. | grb 190613b: grond detection of the optical/nir afterglow |
at 00:28:33 ut, the swift burst alert telescope (bat) triggered and located a short grb 210919a (trigger=1073893). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 80.230, +1.274 which is ra(j2000) = 05h 20m 55s dec(j2000) = +01d 16' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single-peaked structure with a duration of about 0.3 sec. the peak count rate was ~3500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 00:30:10.5 ut, 97.0 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 80.25441, 1.31189 which is equivalent to: ra(j2000) = 05h 21m 01.06s dec(j2000) = +01d 18' 42.8" with an uncertainty of 6.9 arcseconds (radius, 90% containment). this location is 162 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.56 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 99 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.142. burst advocate for this burst is a. tohuvavohu (tohuvavohu at astro.utoronto.ca). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 210919a: swift detection of a short burst |
at 13:29:37 ut, the swift burst alert telescope (bat) triggered and located grb 191220a (trigger=945344). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 281.391, +26.667 which is ra(j2000) = 18h 45m 34s dec(j2000) = +26d 40' 02" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 20 sec. the peak count rate was ~200 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 13:31:50.2 ut, 132.4 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 281.37924, 26.65599 which is equivalent to: ra(j2000) = 18h 45m 31.02s dec(j2000) = +26d 39' 21.6" with an uncertainty of 3.8 arcseconds (radius, 90% containment). this location is 54 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.53 x 10^21 cm^-2 (willingale et al. 2013). the initial flux in the 2.5 s image was 4.03e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 250 seconds with the u filter starting 137 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.2 mag. the 8'x8' region for the list of sources generated on-board covers 0.00% of the xrt error circle. no correction has been made for the expected extinction corresponding to e(b-v) of 0.14. burst advocate for this burst is s laha (sib.laha at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 191220a: swift detection of a burst |
swift-xrt has performed follow-up observations of the fermi-gbm and swift/bat-detected burst grb 201216a (gbm team, gcn circ. 29057; tohuvavohu et al. gcn circ. 29059), collecting 4.9 ks of photon counting (pc) mode data between t0+21.5 ks and t0+34.2 ks. no x-ray sources have been detected consistent with being within 197 arcsec of the swift/bat position. the 3-sigma upper limit in the field ranges from ~0.002 to ~0.003 ct s^-1, corresponding to a 0.3-10 kev observed flux of 7.3e-14 to 1.1e-13 erg cm^-2 s^-1 (assuming a typical grb spectrum). seven uncatalogued sources were detected too far from the grb position to be likely afterglow candidates. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021408. this circular is an official product of the swift-xrt team. | grb 201216a: swift-xrt observations |
at 18:01:51 ut, the swift burst alert telescope (bat) triggered and located grb 220611a (trigger=1110090). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 66.526d, -37.289d which is ra(j2000) = 04h 26m 06s dec(j2000) = -37d 17' 20 with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). due to a telemetry gap, the bat onboard lightcurve is not immediately available. however, the triggering algorithm found the source in an 8 second image, indicating a long grb. the xrt began observing the field at 18:04:20.4 ut, 149.2 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 66.51418, -37.25899 which is equivalent to: ra(j2000) = 04h 26m 03.40s dec(j2000) = -37d 15' 32.4" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 113 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 2.66 x 10^20 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 152 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.033. we note that this source location is ~15 arcsec from the line of sight to the galaxy mcg-06-10-007, which is described in simbad as an s0 galaxy, b=16.3, z~0.049, angular size 18"x16". burst advocate for this burst is s. b. cenko (brad.cenko at nasa.gov). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 220611a: swift detection of a burst |
at 10:19:01 ut, the swift burst alert telescope (bat) triggered and located grb 230420a (trigger=1164980). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 161.013, +32.087 which is ra(j2000) = 10h 44m 03s dec(j2000) = +32d 05' 11" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 30 sec. the peak count rate was ~800 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 10:20:32.9 ut, 91.8 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source with an enhanced position: ra, dec 161.04899, 32.10766 which is equivalent to: ra(j2000) = 10h 44m 11.76s dec(j2000) = +32d 06' 27.6" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 132 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.71 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 2.1 (+2.19/-1.93) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 3.05e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 99 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.017. burst advocate for this burst is n. j. klingler (noelklin at umbc.edu). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 230420a: swift detection of a burst |
at 13:32:56 ut, the swift burst alert telescope (bat) triggered and located grb 191122a (trigger=938899). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 54.296, -32.176 which is ra(j2000) = 03h 37m 11s dec(j2000) = -32d 10' 32" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single-peaked structure with a duration of about 50 sec. the peak count rate was ~1200 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 13:34:31.1 ut, 94.7 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 54.26926, -32.18602 which is equivalent to: ra(j2000) = 03h 37m 04.62s dec(j2000) = -32d 11' 09.7" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 89 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. no spectrum from the promptly downlinked event data is yet available to determine the column density. the initial flux in the 2.5 s image was 1.89e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 103 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.01. burst advocate for this burst is b. sbarufatti (bxs60 at psu.edu). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 191122a: swift detection of a burst |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 220310c, collecting 4.6 ks of photon counting (pc) mode data between t0+102.8 ks and t0+120.2 ks. four uncatalogued x-ray sources have been detected, however none of them is above the rass limit or shows definitive signs of fading. therefore, at the present time we cannot identify which, if any, is the afterglow. details of these sources are given below: source 1: ra (j2000.0): 289.9580 = 19:19:49.91 dec (j2000.0): +40.2093 = +40:12:33.3 error: 7.9 arcsec (radius, 90% conf. [enhanced position]) count-rate: (4.4 +/- 1.2)e-3 ct s^-1 distance: 344 arcsec from swift/bat-guano position. flux: (9.6 +/- 2.7)e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 290.2354 = 19:20:56.50 dec (j2000.0): +40.3333 = +40:19:59.9 error: 7.6 arcsec (radius, 90% conf.) count-rate: (3.7 [+1.4, -1.1])e-3 ct s^-1 distance: 539 arcsec from swift/bat-guano position. flux: (1.39 [+0.51, -0.42])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 3: ra (j2000.0): 290.1544 = 19:20:37.05 dec (j2000.0): +40.2064 = +40:12:23.0 error: 6.3 arcsec (radius, 90% conf.) count-rate: (1.92 [+0.98, -0.76])e-3 ct s^-1 distance: 288 arcsec from swift/bat-guano position. flux: (4.2 [+2.2, -1.7])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 4: ra (j2000.0): 289.8727 = 19:19:29.46 dec (j2000.0): +40.2572 = +40:15:26.0 error: 6.4 arcsec (radius, 90% conf.) count-rate: (1.41 [+0.96, -0.69])e-3 ct s^-1 distance: 540 arcsec from swift/bat-guano position. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021483. this circular is an official product of the swift-xrt team. | grb 220310c: swift-xrt observations |
long-duration gamma-ray bursts provide a unique way of selecting a sample of actively star-forming galaxies independent of their brightness and at practically any redshift. i will review what we know about the hosts and more immediate environments of grbs from two different perspectives: ultraviolet absorption-line spectroscopy of the bright early afterglow, and spectroscopy and multi-wavelength photometry of the hosts in emission once the afterglow has faded away. | the host galaxies of long-duration gamma-ray bursts in absorption and in emission |
at 04:35:56 ut, the swift burst alert telescope (bat) triggered and located grb 191011a (trigger=928924). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 44.724, -27.845 which is ra(j2000) = 02h 58m 54s dec(j2000) = -27d 50' 40" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex peak structure with a duration of about 20 sec. the peak count rate was ~3000 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 04:37:11.1 ut, 74.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 44.72679, -27.84594 which is equivalent to: ra(j2000) = 02h 58m 54.43s dec(j2000) = -27d 50' 45.4" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 9.5 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.54 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 5.8 (+3.35/-2.89) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 77 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 02:58:54.80 = 44.72832 dec(j2000) = -27:50:43.5 = -27.84541 with a 90%-confidence error radius of about 0.83 arc sec. this position is 6.1 arc sec. from the center of the xrt error circle. the estimated magnitude is 20.20 with a 1-sigma error of about 0.19. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. burst advocate for this burst is s. l laha (sib.laha at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 191011a: swift detection of a burst with an optical counterpart |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 220617a (di lalla et al. gcn circ. 32212), collecting 4.9 ks of photon counting (pc) mode data between t0+23.9 ks and t0+37.1 ks. five uncatalogued x-ray sources have been detected, however none of them is above the rass limit or shows definitive signs of fading. therefore, at the present time we cannot identify which, if any, is the afterglow. details of these sources are given below. please note: due to an error, the original gcn announcing these swift observations (gcn 32211) referred to "grb 220617b", whereas the observations were of grb 220617a. source 1: ra (j2000.0): 157.1531 = 10:28:36.74 dec (j2000.0): +15.4493 = +15:26:57.6 error: 6.4 arcsec (radius, 90% conf.) count-rate: (2.7 [+1.5, -1.1])e-3 ct s^-1 distance: 730 arcsec from fermi/lat position. flux: (5.5 [+3.0, -2.2])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 156.9298 = 10:27:43.15 dec (j2000.0): +15.4059 = +15:24:21.1 error: 6.4 arcsec (radius, 90% conf.) count-rate: (1.45 [+0.92, -0.65])e-3 ct s^-1 distance: 458 arcsec from fermi/lat position. source 3: ra (j2000.0): 157.0400 = 10:28:9.60 dec (j2000.0): +15.4886 = +15:29:19.1 error: 6.4 arcsec (radius, 90% conf.) count-rate: (1.67 [+0.91, -0.69])e-3 ct s^-1 distance: 314 arcsec from fermi/lat position. source 4: ra (j2000.0): 156.9896 = 10:27:57.50 dec (j2000.0): +15.4454 = +15:26:43.4 error: 5.7 arcsec (radius, 90% conf.) count-rate: (1.75 [+0.93, -0.70])e-3 ct s^-1 distance: 321 arcsec from fermi/lat position. source 5: ra (j2000.0): 156.8566 = 10:27:25.60 dec (j2000.0): +15.3577 = +15:21:27.8 error: 6.3 arcsec (radius, 90% conf.) count-rate: 0.0114 [+0.0046, -0.0036] ct s^-1 distance: 716 arcsec from fermi/lat position. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021505. this circular is an official product of the swift-xrt team. | grb 220617a: swift-xrt observations |
"at 09:08:40.71 ut on 12 april 2020, the fermi gamma-ray burst monitor (gbm) triggered and located grb 200412b (trigger 608375325 / 200412381), which was also detected by the fermi lat (longo et al. 2020, gcn 27557) and observed to have a candidate optical afterglow by master (gcn 27555 & gcn 27556). the gbm on-ground location is consistent with the lat position. the angle from the fermi lat boresight at the gbm trigger time is 59 degrees. the gbm light curve shows a multi-peaked structure with a duration (t90) of about 6 s (50-300 kev). the time-averaged spectrum from t0+3.1s to t0+21.5 s is best fit by a band function with epeak = 257 +/- 4 kev, alpha = -0.54 +/- 0.01, and beta = -2.24 +/- 0.02. the event fluence (10-1000 kev) in this time interval is (8.00 +/- 0.04)e-05 erg/cm^2. the 1-sec peak photon flux measured starting from t0+9.1 s in the 10-1000 kev band is 127.5 +/- 0.7 ph/s/cm^2. the spectral analysis results presented above are preliminary; final results will be published in the gbm grb catalog: https://heasarc.gsfc.nasa.gov/w3browse/fermi/fermigbrst.html for fermi gbm data and info, please visit the official fermi gbm support page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" | grb 200412b: fermi gbm detection |
at 03:46:30 ut, the swift burst alert telescope (bat) triggered and located grb 201013a (trigger=999948). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 107.388, +57.036 which is ra(j2000) = 07h 09m 33s dec(j2000) = +57d 02' 09" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a double-peaked structure with a duration of about 15 sec. the peak count rate was ~29000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 03:47:39.9 ut, 69.3 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 107.3945, 57.0347 which is equivalent to: ra(j2000) = 07h 09m 34.69s dec(j2000) = +57d 02' 05.0" with an uncertainty of 2.4 arcseconds (radius, 90% containment). this location is 13 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data does not constrain the column density. uvot took a finding chart exposure of 150 seconds with the white filter starting 73 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.05. burst advocate for this burst is k. l. page (klp5 at leicester.ac.uk). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 201013a: swift detection of a burst |
several thousand gamma-ray bursts (grbs) have now been detected, lasting from a fraction of a second to several hours, and with spectral energies peaking in the hundreds of kev range. a handful of bursts have been detected at gev energies, but very recently grb 190114c became the first grb to be identified in the tev regime via the detection of a flash of chernkov light by the magic telescope. this detection offers a new window on the grb phenomena, probing the generation of these extreme photons, as well as a route to testing the scattering of such photons off the extragalactic background light (ebl). the environment of the burst is also exceptional, being extremely dense and perhaps indicating a link between the very high energy emisison and environment, as suggested by some models. our proposed hst observaitons will track the late time behaviour of the counterpart, disentangle the supernova, afterglow and host emission and determine if the physics of this unique burst differs from that seen in other examples. the observations will also characterise the environment in emission, dissecting it at higher resolution than possible from the ground and tying the emission to absorption properties. finally, the observations will measure the optical photon density close to the grb itself (i.e. in the host), and hence the contribution of these photons to the scattering of very high energy light (i.e. the total of local to the burst + ebl). this in turn will enable the determination of the true energetics of the burst at tev energies and test scattering models in the ebl, both key questions in high energy astrophysics and cosmology. | unpicking the exceptional properties of the first tev emitting gamma-ray burst |
at 21:04:43 ut, the swift burst alert telescope (bat) triggered and located grb 230116d (trigger=1149293). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 98.594, 49.840d which is ra(j2000) = 06h 34m 23s dec(j2000) = +49d 50' 24" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). due to a communications gap the bat lightcurve before t+8 s is not immediately available, but the later lightcurve indicates activity out to at least t+30 s. the xrt began observing the field at 21:06:54.1 ut, 130.9 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 98.61709, 49.87257 which is equivalent to: ra(j2000) = 06h 34m 28.10s dec(j2000) = +49d 52' 21.3" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 128 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.65 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 133 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.112. burst advocate for this burst is e. sonbas (edasonbas at yahoo.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 230116d: swift detection of a burst |
at 22:02:09 ut, the swift burst alert telescope (bat) triggered and located grb 170531b (trigger=755354). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 286.895, -16.426 which is ra(j2000) = 19h 07m 35s dec(j2000) = -16d 25' 34" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of at least 50 sec. the peak count rate was ~2000 counts/sec (15-350 kev), at ~6 sec after the trigger. the xrt began observing the field at 22:04:30.1 ut, 140.9 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source with an enhanced position: ra, dec 286.8835, -16.4196 which is equivalent to: ra(j2000) = 19h 07m 32.03s dec(j2000) = -16d 25' 10.4" with an uncertainty of 2.3 arcseconds (radius, 90% containment). this location is 45 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.41 x 10^21 cm^-2 (willingale et al. 2013). the initial flux in the 2.5 s image was 2.73e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 152 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. no correction has been made for the expected extinction corresponding to e(b-v) of 0.19. burst advocate for this burst is p.a. evans (pae9 at star.le.ac.uk). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/too.html.) | grb 170531b: swift detection of a burst |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 210413b (swift/bat did not successfully trigger on grb 210413b et al. gcn circ. 29819), collecting 4.9 ks of photon counting (pc) mode data between t0+185.0 ks and t0+206.7 ks. one uncatalogued x-ray source has been detected consistent with being within 394 arcsec of the swift/bat position, it is below the rass limit and shows no definitive signs of fading. therefore, at the present time we cannot confirm this as the afterglow. details of this source are given below: source 1: ra (j2000.0): 182.5333 = 12:10:7.98 dec (j2000.0): +56.0497 = +56:02:59.0 error: 5.7 arcsec (radius, 90% conf. [enhanced position]) count-rate: (4.5 +/- 1.2)e-3 ct s^-1 distance: 309 arcsec from swift/bat position. flux: (1.42 +/- 0.39)e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) three uncatalogued sources were also detected too far from the grb position to be likely afterglow candidates. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021428. this circular is an official product of the swift-xrt team. | grb 210413b: swift-xrt observations |
at 05:28:01 ut, the swift burst alert telescope (bat) triggered and located grb 210517a (trigger=1048783). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 358.174, -39.105 which is ra(j2000) = 23h 52m 42s dec(j2000) = -39d 06' 17" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat lightcurve shows a peak at least 2 seconds long and a maximum count rate of ~2200 counts/s (15-350 kev). the xrt began observing the field at 05:29:08.6 ut, 67.0 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 358.2245, -39.1020 which is equivalent to: ra(j2000) = 23h 52m 53.88s dec(j2000) = -39d 06' 07.2" with an uncertainty of 2.1 arcseconds (radius, 90% containment). this location is 141 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.30 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 5.2 (+2.58/-2.26) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 69 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.011. burst advocate for this burst is v. d'elia (valerio.delia at ssdc.asi.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 210517a: swift detection of a burst |
at 20:48:40 ut, the swift burst alert telescope (bat) triggered and located grb 211221a (trigger=1090472). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 78.938, +0.940 which is ra(j2000) = 05h 15m 45s dec(j2000) = +00d 56' 25" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex peak structure with a duration of about 20 sec. the peak count rate was ~1700 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 20:49:34.9 ut, 54.1 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 78.89820, 0.91421 which is equivalent to: ra(j2000) = 05h 15m 35.57s dec(j2000) = +00d 54' 51.2" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 170 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.37 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 9 (+4.75/-2.44) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 6.82e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 63 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.143. burst advocate for this burst is k. l. page (kimlpage1978 at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 211221a: swift detection of a burst |
at 01:41:00 ut, the swift burst alert telescope (bat) triggered and located grb 200122a (trigger=950330). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 209.981, +27.566 which is ra(j2000) = 13h 59m 55s dec(j2000) = +27d 33' 56" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 50 sec. the peak count rate was ~11000 counts/sec (15-350 kev), at ~10 sec after the trigger. the xrt began observing the field at 01:42:12.5 ut, 72.2 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 210.01625, 27.54988 which is equivalent to: ra(j2000) = 14h 00m 03.90s dec(j2000) = +27d 32' 59.6" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 126 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.54 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 1 (+0.55/-0.45) x 10^22 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 9.13e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 81 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.03. burst advocate for this burst is e. sonbas (edasonbas at yahoo.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200122a: swift detection of a burst |
at 05:44:52 ut, the swift burst alert telescope (bat) triggered and located grb 201209a (trigger=1011980). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 23.106, -1.763 which is ra(j2000) = 01h 32m 25s dec(j2000) = -01d 45' 47" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a double-peaked structure with a duration of about 30 sec. the peak count rate was ~8000 counts/sec (15-350 kev), at ~7 sec after the trigger. the xrt began observing the field at 05:46:44.1 ut, 111.7 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 23.09079, -1.75347 which is equivalent to: ra(j2000) = 01h 32m 21.79s dec(j2000) = -01d 45' 12.5" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 64 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 3.60 x 10^20 cm^-2 (willingale et al. 2013). the initial flux in the 2.5 s image was 6.48e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 121 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.04. burst advocate for this burst is j.d. gropp (jdg44 at psu.edu). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 201209a: swift detection of a burst |
ixpe performed the first observation of x-ray polarization of a grb afterglow in the 2-8 kev energy range. ixpe observed grb 221009a from 2022-10-11t23:34:28utc to 2022-10-14t00:45:31utc for an effective exposure of 100 ks. from a quick-look analysis of the image-, time- and energy- averaged low-level instrument data (prior to pipeline processing at the ixpe soc), we report: polarization degree (pd) upper limits are derived with 99% c.l. these results are preliminary. | grb 221009a: ixpe preliminary upper limits of x-ray polarization |
at 13:32:33 ut, the swift burst alert telescope (bat) triggered and located grb 200216b (trigger=956824). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 160.461, +19.454 which is ra(j2000) = 10h 41m 51s dec(j2000) = +19d 27' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed one long peak with a duration of about 30 sec, there is possible evidence for weaker emission out to t0+60 seconds. the peak count rate was ~2000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 13:34:29.0 ut, 115.1 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source with an enhanced position: ra, dec 160.4343, 19.4757 which is equivalent to: ra(j2000) = 10h 41m 44.23s dec(j2000) = +19d 28' 32.4" with an uncertainty of 2.0 arcseconds (radius, 90% containment). this location is 119 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (2.03 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 9.9 (+3.22/-2.80) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 1.33e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 124 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. burst advocate for this burst is p. d'avanzo (paolo.davanzo at inaf.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200216b: swift detection of a burst |
swift-xrt has performed a second follow-up observation of the integral/spi-acs and swift-bat guano detected possible short burst grb 200405b (james delaunay et al. gcn circ. 27497), collecting ~1.2 ks of photon counting (pc) mode data between t0+550.8 ks and t0+584.0 ks. of the four uncatalogued x-ray sources reported in gcn 27500 (sbarufatti et al.), none shows any evidence of fading. we therefore conclude that swift did not detect the x-ray afterglow of this grb. this circular is an official product of the swift-xrt team. | grb 200405b: further swift-xrt observations |
at 18:15:37 ut, the swift burst alert telescope (bat) triggered and located grb 220306b (trigger=1095288). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 5.378, +71.354 which is ra(j2000) = 00h 21m 31s dec(j2000) = +71d 21' 14" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 15 sec. the peak count rate was ~2600 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 18:17:03.3 ut, 85.9 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 5.38628, 71.36313 which is equivalent to: ra(j2000) = 00h 21m 32.71s dec(j2000) = +71d 21' 47.3" with an uncertainty of 4.0 arcseconds (radius, 90% containment). this location is 34 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 4.07 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 89 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.578. burst advocate for this burst is r. caputo (regina.caputo at nasa.gov). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 220306b: swift detection of a burst |
at 11:21:20 ut, the swift burst alert telescope (bat) triggered and located grb 221216a (trigger=1144698). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 326.021, -34.405 which is ra(j2000) = 21h 44m 05s dec(j2000) = -34d 24' 17" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of at least 200 sec. the peak count rate was ~1640 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 11:22:32.6 ut, 71.7 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 326.0326, -34.4223 which is equivalent to: ra(j2000) = 21h 44m 7.82s dec(j2000) = -34d 25' 20.3" with an uncertainty of 4.8 arcseconds (radius, 90% containment). no event data are yet available to determine the column density using x-ray spectroscopy. uvot took a finding chart exposure of 150 seconds with the white filter starting 81 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.042. burst advocate for this burst is s. dichiara (simonedichiara55 at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 221216a: swift detection of a burst |
gamma-ray bursts (grbs) are the brightest transients in the mev sky, and their association with gravitational wave producing binary neutron star mergers is a topic at the forefront of multi-messenger astrophysics. grbs have been studied for decades with wide-field-of-view background-dominated monitoring instruments, but with a sensitive mev instrument like amego, there is great potential for understanding the fainter populations of nearby short duration grbs within the gravitational wave detector horizons, including those that may be slightly off-axis like grb 170817a associated with gw170817. initial estimates suggest that amego will be the most prolific detector of grbs to have ever flown, and will also be sensitive to a significant number of long duration grbs at high redshifts (z > 5). sensitive mev observations of grb spectral and temporal evolution as well as potentially polarization of bright events, will provide insight into grb prompt emission mechanisms, as well as probe synchrotron shocks physics by measuring mev grb afterglows of bright bursts. | gamma-ray bursts and gravitational wave counterparts with amego |
"we initiated observations with the chandra x-ray observatory of the position of the short-duration grb 200411a (fermi-gbm et al., gcn 27535; tohuvavohu et al., gcn 27536; bissaldi et al., gcn 27543) starting on 2020 april 15 00:16:54 ut, or at a mid-time of 3.95 days after the grb trigger. acis-s observations were taken under proposal 21500089 (obsid 22427; pi: berger), with a total exposure time of 19.8 ksec. we do not detect an x-ray source within or around the enhanced swift-xrt position (90% confidence; osborne et al., gcn 27538). centered on the xrt position, we calculate a 3-sigma limit of <4.5e-4 cts/s in the 0.5-8 kev energy range following the method described by gehrels (1986) for small numbers of events. applying the best-fit pc mode xrt spectral parameters (gamma=1.7, intrinsic nh=1.5e21 cm^-2) and fixing the galactic nh=1.55e20 cm^-2 (willingale et al. 2013), we calculate a 3-sigma unabsorbed flux limit of fx<8.4e-15 erg/s/cm^2 in the 0.3-10 kev energy range. the xrt afterglow starting from 200 sec post-burst exhibits a power-law decline with decay index alpha=-0.84 (+/- 0.2) (where fx~t^alpha), while the chandra upper limit indicates a potential steepening to alpha<-1.3. if this steepening is interpreted as a jet break at ~0.5-2 days post-burst, using median values for the explosion properties and redshift based on properties of short grbs gives an opening angle of ~4-7 degrees. we thank the chandra staff for the rapid planning and scheduling of these observations." | grb 200411a: chandra observations indicative of temporal steepening |
"we initiated observations with the chandra x-ray observatory of the short-duration grb 201006a (barthelmy et al., gcn 28560; tohuvavohu, gcn 28563; hamburg et al., gcn 28564; lien et al., gcn 28567) starting on 2020 october 09 20:57:42 ut, with a median observation time of 3.98 days post-trigger. we obtained one acis-s observation under the proposal 21400447 (obsid 22401; pi: fong), with an effective exposure time of 24.7 ks. we do not detect an x-ray source within the enhanced swift-xrt position (90% confidence; evans et al., gcn 28562). centered on the xrt position, we obtain a 3-sigma limit of <3.6e-4 cts/s in the 0.5-8 kev energy range (following gehrels 1986). applying the best-fit pc-mode xrt spectral parameters (gamma=2.1, total nh=1.3e22 cm^-2; evans et al., gcn 28568), we calculate a 3-sigma unabsorbed flux limit of fx<1.15e-14 erg/s/cm^2 in the 0.3-10 kev energy range. the xrt afterglow, starting at ~153.3 s post-burst, can be modeled with a power law decline (where fx~t^alpha) with a decay index of alpha=-0.99(+0.14,-0.13) consistent with the results of evans et al. (gcn 28568). our chandra upper limit is marginally consistent with the expected flux at dt~3.98 days drawn by this model. we thank the chandra director, patrick slane, and staff for the rapid planning and scheduling of these observations." | grb 201006a: chandra upper limit on the x-ray afterglow |
gamma-ray bursts are bright enough to be seen to very great distances and their afterglows can provide redshifts and positions for their host galaxies, and in some cases details of the ism and the igm close to the burst, irrespective of the host magnitude itself. thus grbs, despite their small numbers, offer a unique and powerful tracer of early star formation and the galaxy populations in the era of reionization. our efforts to identify high-z grbs have been rewarded with the discoveries of grb 090423 and grb 120923a at spectroscopic redshifts of 8.2 and 7.8 respectively. however, it remains the case that some good candidate high-z grbs cannot be followed up quickly or deeply enough with ground-based ir spectroscopy, and indeed for others the ly-alpha break may fall in regions of the ir spectrum difficult to access from the ground. grb 090429b is an example, which had a photo-z of 9.4, but for which spectroscopy was curtailed due to bad weather. wfc3/ir on hst can obtain redshifts based on the location of the ly-alpha break via slitless grism spectroscopy to considerably deeper limits (and hence later times) than is possible from the ground, thus offering a solution to this problem. this proposal aims to continue to build the sample of z>7 grbs by obtaining spectroscopy for up to two candidates for which photometry suggests a very high redshift, but where the redshift could not be secured from the ground. this will provide an important legacy of host galaxy targets with known redshifts for future studies with jwst. the low rate of z>7 grbs leads us to request a long-term too program, spanning cycles 25 and 26. | identifying gamma-ray bursts at very high redshifts |
binary stellar systems that involve a neutron star or two neutron stars make interesting phenomena, x-ray bursts and kilo-novae, respectively, which involve explosive burning either in the proton-rich environment or in the neutron-rich environment. these are very important problems for nuclear astrophysics. first, the current effort for the explosive hydrogen burning, the rapid proton capture (rp) process which would take place on a neutron star surface in x-ray burst is discussed together with a new x-ray observation that suggests the rp-process termination at around a = 100. the observation of the afterglow of the binary neutron star merger appears to be the kilo-nova predicted in the last decade in nuclear astrophysics, and to be the great success of the field. however, the detailed study of the kilo-nova by the r-process should be a great challenge for full understanding heavy element synthesis and the neutron star merger. nuclear physics problems are discussed for the kilonova. | experimental challenge to heavy element synthesis under explosive burning on neutron stars |
at 02:34:57 ut, the swift burst alert telescope (bat) triggered and located grb 200303a (trigger=959431). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 212.698, +51.360, which is ra(j2000) = 14h 10m 47s dec(j2000) = +51d 21' 35" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows a multi-peak structure with a duration of about 60 sec. the peak count rate was ~3500 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 02:36:25.1 ut, 87.7 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 212.7173, 51.3583 which is equivalent to: ra(j2000) = 14h 10m 52.15s dec(j2000) = +51d 21' 29.9" with an uncertainty of 4.7 arcseconds (radius, 90% containment). this location is 43 arcseconds from the bat onboard position, within the bat error circle. no event data are yet available to determine the column density using x-ray spectroscopy. the initial flux in the 2.5 s image was 8.77e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 96 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. this source lies within the current (sector 22) field-of-view of tess camera 3. burst advocate for this burst is s. b. cenko (brad.cenko at nasa.gov). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200303a: swift detection of a burst |
at 01:49:34 ut, the swift burst alert telescope (bat) triggered and located grb 200630a (trigger=980210). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 91.380, -60.789 which is ra(j2000) = 06h 05m 31s dec(j2000) = -60d 47' 20" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 10 sec. the peak count rate was ~1600 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 01:50:52.3 ut, 77.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 91.3308, -60.7524 which is equivalent to: ra(j2000) = 06h 05m 19.38s dec(j2000) = -60d 45' 08.6" with an uncertainty of 2.6 arcseconds (radius, 90% containment). this location is 157 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 4.33 x 10^20 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 82 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.04. this burst is consistent with fermi/gbm trigger number 615174580. burst advocate for this burst is k. l. page (klp5 at leicester.ac.uk). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200630a: swift detection of a burst |
at 13:11:04 ut, the swift burst alert telescope (bat) triggered and located grb 200906a (trigger=994856). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 272.293, +67.852 which is ra(j2000) = 18h 09m 10s dec(j2000) = +67d 51' 08" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed two main peaks with a duration of about 80 sec. the second, larger, peak extends past the end of the slew and into the interval observed by xrt and uvot. the peak count rate was ~3000 counts/sec (15-350 kev), at ~52 sec after the trigger. the xrt began observing the field at 13:12:10.8 ut, 66.7 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source with an enhanced position: ra, dec 272.2731, 67.8791 which is equivalent to: ra(j2000) = 18h 09m 05.54s dec(j2000) = +67d 52' 44.8" with an uncertainty of 2.6 arcseconds (radius, 90% containment). this location is 101 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (5.25 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 5.5 (+6.91/-5.25) x 10^21 cm^-2 (90% confidence). the initial flux in the 0.1 s image was 2.09e-08 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 76 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.05. burst advocate for this burst is k. l. page (klp5 at leicester.ac.uk). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200906a: swift detection of a burst |
at 18:51:11 ut, the swift burst alert telescope (bat) triggered and located grb 200907b (trigger=995004). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 89.013, +6.911 which is ra(j2000) = 05h 56m 03s dec(j2000) = +06d 54' 38" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 1 sec. the peak count rate was ~4000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 18:52:31.3 ut, 80.1 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 89.02837, 6.90752 which is equivalent to: ra(j2000) = 05h 56m 06.81s dec(j2000) = +06d 54' 27.1" with an uncertainty of 3.8 arcseconds (radius, 90% containment). this location is 56 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 4.23 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 83 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.61. burst advocate for this burst is a. p. beardmore (apb at star.le.ac.uk). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200907b: swift detection of a short burst |
we examined the latest, enhanced xrt position of the long grb 200729a detected by swift (evans et al., gcn 28165) in pan-starrs imaging. we downloaded the pan-starrs dr1 images and note the presence of a faint source detected within the xrt error circle (90% confidence osborne et al., gcn 28168) at: ra (j2000) = 12:17:30.32 dec (j2000) = +45:35:41.4 the location of this source is consistent with the pre-burst counterpart detected in spitzer/irac imaging (laskar et al., gcn 28171). using a 1.5 arcsec aperture, we measure that the source has i=21.4+/-0.2 mag, y=21.0+/-0.2 mag, and z=21.0+/-0.1 mag. we note that our z-band photometry is 1 magnitude brighter than the limit reported by not (malesani et al., gcn 28169). the source is not obviously detected in either pan-starrs g or r-band imaging. the source may be marginally extended, although it is too faint to definitively determine whether the source is intrinsically extended beyond the psf of the pan-starrs dr1 imaging. based on the column of neutral hydrogen inferred from the swift/xrt x-ray spectrum (7.1e21 cm-2; https://www.swift.ac.uk/xrt_unenh_positions/00984929/), the total optical extinction to any counterpart is approximately a_v = 3.7 mag (guver & ozel, 2009, mnras, 400, 2050). assuming the pan-starrs source is in ngc 4242 with a trgb distance of 5.3 mpc (sabbi et al. 2018, apjs, 235, 23), any stellar counterpart would have m_i~-9.3 mag, which is extremely luminous for a star even with initial mass > 25 m_sun. thus the lack of an optical or near-infrared counterpart (hu et al., gcn 28167; lipunov et al., gcn 28166; malesani et al., gcn 28169; d'avanzo et al., gcn 28170) and large implied luminosity suggests that a supernova or non-terminal outburst from such a star in ngc 4242 is unlikely. alternatively, if the source is a background galaxy, and the i-z color represents a 4000 angstrom break, this places the redshift of the galaxy at z~1.1, which would provide a natural explanation for the faint xrt flux (gcn 28165), and the lack of detected optical or nir afterglow. | grb 200729a: pan-starrs pre-explosion source detection |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 200219c (dirirsa et al. gcn circ. 27151) in a series of observations tiled on the sky. the total exposure time is 2.4 ks, distributed over 4 tiles; the maximum exposure at a single sky location was 2.4 ks. the data were collected between t0+43.0 ks and t0+56.0 ks, and are entirely in photon counting (pc) mode. two uncatalogued x-ray sources are detected, of which one ("source 2") is above the rass limit, and is therefore likely the grb afterglow. using 2417 s of pc mode data and 5 uvot images, we find an enhanced xrt position (using the xrt-uvot alignment and matching uvot field sources to the usno-b1 catalogue): ra, dec = 262.50899, +10.53933 which is equivalent to: ra (j2000): 17h 30m 02.16s dec(j2000): +10d 32' 21.6" with an uncertainty of 2.1 arcsec (radius, 90% confidence). this position is 12.9 arcmin from the fermi/lat position. the light curve is consistent with a constant source of mean count rate 1.1e-01 ct/sec. a power-law fit gives an index of 0.9 (+1.4, -1.5). a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 2.1 (+/-0.4). the best-fitting absorption column is 3.2 (+1.6, -1.4) x 10^21 cm^-2, in excess of the galactic value of 1.2 x 10^21 cm^-2 (willingale et al. 2013). the counts to observed (unabsorbed) 0.3-10 kev flux conversion factor deduced from this spectrum is 3.1 x 10^-11 (4.9 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 3.2 (+1.6, -1.4) x 10^21 cm^-2 galactic foreground: 1.2 x 10^21 cm^-2 excess significance: 2.4 sigma photon index: 2.1 (+/-0.4) the results of the xrt-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020973. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00088. this circular is an official product of the swift-xrt team. | grb 200219c: swift-xrt afterglow detection |
at 00:27:30 ut, the swift burst alert telescope (bat) triggered and located grb 210421a (trigger=1044426). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 104.908, +4.934, which is ra(j2000) = 06h 59m 38s dec(j2000) = +04d 56' 03" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 40 sec. the peak count rate was ~1500 counts/sec (15-350 kev), at ~2 sec after the trigger. the xrt began observing the field at 00:28:58.1 ut, 87.8 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 104.87569, 4.92168 which is equivalent to: ra(j2000) = 06h 59m 30.17s dec(j2000) = +04d 55' 18.0" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 124 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. no spectrum from the promptly downlinked event data is yet available to determine the column density. the initial flux in the 0.1 s image was 1.51e-08 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 96 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the large, but uncertain, extinction expected. burst advocate for this burst is m. j. moss (mikejmoss3 at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 210421a: swift detection of a burst |
at 04:10:01 ut, the swift burst alert telescope (bat) triggered and located grb 210824a (trigger=1070157). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 232.132, +11.135 which is ra(j2000) = 15h 28m 32s dec(j2000) = +11d 08' 07" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 50 sec. the peak count rate was ~1600 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 04:15:08.4 ut, 306.9 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 232.10513, 11.15208 which is equivalent to: ra(j2000) = 15h 28m 25.23s dec(j2000) = +11d 09' 07.5" with an uncertainty of 7.2 arcseconds (radius, 90% containment). this location is 113 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (3.31 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 8.5 (+5.30/-4.44) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 310 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.036. burst advocate for this burst is k. l. page (klp5 at leicester.ac.uk). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 210824a: swift detection of a burst |
we have analysed 4.8 ks of photon counting (pc) mode xrt data for the swift-bat-detected burst grb 230217a (moss et al. gcn circ. 33339), collected between t0+45.8 ks and t0+84.4 ks. two uncatalogued x-ray sources have been detected consistent with being within 296 arcsec of the swift-bat position, however none of them is above the rass limit or shows definitive signs of fading. therefore, at the present time we cannot identify which, if any, is the afterglow. details of these sources are given below: source 3: ra (j2000.0): 280.7700 = 18:43:4.80 dec (j2000.0): -28.8374 = -28:50:14.6 error: 4.7 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0144 [+0.0022, -0.0021] ct s^-1 distance: 67 arcsec from swift-bat position. flux: (6.48 [+0.98, -0.94])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 5: ra (j2000.0): 280.7763 = 18:43:6.30 dec (j2000.0): -28.7796 = -28:46:46.7 error: 6.4 arcsec (radius, 90% conf.) count-rate: (1.43 [+0.85, -0.64])e-3 ct s^-1 distance: 275 arcsec from swift-bat position. six uncatalogued sources were also detected too far from the grb position to be likely afterglow candidates. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/01154967. this circular is an official product of the swift-xrt team. | grb 230217a: swift-xrt observations |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 200412b (longo et al. gcn circ. 27557) in a series of observations tiled on the sky. the total exposure time is 4.9 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 1.5 ks. the data were collected between t0+20.1 ks and t0+31.7 ks, and are entirely in photon counting (pc) mode. two uncatalogued x-ray sources are detected, of which one ("source 2") is above the rass limit, and is therefore likely the grb afterglow. using 671 s of pc mode data and 2 uvot images, we find an enhanced xrt position (using the xrt-uvot alignment and matching uvot field sources to the usno-b1 catalogue): ra, dec = 278.31339, +62.53253 which is equivalent to: ra (j2000): 18h 33m 15.21s dec(j2000): +62d 31' 57.1" with an uncertainty of 2.5 arcsec (radius, 90% confidence). this position is 30.1 arcmin from the fermi/lat position. the light curve can be modelled with a power-law decay with a decay index of alpha=1.9 (+1.3, -1.2). a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 1.8 (+0.6, -0.5). the best-fitting absorption column is 1.6 (+1.8, -1.0) x 10^21 cm^-2, consistent with the galactic value of 5.1 x 10^20 cm^-2 (willingale et al. 2013). the counts to observed (unabsorbed) 0.3-10 kev flux conversion factor deduced from this spectrum is 3.1 x 10^-11 (3.8 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 1.6 (+1.8, -1.0) x 10^21 cm^-2 galactic foreground: 5.1 x 10^20 cm^-2 excess significance: <1.6 sigma photon index: 1.8 (+0.6, -0.5) if the light curve continues to decay with a power-law decay index of 1.9, the count rate at t+24 hours will be 0.015 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 kev flux of 4.7 x 10^-13 (5.8 x 10^-13) erg cm^-2 s^-1. the results of the xrt-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/xrt_products/tiled_grb00089/source2.php. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00089. this circular is an official product of the swift-xrt team. | grb 200412b: swift-xrt afterglow detection |
at 12:25:05 ut, the swift burst alert telescope (bat) triggered and located grb 221201a (trigger=1142847). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 266.933, -68.260 which is ra(j2000) = 17h 47m 44s dec(j2000) = -68d 15' 33" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single peak structure with a duration of about 40 sec. the peak count rate was ~5000 counts/sec (15-350 kev), at ~-13 sec after the trigger. (the peak occurred during a pre-planned slew and the nominal trigger time is the start of the first post-slew image.) the xrt began observing the field at 12:27:56.2 ut, 170.6 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 266.9228, -68.2510 which is equivalent to: ra(j2000) = 17h 47m 41.47s dec(j2000) = -68d 15' 03.6" with an uncertainty of 5.7 arcseconds (radius, 90% containment). this location is 35 arcseconds from the bat onboard position, within the bat error circle. no event data are yet available to determine the column density using x-ray spectroscopy. the initial flux in the 0.1 s image was 2.34e-08 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 202 seconds with the u filter starting 337 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.2 mag. data from the list of sources generated on-board are not available at this time. no correction has been made for the expected extinction corresponding to e(b-v) of 0.065. burst advocate for this burst is e. troja (nora.gsfc at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 221201a: swift detection of a burst |
gamma-ray bursts (grbs) are hosts to extreme environments and can serve as cosmological and physics probes. however, much of the physical origin and nature of these events are still unknown. the compton spectrometer and imager (cosi) will provide additional insight into grbs and their environments. cosi is a compact compton telescope sensitive to gamma-rays in the 0.2-5 mev energy range and is scheduled to launch in 2027 as the next nasa smex mission. cosi's inherent sensitivity to polarization and wide field of view uniquely situates it for spectroscopic and polarimetric studies of grbs from which we can gain insight into prompt emission mechanisms, jet structure, and the magnetic field geometry of the emission region. additionally, cosi's sub-degree localizations, afforded by compton imaging, coupled with its spectral and polarization capabilities will uniquely enable robust follow-up campaigns of grb afterglows and kilonovae. in this contribution we will discuss the grb science case and how cosi will enable this science. | studying gamma-ray bursts with cosi |
frb 121102, the first-known repeating fast radio burst (frb) source, is associated with a dwarf host galaxy and compact, persistent radio source. in an effort to find other repeating frbs, first j141918.9+394036 (hereafter first j1419+3940) was identified in a search for similar persistent radio sources in dwarf host galaxies. first j1419+3940 was subsequently identified as a radio transient decaying on timescales of decades, and it has been argued that it is the orphan afterglow of a long gamma-ray burst. first j1419+3940 and frb 121102's persistent radio source show observational similarities, though the latter appears to be stable in brightness. nonetheless, if they have similar physical origins, then first j1419+3940 may also contain a source capable of producing fast radio bursts. we report the non-detection of short-duration radio bursts from first j1419+3940 during 3.1 h of observations with the 110-m green bank telescope at both 2 and 6 ghz. first j1419+3940 is 11 times closer compared with frb 121102, and exhibits an optically-thin synchrotron spectrum above 1.4ghz; our search was thus sensitive to bursts more than 100 times weaker than those seen from frb 121102. we encourage future burst searches to constrain the possible presence of an frb-emitting source. although such searches are high-risk, any such detection could greatly elucidate the origins of the frb phenomenon. | no radio bursts detected from first j141918.9+394036 in green bank telescope observations |
at 06:37:56 ut, the swift burst alert telescope (bat) triggered and located grb 210308a (trigger=1036227). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 67.088, +37.411 which is ra(j2000) = 04h 28m 21s dec(j2000) = +37d 24' 39" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows a few overlapping peaks with a duration of about 15 sec. the peak count rate was ~6000 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 06:39:21.81 ut, 85.0 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with a position: ra, dec 67.076417, 37.435310 which is equivalent to: ra(j2000) = 04h 28m 18.34s dec(j2000) = +37d 26' 07.11" with an uncertainty of 4.3 arcseconds (radius, 90% containment). this location is 94 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. uvot took a finding chart exposure of 150 seconds with the white filter starting 94 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 04:28:17.73 = 67.07388 dec(j2000) = +37:26:02.0 = 37.43388 with a 90%-confidence error radius of about 0.63 arc sec. this position is 8.5 arc sec. from the center of the xrt error circle. the estimated magnitude is 18.57 with a 1-sigma error of about 0.15. no correction has been made for the expected extinction corresponding to e(b-v) of 1.295. burst advocate for this burst is v. d'elia (valerio.delia at ssdc.asi.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 210308a: swift detection of a burst with an optical counterpart |
merging neutron star binary systems have long been thought to be the source of short gamma-ray bursts: highly energetic and collimated jets. this model was recently confirmed with observations of gw170817, which involved an off-axis jet. as the jet interacts with the external medium it emits multi-wavelength radiation called the afterglow. here we test the viability of the open-source python package afterglowpy, developed by ryan et al. (2020), for producing off-axis afterglows consistent with the x-ray and radio data of gw170817. we compare the afterglowpy models with those presented by kathirgamaraju et al. (2019). lastly, we test the viability of implementing markov chain monte carlo methods to these models to scan the parameter space and produce a best fit curve for the observed afterglow. | exploring an afterglow flux code to model jets from binary neutron star mergers |
grb 210411c (trigger=1042398) with a redshift z=2.826 (a. de ugarte postigo et al, 2021, gcn29806) was triggered and located by swift burst alert telescope (bat) (t. sbarrato et al, 2021, gcn 29794) with t90=12.8 sec in 15-150 kev (c. b. markwardt et al, 2021, gcn29810). the corresponding luminosity light curves of swift-bat and swift-xrt (j.d. gropp et al, 2021, gcn29807) show this source is a twin of grb 190114c (ruffini et al, 2021, https://doi.org/10.1093/mnras/stab724). a new additional feature is identified in the early luminosity of swift-xrt data of grb 210411c (see enclosed fig.1). we recommend to check for the possible existence of a yet unobserved gev radiation and to follow up the late kev and possible gev temporal power-law luminosities. fig. 1: http://www.icranet.org/documents/swift_grb210411c-fermi_grb190114c.pdf | grb 210411c: a very significant early x-ray afterglow |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 221022a (aaron tohuvavohu et al. gcn circ. 32824), collecting 3.8 ks of photon counting (pc) mode data between t0+170.9 ks and t0+184.2 ks. six uncatalogued x-ray sources have been detected, however none of them is above the rass limit or shows definitive signs of fading. none of the six is inside the guano error region. therefore, at the present time we cannot identify which, if any, is the afterglow. details of these sources are given below: source 1: ra (j2000.0): 118.4349 = 07:53:44.38 dec (j2000.0): -5.2165 = -05:12:59.3 error: 7.7 arcsec (radius, 90% conf.) count-rate: (3.1 [+1.5, -1.2])e-3 ct s^-1 distance: 489 arcsec from swift/bat-guano position. source 2: ra (j2000.0): 118.3560 = 07:53:25.45 dec (j2000.0): -5.2797 = -05:16:47.0 error: 5.3 arcsec (radius, 90% conf. [enhanced position]) count-rate: (4.3 [+1.7, -1.4])e-3 ct s^-1 distance: 588 arcsec from swift/bat-guano position. flux: (1.12 [+0.45, -0.36])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 3: ra (j2000.0): 118.2368 = 07:52:56.83 dec (j2000.0): -5.2703 = -05:16:13.1 error: 6.1 arcsec (radius, 90% conf.) count-rate: (4.2 [+1.8, -1.4])e-3 ct s^-1 distance: 668 arcsec from swift/bat-guano position. flux: (2.14 [+0.91, -0.72])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 4: ra (j2000.0): 118.4804 = 07:53:55.29 dec (j2000.0): -5.1253 = -05:07:31.0 error: 6.9 arcsec (radius, 90% conf.) count-rate: (1.65 [+1.13, -0.80])e-3 ct s^-1 distance: 497 arcsec from swift/bat-guano position. source 5: ra (j2000.0): 118.1854 = 07:52:44.49 dec (j2000.0): -5.2601 = -05:15:36.4 error: 4.1 arcsec (radius, 90% conf. [enhanced position]) count-rate: (5.9 [+2.1, -1.7])e-3 ct s^-1 distance: 761 arcsec from swift/bat-guano position. flux: (2.22 [+0.79, -0.64])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 6: ra (j2000.0): 118.3078 = 07:53:13.87 dec (j2000.0): -5.2740 = -05:16:26.4 error: 6.6 arcsec (radius, 90% conf.) count-rate: (5.0 [+2.4, -1.8])e-3 ct s^-1 distance: 578 arcsec from swift/bat-guano position. flux: (1.01 [+0.47, -0.37])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021530. this circular is an official product of the swift-xrt team. | grb 221022a: swift-xrt observations |
at 22:41:20 ut, the swift burst alert telescope (bat) triggered and located grb 221226b (trigger=1145959). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 22.917, -41.554 which is ra(j2000) = 01h 31m 40s dec(j2000) = -41d 33' 13" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 10 sec. the peak count rate was ~2200 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 22:42:32.4 ut, 72.4 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 22.90890, -41.52648 which is equivalent to: ra(j2000) = 01h 31m 38.14s dec(j2000) = -41d 31' 35.3" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 101 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.69 x 10^20 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 75 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.017. burst advocate for this burst is s. b. cenko (brad.cenko at nasa.gov). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 221226b: swift detection of a burst |
we observed the location of the swift and fermi short grb 210323a (gropp et al., gcn 29699, hamburg et al., gcn 29709) with the gemini multi-object spectrograph (gmos) mounted on gemini-north. we obtained 15x90-sec imaging in r-band at a mid-time of 2021 march 24.637 ut (0.72 days post-burst). just to the east, outside of the updated xrt position (90% confidence; evans et al., gcn 29704), we detect faint emission consistent with the putative optical afterglow (malesani et al., gcn 29703, pozanenko et al, gcn 29708, de ugarte postigo et al., gcn 29717). however, there is also a clear extension from this position to the north, which we propose to be a faint underlying host galaxy. at present it is not possible to disentangle the contributions of faint afterglow and the underlying host. we measure a position for the source (or source complex) of ra = 21:11:47.34, dec = +25:22:10.1 (j2000; 0.5'' uncertainty), ~0.7-0.9'' offset from the mondy and not positions. after calibrating our stacked image to isolated stars detected in the ps1 photometric catalog (chambers et al., 2016), we perform aperture photometry of the entire extended source, and measure r = 24.6 +/- 0.2 ab mag (not corrected for milky way extinction). compared to the not and gtc measurements malesani et al., gcn 29703; de ugarte postigo et al., gcn 29717), this indicates fading of ~1.7 magnitudes over ~9.5 hours, indicating a rapid rate of decay of f~t^-1.86. this decline rate is likely contaminated by the host galaxy and the true decline rate is potentially steeper, consistent with the steep x-ray afterglow decline rate (beardmore et al., gcn 29705). further observations are planned to assess any variability of the source. we thank gemini staff joan font-serra and teo mocnik for the rapid scheduling and execution of these observations. | grb 210323a: gemini-north optical source detection |
we performed photometric observations of the afterglow of grb 221202a detected by the swift burst alert telescope (bat) at 20:06:10.56 ut (caputo et al., gcn 33005; de wet et al., gcn 33007; beardmore et al., gcn 33008; strausbaugh et al., gcn 33009; evans et al., gcn 33010) with the fors2 instrument at the eso vlt-ut1 in the r_special, i_bessel and z_gunn filters (in the following riz). the observation started at 06:50:29 ut (about 10.73 hours after the bat detection), and consisted of 500 s in r, 800 s in i, and 1320 s in z. we detect a source in the xrt error circle in all filters at position ra, dec. (j2000) = 05:08:19.94,-59:49:58.6, astrometrized against gaia dr3 field stars. we measure the following photometry, consistent with the upper limits of meerlicht (s. de wet et al., gcn 33007) and lcogt (r. strausbaugh et al., gcn 33009): r = 23.10 +/- 0.05 mag, i = 22.68 +/- 0.06 mag, z = 22.52 +/- 0.07 mag. magnitudes are calibrated against skymapper field stars and are in the ab system. for the r and i bands we use the lupton formulas to convert the standard stars to the bvri photometric system, then convert the measured magnitudes back to the ab system. a source at the same position is visible in r'-band images downloaded and stacked from the legacy imaging survey, with r' ~ 24.3 mag (ab). therefore, we conclude that the detected source is dominated by the afterglow of grb 221202a and slightly contaminated by the grb host galaxy. we derive an x-ray to optical slope beta_ox ~ 0.8, therefore the afterglow is not dark, just faint. we acknowledge the support provided by t. c. emy and the paranal staff, in particular ana escorza, ricardo arrue, marcela espinoza, and michael abdul-masih. | grb 221202a: vlt/fors2 afterglow discovery |
at 23:39:24 ut, the swift burst alert telescope (bat) triggered and located grb 221016a (trigger=1129775). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 38.949, -34.624 which is ra(j2000) = 02h 35m 48s dec(j2000) = -34d 37' 26" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single peak with tail structure with a duration of about 30 sec. the peak count rate was ~3500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 23:42:24.0 ut, 179.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 38.94479, -34.61039 which is equivalent to: ra(j2000) = 02h 35m 46.75s dec(j2000) = -34d 36' 37.4" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 50 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (3.53 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.8 (+3.14/-2.70) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 97 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.026. burst advocate for this burst is k. l. page (kimlpage1978 at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 221016a: swift detection of a burst |
"we initiated our afterglow monitoring campaign, consisting of two epic-pn observations, with the xmm-newton observatory on the short-duration grb 211106a (tohuvavohu et al., gcn #31049) on 2021 november 20 (22:37:51 ut) and 2021 december 8 (19:46:37 ut) ut, with median observation times of ~15 and ~33 days post-trigger. the two xmm-newton observations were obtained under the proposal 086286 (pi: fong), with effective exposure times of ~20 ks and ~47 ks, respectively. in the combined xmm-newton dataset, we detect the x-ray counterpart to grb 211106a at the position: ra(j2000) = 22h54m20.8s dec(j2000) = -53d13m50.9s with a total positional uncertainty of 1.7 arcsec (dominated by xmm-newton's systematic uncertainty). the xmm-newton position of the x-ray afterglow and the chandra position reported by berger et al. (2021, gcn #31145) are consistent with each other within the errors. the afterglow is detected in both epochs at a significance of ~5.5 sigma and ~3.4 sigma, with total net source counts of ~83 and ~73 (0.3-10 kev), respectively. the xrt, chandra and xmm-newton afterglow unabsorbed flux, starting at ~0.5 days post-burst, can be modeled with a single power-law decline characterized by a decay index (f~t^alpha) of alpha=-1.02 (-0.06,+0.05). additionally, from our jointly spectral fitting of both data sets, we derive an intrinsic neutral hydrogen absorption column of ~1.4e21 cm^2 for z=0.097 (malasani et al., gcn #31075; christensen et al., gcn #31075). we obtain higher inferred intrinsic column density for greater presumed source redshifts (kilpatrick et al., gcns #31146, #31157). we thank the xmm-newton project scientist, norbert shartel, and staff for the rapid planning and scheduling of these observations." | grb 211106a: xmm-newton monitoring campaign detections |
at 04:39:37 ut, the swift burst alert telescope (bat) triggered and located grb 200612a (trigger=977310). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 302.681, -45.357 which is ra(j2000) = 20h 10m 43s dec(j2000) = -45d 21' 24" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 40 sec. there is possible lower-level activity out to t+180s. the peak count rate was ~1400 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 04:41:04.7 ut, 87.7 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 302.7017, -45.3343 which is equivalent to: ra(j2000) = 20h 10m 48.41s dec(j2000) = -45d 20' 03.5" with an uncertainty of 5.1 arcseconds (radius, 90% containment). this location is 97 arcseconds from the bat onboard position, within the bat error circle. no event data are yet available to determine the column density using x-ray spectroscopy. the initial flux in the 2.5 s image was 2.13e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 95 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.03. we note that fermi-gbm sees a grb in a similar location at t+10 minutes, (trigger 613630183) which may be extended activity of the same source. at that time, bat had slewed away from the source. burst advocate for this burst is e. sonbas (edasonbas at yahoo.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200612a: swift detection of a burst |
studying the spectra of long gamma-ray bursts (grbs) is providing greater clues about the environments in which they reside. much of our understanding to date comes from spectral data obtained in the gamma-ray to x-ray. studies of the environments of individual bursts have additionally included uv/optical data. however, because of the paucity of uv/optical data in the past, the soft-energy component has not been systematically included in these studies. the swift ultra-violet/optical telescope (uvot) has observed more grbs in the uv/optical than any other telescope. from these observations we have generated a homogenous uv/optical grb afterglow catalog. coupling this data with archival swift x-ray telescope (xrt) data, we examine the spectral evolution of grbs in order to probe the circumburst environment. particularly we examine the fraction of grbs that have their cooling break between the optical and x-ray, and place limits on the number of bursts residing in a windy or ism environment. | a homogeneous dataset for probing the environments of gamma-ray bursts |
at 09:10:29 ut, the swift burst alert telescope (bat) triggered and located grb 220618a (trigger=1110821). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 38.966, +55.214 which is ra(j2000) = 02h 35m 52s dec(j2000) = +55d 12' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single peak structure with a duration of about 40 sec. the peak count rate was ~800 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 09:12:53.1 ut, 143.2 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 38.98802, 55.21543 which is equivalent to: ra(j2000) = 02h 35m 57.12s dec(j2000) = +55d 12' 55.5" with an uncertainty of 4.3 arcseconds (radius, 90% containment). this location is 45 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (4.74 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 8.9 (+7.86/-6.18) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 6.79e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 151 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the large, but uncertain, extinction expected. burst advocate for this burst is e. troja (nora.gsfc at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 220618a: swift detection of a burst |
at 03:52:28 ut, the swift burst alert telescope (bat) triggered and located grb 200917a (trigger=996184). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 235.753, -4.695 which is ra(j2000) = 15h 43m 01s dec(j2000) = -04d 41' 42" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single peak with a duration of about 15 sec. the peak count rate was ~1200 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 03:54:09.0 ut, 100.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 235.7247, -4.7011 which is equivalent to: ra(j2000) = 15h 42m 53.93s dec(j2000) = -04d 42' 04.0" with an uncertainty of 2.3 arcseconds (radius, 90% containment). this location is 103 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.49 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 5.6 (+5.36/-4.35) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 104 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.19. burst advocate for this burst is e. sonbas (edasonbas at yahoo.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200917a: swift detection of a burst |
at 10:03:40 ut, the swift burst alert telescope (bat) triggered and located grb 210807a (trigger=1064221). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 76.677, +58.245 which is ra(j2000) = 05h 06m 43s dec(j2000) = +58d 14' 43" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). because this is an image trigger, the actual light curve structure requires further ground data analysis. the 112-s image trigger indicates that this is a long burst. the xrt began observing the field at 10:07:02.3 ut, 201.9 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 76.6815, 58.2503 which is equivalent to: ra(j2000) = 05h 06m 43.56s dec(j2000) = +58d 15' 01.1" with an uncertainty of 11.1 arcseconds (radius, 90% containment). this location is 20 arcseconds from the bat onboard position, within the bat error circle. no event data are yet available to determine the column density using x-ray spectroscopy. the initial flux in the 2.5 s image was 4.08e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 210 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 05:06:43.90 = 76.68293 dec(j2000) = +58:14:59.2 = 58.24978 with a 90%-confidence error radius of about 0.61 arc sec. this position is 3.3 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.00 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.409. burst advocate for this burst is a. y. lien (amy.y.lien at nasa.gov). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 210807a: swift detection of a burst with an optical counterpart |
swift-xrt has performed follow-up observations of the maxi-detected burst grb 200517a (niwano et al. gcn circ. 27750) in a series of observations tiled on the sky. the total exposure time is 1.1 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 388 s. the data were collected between t0+8.0 ks and t0+8.3 ks, and are entirely in photon counting (pc) mode. an uncatalogued x-ray source is detected and is above the rass limit, and is therefore likely the grb afterglow. using 366 s of pc mode data and 2 uvot images, we find an enhanced xrt position (using the xrt-uvot alignment and matching uvot field sources to the usno-b1 catalogue): ra, dec = 17.69837, -50.92242 which is equivalent to: ra (j2000): 01h 10m 47.61s dec(j2000): -50d 55' 20.7" with an uncertainty of 3.3 arcsec (radius, 90% confidence). this position is 20.7 arcmin from the maxi position. we cannot determine at the present time whether the source is fading. the results of the xrt-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/xrt_products/tiled_grb00090/source1.php. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00090. this circular is an official product of the swift-xrt team. | grb 200517a: swift-xrt afterglow detection |
at 17:04:36 on 2021-06-21 ut, the swift burst alert telescope (bat) triggered on a burst from the soft gamma repeater swift j1555.2-5402 (trigger=1057131). swift was already observing the source at that time. the bat on-board calculated location is ra, dec 238.812, -54.063 which is ra(j2000) = 15h 55m 15s dec(j2000) = -54d 03' 45" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the immediately available bat light curve showed a single high bin on the 64 ms timescale, consistent with the on-board trigger duration of 8 milliseconds for a single short spike. the peak count rate was ~1000 counts/sec (15-350 kev) on the 64 ms timescale, at ~0 sec after the trigger. using promptly downlinked data we find an x-ray source with an enhanced position: ra, dec 238.7871, -54.0615 which is equivalent to: ra(j2000) = 15h 55m 08.90s dec(j2000) = -54d 03' 41.4" with an uncertainty of 2.0 arcseconds (radius, 90% containment), which is consistent with the position of swift j1555.2-5402. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data does not constrain the column density. uvot took a finding chart exposures of 150 seconds with the white filter and 250 seconds with the u filter. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18.0 mag. no correction has been made for the large, but uncertain, extinction expected. this source lies within the current (sector 39) field-of-view of tess camera 2. the current list of bursts from this source detected by bat now stands at: 2021-06-03 09:45:46 gcn #30120 (discovery) 2021-06-05 23:52:04 atel #14690 2021-06-07 12:33:40 atel #14690 2021-06-13 06:35:22 not previously reported 2021-06-16 14:44:30 not previously reported 2021-06-21 17:04:36 this gcn | swift trigger 1057131: detection of a burst from sgr swift j1555.2-5402 |
at 10:19:44 ut, the swift burst alert telescope (bat) triggered and located grb 230123a (trigger=1150429). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 40.937, -65.676 which is ra(j2000) = 02h 43m 45s dec(j2000) = -65d 40' 33" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single-peaked structure with a duration of about 10 sec. the peak count rate was ~800 counts/sec (15-350 kev), at ~1 sec after the trigger. the immediately available bat light curve does not include data from ~t+8 s to ~t+100 s. there might be additional burst emission in that time interval. the xrt began observing the field at 10:21:13.6 ut, 88.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 40.85977, -65.68672 which is equivalent to: ra(j2000) = 02h 43m 26.34s dec(j2000) = -65d 41' 12.2" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 120 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (2.95 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 1.3 (+1.44/-1.26) x 10^22 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 92 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 12% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.022. burst advocate for this burst is m. a. williams (mjw6837 at psu.edu). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 230123a: swift detection of a burst |
swift-xrt has performed follow-up observations of the maxi-detected burst grb 190708b (kawakubo et al. gcn circ. 25037) in a series of observations tiled on the sky. the total exposure time is 3.9 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 1.2 ks. the data were collected between t0+58.5 ks and t0+69.2 ks, and are entirely in photon counting (pc) mode. one uncatalogued x-ray source has been detected, it is below the rass limit and shows no definitive signs of fading. therefore, at the present time we cannot confirm this as the afterglow. details of this source are given below: source 1: ra (j2000.0): 326.4868 = 21:45:56.83 dec (j2000.0): +7.8821 = +07:52:55.5 error: 7.7 arcsec (radius, 90% conf.) count-rate: 0.0151 [+0.0054, -0.0044] ct s^-1 distance: 685 arcsec from maxi position. flux: (2.13 [+0.77, -0.62])e-12 erg cm^-2 s^-1 (observed, 0.3-10 kev) a catalogued source was also detected. the results of the xrt-team automatic analysis of the tiled xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/tiled_grb00080. this circular is an official product of the swift-xrt team. | grb 190708b: swift-xrt observations |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 211229a (tohuvavohu et al., gcn circ. 31334), also detected by fermi/gbm and gecam (fermi gbm team, gcn circ. 31329, zhao et al., gcn circ. 31331), collecting 5.0 ks of photon counting (pc) mode data between t0+43.6 ks and t0+66.8 ks. four uncatalogued x-ray sources have been detected consistent with being within 394 arcsec of the swift/bat-guano position, however none of them is above the rass limit or shows definitive signs of fading. therefore, at the present time we cannot identify which, if any, is the afterglow. details of these sources are given below: source 1: ra (j2000.0): 295.1317 = 19:40:31.60 dec (j2000.0): +23.1983 = +23:11:53.8 error: 6.3 arcsec (radius, 90% conf.) count-rate: (3.5 [+1.3, -1.0])e-3 ct s^-1 distance: 252 arcsec from swift/bat-guano position. flux: (2.78 [+1.01, -0.83])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 295.0615 = 19:40:14.76 dec (j2000.0): +23.2617 = +23:15:42.0 error: 9.7 arcsec (radius, 90% conf.) count-rate: (1.60 [+0.88, -0.66])e-3 ct s^-1 distance: 398 arcsec from swift/bat-guano position. source 5: ra (j2000.0): 295.0738 = 19:40:17.70 dec (j2000.0): +23.1573 = +23:09:26.3 error: 6.6 arcsec (radius, 90% conf.) count-rate: (2.12 [+0.97, -0.76])e-3 ct s^-1 distance: 20 arcsec from swift/bat-guano position. flux: (1.59 [+0.72, -0.57])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 6: ra (j2000.0): 295.1187 = 19:40:28.49 dec (j2000.0): +23.1638 = +23:09:49.7 error: 5.3 arcsec (radius, 90% conf.) count-rate: (2.94 [+1.13, -0.91])e-3 ct s^-1 distance: 151 arcsec from swift/bat-guano position. an uncatalogued source was also detected, however this was too far from the grb position to be the afterglow. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021475. no optical afterglow consistent with the guano position (tohuvavohu et al., gcn circ. 31334) is detected in the initial uvot exposures. preliminary 3-sigma upper limits using the uvot photometric system (breeveld et al. 2011, aip conf. proc. 1358, 373) for the initial exposures are: filter t_start(s) t_stop(s) exp(s) mag u 43722 66830 4882 >21.0 the magnitudes in the table are not corrected for the galactic extinction due to the reddening of e(b-v) = 5.811 in the direction of the burst (schlegel et al. 1998). this circular is an official product of the swift-xrt and uvot team. | grb 211229a: swift-xrt and uvot observations |
following the x-ray afterglow detection (gcn 28300) and the identification of possible optical transient (gcn 28295) spatially coincident with the x-ray source, we present a further analysis of the kw detection of the short-duration, soft-spectrum, bright grb 200826a (gcns 28284, 28287, 28288, 28289, 28294). as observed by kw the burst duration is t50=0.286+/-0.029 s (t90 = 0.772+/-0.188 s). the position of the grb 200826a in the hardness-duration diagram (logt50-loghr32) of 1610 kw bright grbs (svinkin et al., jphcs 1400, 2, 022010, 2019) suggests that the burst comes from the long/soft grb population. the figure showing the hardness-duration diagram is available at http://www.ioffe.ru/lea/grbs/grb200826_t16195/grb200826a_hrt50.png the contours denote the 1 and 3 sigma confidence regions for two-dimensional gaussian distributions. the hr32 is the ratio of counts in the 200-760 kev and 50-200 kev bands accumulated during burst duration. the vertical dashed line at t50=0.7 s marks the boundary used by svinkin et al. 2019 to distinguish between short and long kw grbs. assuming the redshift of an underlying galaxy z=0.714 (gcn 28295) and a standard cosmology model with h_0 = 67.3 km/s/mpc, omega_m = 0.315, and omega_lambda = 0.685 (planck collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release e_iso is ~4.7x10^51 erg, the peak luminosity l_iso is ~1.6x10^52 erg/s, and the rest-frame peak energy of the time-integrated spectrum, ep,i, is ~115 kev. with these values, grb 200826a is within the 1 sigma prediction band of both 'amati' and 'yonetoku' relations built for 138 type ii (long/soft) grbs with known z (tsvetkova et al., apj 850 161, 2017). meanwile, in both eiso-ep,z and liso-ep,z planes, the grb 200826a position is inconsistent with short-hard (type i) grb population, see http://www.ioffe.ru/lea/grbs/grb200826_t16195/grb200826a.pdf thus, from the analysis of the kw detection, we conclude, that, grb 200826a may be classified as type ii (long/soft, core-collapse origin). | grb 200826a: further analysis of the konus-wind data and classification |
the distribution of jet angles for short grbs is critical to constrainbecause it has direct implications for the true energy scale and eventrate, parameters of interest for gravitational wave detections. ourcurrent knowledge of the opening angle distribution comes from x-rayobservations >1 day after the burst. we propose xmm too observations tomonitor a short grb afterglow and constrain its collimation from the(non)detection of a jet break, to constrain or measure >5-20 deg. aprecise calculation of the angle also requires broad-band afterglowobservations; with our ongoing radio, optical/nir short grb too programs,our group is uniquely poised to provide the tightest constraints onthese angles. | late-time x-ray behavior of short grbs: implications for energetics and rates |
in this report we test for reliability any signatures of field galaxies clustering in the grb 021004 line of sight. the first signature is the bta and hubble grb 021004 field photometric redshift distribution with a peak at z ~ 0.5 estimated from multicolor photometry. the second signature is the mgii 2796,2803 absorption doublet at z ~ 0.5 in the grb 021004 afterglow spectrum. the third signature is some inhomogeneity in plank + grb 021004 fields. and the fourth signature may be the galaxy clustering with an effective redshift of z = 0.5 from the baryon oscillation spectroscopic survey (boss), which is a part of the sloan digital sky survey iii (sdss-iii). | clustering of galaxies around the grb 021004 sight-line at z ~ 0.5 |
the multi-messenger discovery of the neutron star merger gw170817 showed that nearby mergers may be common. however, this merger probably would have not been identified as nearby without its gravitational wave detection, raising the possibility that other nearby events may be hiding in plain sight. a possibility to uncover such nearby mergers from the past to search for their radio emission that can last for decades. here we discuss the possibility that the radio transient first j1419 +3940, first observed in 1993 and still detectable, could have originated from a neutron star merger. i will show that its observed radio light curve is well reproduced by a merger model with astrophysically expected parameters. i will discuss clues that could differentiate the transient's neutron star merger origin from the alternative explanation--the afterglow of an off-axis long gamma-ray burst. existing radio surveys likely already recorded multiple radio flares, informing us of the origin and properties of neutrons tar mergers and their role in the nucleosynthesis of the heaviest elements in the universe. | search for nearby neutron star mergers via radio flares |
leading models relate short gamma-ray bursts (sgrbs) to a relativistic jet launched by the black hole (bh)-accretion torus system that can be formed in a binary neutron star (bns) or a ns-bh binary merger. however, recent observations by swift have revealed a large fraction of sgrb events accompanied by x-ray afterglows with durations ~102 -105 s , suggesting continuous energy injection from a long-lived central engine, which is incompatible with the short (~ 1 s) accretion timescale of a bh-torus system. the formation of a supramassive ns (smns), resisting the collapse on much longer spin-down timescales, can explain these afterglow durations, but leaves serious doubts on whether a relativistic jet can be launched at merger. here we present a novel scenario that can solve this dichotomy, in which the sgrb is produced after the eventual collapse of the smns, but observed before (part of) its long-lasting spin-down emission. the ``time-reversal'' in the observation of the two signals is caused by the substantial delay affecting the spin-down emission, due to the optically thick environment surrounding the system generated by the early differential rotation and the subsequent spin-down emission itself. supported by miur fir grant no. rbfr13qjyf. | short gamma-ray bursts in the ``time-reversal'' scenario |
at 01:46:16 ut, the swift burst alert telescope (bat) triggered and located grb 200109a (trigger=948361). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 307.171, +53.003 which is ra(j2000) = 20h 28m 41s dec(j2000) = +53d 00' 12" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of 70 sec. the peak count rate was ~1600 counts/sec (15-350 kev), at ~2 sec after the trigger. the xrt began observing the field at 01:47:59.1 ut, 102.9 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source with an enhanced position: ra, dec 307.1258, 52.9932 which is equivalent to: ra(j2000) = 20h 28m 30.19s dec(j2000) = +52d 59' 35.5" with an uncertainty of 2.2 arcseconds (radius, 90% containment). this location is 104 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 3.98 x 10^21 cm^-2 (willingale et al. 2013). the initial flux in the 2.5 s image was 1.12e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 109 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.29. burst advocate for this burst is a. melandri (andrea.melandri at brera.inaf.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 200109a: swift detection of a burst |
tidal disruption events (tdes) are bursts of electromagnetic energy released when supermassive black holes (smbhs) at the centers of galaxies violently disrupt a star that passes too close. tdes provide a new window to study accretion onto smbhs; in some rare cases, this accretion leads to launching of a relativistic jet, but the necessary conditions are not fully understood. the best studied jetted tde to date is swift j1644+57, which was detected in gamma-rays more than a decade ago, but was too obscured by dust to be seen at optical wavelengths. i will present the discovery of at2022cmc, a rapidly fading source at redshift z~1.2 found in zwicky transient facility survey data, whose unique light curve transitioned into a luminous plateau within days. observations of an exceptionally bright counterpart at x-ray, sub-millimeter, and radio wavelengths supported the interpretation of at2022cmc as a rare jetted tde containing a synchrotron afterglow, likely launched by a rapidly spinning smbh. finally, i will discuss implications for rates and future prospects. | a luminous jetted tidal disruption event discovered by the ztf optical survey |
gamma-ray bursts (grbs) are brief flashes of gamma-rays occurring at an average rate of a few per day throughout the universe, and it is generally assumed that grb follows star formation rate. the ultimate energy source of a grb is believed to be associated with an exploding star that is in a process of forming a black hole, and a high amount of energy is expected to be released during this process. evidence of jetted grbs (jet opening-angle) can also be observed from radio and optical observations of achromatic breaks in the afterglow light curves. two different redshift (z) distributions were observed from different space observatories, the swift and preswift missions, however, the jet opening-angle distribution was determined only by the pre-swift satellites prior to 2007. le & dermer (2007) developed a flat grb spectrum model for long-duration grbs to fit the redshift (z) and the jet openingangle distributions measured with earlier grb missions, and showed that grbs do not follow star formation rate. however, their fitted results were obtained without using the opening-angle distribution from the swift sample. in this study we revisited the calculation done by le & dermer by refitting the redshift and the jet openingangle distribution measured from both pre-swift and swift satellites. we further explored how the broken power-law grb spectrum affect the overall fitting of the redshift and the jet opening-angle distributions, and the results will be presented in this paper. | on the redshift distribution of gamma-ray bursts in the swift era: revisited |
it is well know that some peculiar gamma-ray bursts have a low luminosity prompt phase. from this set of 2-3 events, it was derived what should be the general properties of these events, without statistical validations. we have constructed a sample of events with a low-luminosity afterglow phase in order to perform this statistical validation. we can confirm that this population is in general also faint in the prompt phase, albeit a few exceptions, and do not follow the amati relation. we have studied their intrinsic properties (spectral index, decay index, distance, luminosity, isotropic radiated energy and peak energy) to assess whether they belong to the same population than the brighter afterglow events. we can statistically validate the hypothesis previously done that these events belong to a population of nearby events, different from that of the general population of long gamma-ray bursts. last, we notice that about 65% of the confirmed gamma-ray burst-supernova associations belong to this group of faint events. while this is probably due to a selection effect, we discuss its consequence (these supernova templates should not be used blindly on normal long gamma-ray bursts). | a sample gamma-ray bursts with low luminosity afterglow to statistically derive their properties |
recent ground-based observations of tev photons have significantly deepened our understanding of the nature of gamma-ray bursts (grbs). however, many fundamental problems remain unsolved concerning the physical mechanisms behind grbs, necessitating the need for sufficient statistical data. the high altitude detection of astronomical radiation (hadar) experiment utilizes a wide-angle water cherenkov telescope, presenting a novel approach to measure the spectra and variability of grbs from 10 gev to 10 tev energy ranges with unprecedented photon statistics and thereby break new ground in elucidating the physics of grbs, which is still poorly understood. in this study, a time-dependent numerical modeling technique is utilized to simulate extensive light curves and spectral energy distributions of synthetic grb afterglow emissions. by harnessing the remarkable capabilities of hadar, we evaluate its potential in detecting grb afterglow emissions at energies >10 gev. through our analysis, we unveil the prospect of detecting an estimated 5.8 grbs annually, facilitating a systematic investigation into their reliance on model parameters. future hadar observations would offer valuable insights into the magnetic field and the environmental conditions surrounding grbs. | prospects for detecting γ-ray bursts at very high energies with the hadar experiment |
i will describe the not transient explorer (nte). nte is designed to be an instrument that can be permanently mounted (together with fies) at the not where it will allow that not to a powerful facility for follow-up observations of transient sources like supernovae, kilo novae, and afterglows of gamma-ray bursts. in addition, the instrument will provide capabilities requested from other interests in the user community. nte will allow spectroscopy from the uv to the k-band with resolution of about 4000 as well as simultaneous optical and near-ir imaging. spectropolarimetry is also part of the design. the nte project has been somewhat of an odyssey and i will also try to describe some of the scyllas and charybdisses we have encountered along the way. | the not transient explore: an odyssey |
at 19:46:13 ut, the swift burst alert telescope (bat) triggered and located grb 180504a (trigger=830822). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 331.134, -14.655 which is ra(j2000) = 22h 04m 32s dec(j2000) = -14d 39' 17" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 50 sec. the peak count rate was ~1000 counts/sec (15-350 kev), at ~5 sec after the trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 331.14235, -14.65988 which is equivalent to: ra(j2000) = 22h 04m 34.16s dec(j2000) = -14d 39' 35.6" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 3.50 x 10^20 cm^-2 (willingale et al. 2013). the initial flux in the 2.5 s image was 9.57e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 117 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.04. burst advocate for this burst is a. y. lien (amy.y.lien at nasa.gov). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/too.html.) | grb 180504a: swift detection of a burst |
the aim of this thesis is to find variable stars from the rotseiiid fields data files. in order to determine the variable stars, a simple but effective software, that works seamlessly, has been developed. robotic optical transient search experiment (rotse) is a worldwide project with four robotic telescopes, established in order to follow the optical afterglow radiation of the gamma-ray bursts (grb). in this study, the observations of the fields obtained from the rotseiiid telescope located in the tübi̇tak (scientific and technological research council of turkey) national observatory were used. rotseiiid creates a calibrated object list (cobj) from the observations gathered automatically. the different values of each star (ra, dec, pixel coordinates, m, merr, flags etc.) can be found in this generated list. in this thesis these values are extracted from data files. a php programme was developed in order to extract time series data of every star in a field. it also searches period, and if found, calculates phases for this data. the goal of this study is to determine the variable stars, especially unknown variables. ds9 and fv programs are used for dealing with fits files. also flowchart of program is given in this thesis. in addition debil (for finding some parameters of detached eclipsing binary stars) and gnuplot (for drawing graphics) are used by php program. using gnuplot, magnitude-time and period-time graphics of each star are plotted. the searching program is used for some different fields of rotseiiid data files. on the basis of the results of this research, 42 variable stars found and 14 of them are listed end of the thesis with their light curves. the data used in this thesis will be studied more detailed and research results of new/unknown variable stars will be published along the msc thesis. we are still studying on the data of new variable stars which were discovered by this research and the results will be published in near future... | skysurvey results of rotseiiid data |
on 14 september 2015, the laser interferometer gravitational-wave observatory (ligo) in a pre-operative testing state at the time detected its first sign of gravitational-waves. the ligo team sprang into action, performing data-quality checks on this unexpected signal. within two days, they had sent a notification to 63 observing teams at observatories representing the entire electromagnetic spectrum, from radio to gamma-ray wavelengths.illustration of a binary neutron star merger. the neutron stars 1) inspiral, 2) can produce a short gamma-ray burst, 3) can fling out hot, radioactive material in the form of a kilonova, and 4) form a massive neutron star or black hole with a possible remnant debris disk around it. [nasa/esa/a. feild (stsci)]thus began the very first hunt for an electromagnetic counterpart to a detected gravitational wave signal.what were they looking for?as two compact objects in a binary system merge, the system is expected to emit energy in the form of gravitational waves. if both of the compact objects are black holes, were unlikely to see any electromagnetic radiation in the process, unless the merger is occurring in an (improbable) environment filled with gas and dust.but if one or both of the two compact objects is a neutron star, then there are a number of electromagnetic signatures that could occur due to energetic outflows. if a relativistic jet forms, we could see a short gamma-ray burst and x-ray, optical, and radio afterglows. sub-relativistic outflows could produce optical and near-infrared signals, or a radio blast wave.timeline of observations of gw150914, separated by wavelength band, and relative to the time of the gravitational-wave trigger. the top row shows ligo information releases. the bottom four rows show high-energy, optical, near-infrared, and radio observations, respectively. click for a closer look! [abbott et al. 2016]surprise signalsince ligo and virgo (ligos european counterpart), wereprimarily expecting to detect binaries involving neutron stars, they set up a notification system to be able to quickly alert electromagnetic observatories of a gravitational-wave detection. those observatories would then be able to follow up on the gravitational-wave detectorsrough localization, with the goal of detecting the source by its electromagnetic signature.given that ligo had only just come online for testing when gw150914 was detected, its impressive that the pipeline was ready and there were observatories able to follow up so quickly! when the alert went out, 25 teams responded, mobilizing satellites and ground-based telescopes spanning 19 orders of magnitude in electromagnetic wavelength.the search partythe only information the teams were initially given was the localization of the signal to roughly 600 square degrees on the sky. with this starting point, over the next three months, these 25 facilities carefully observed the entirety of the estimated localization area.footprints of observations in comparison with the initial ligo localization of gw150914 (black contours). shown are radio fields (red), optical/infrared fields (green), and x-ray fields (blue circles); not shown are the all-sky fermi gbm, lat, integral spi-acs, and maxi observations. [abbott et al. 2016]some high-energy observatories, like fermi and integral, covered the whole sky. many optical facilities used a tiling strategy, together covering about 900 square degrees. still other observatories used a targeted approach, specifically looking at fields that contained a high density of nearby galaxies, in the hopes of detecting signs of a neutron-star merger or a core-collapse supernova.for the transient sources that were found, follow-up spectroscopy and further photometry was performed, to determine if the transient could have been the source of the detected gravitational waves.what was the outcome?no electromagnetic counterpart to gw150914 was found. it turns out this isnt surprising; gw150914 was later determined to have been the merger of two black holes, which should not generate an electromagnetic signature.so why report on this? in the publication prepared jointly by ligo, virgo, and these 25 teams (with one of the longer author lists youre likely to encounter!), the authors emphasize not the conclusion, but the process leading to it.in spite of the fact that ligo had not yet even begun its first observing run, the alert system worked, and the community mobilized to cover the entire 600 square degrees of sky with observations and follow-up characterization of candidate sources. if all this can be accomplished for an unexpected signal, imagine how well the system will work for future detections during actual science runs! with any luck, well be identifying the electromagnetic counterparts to gravitational-wave sources soon.citationb. p. abbott et al 2016 apj 826 l13. doi:10.3847/2041-8205/826/1/l13 | the hunt for a counterpart to gw150914 |
at 16:14:21 ut, the swift burst alert telescope (bat) triggered and located grb 230414b (trigger=1164180). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 181.071, +53.127 which is ra(j2000) = 12h 04m 17s dec(j2000) = +53d 07' 36" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 30 sec. the peak count rate was ~400 counts/sec (15-350 kev), at ~5 sec after the trigger. the xrt began observing the field at 16:16:29.8 ut, 128.6 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 181.09569, 53.15401 which is equivalent to: ra(j2000) = 12h 04m 22.97s dec(j2000) = +53d 09' 14.4" with an uncertainty of 3.8 arcseconds (radius, 90% containment). this location is 110 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.68 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 2.8 (+2.36/-2.05) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 133 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.017. burst advocate for this burst is a. d'ai (antonino.dai at inaf.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 230414b: swift detection of a burst |
gamma-ray bursts are bright enough to be seen to very great distances and their afterglows can provide redshifts and positions for their host galaxies, and in some cases details of the ism and the igm close to the burst, irrespective of the host magnitude itself. thus grbs, despite their small numbers, offer a unique and powerful tracer of early star formation and the galaxy populations in the era of reionization. our efforts to identify high-z grbs have been rewarded with the discoveries of grb 090423 and grb 120923a at spectroscopic redshifts of 8.2 and 7.9 respectively. however, it remains the case that some good candidate high-z grbs cannot be followed up quickly or deeply enough with ground-based ir spectroscopy, and indeed for others the ly-alpha break may fall in regions of the ir spectrum difficult to access from the ground. grb 090429b is an example, which had a photo-z of 9.4, but for which spectroscopy was curtailed due to bad weather. wfc3/ir on hst can obtain redshifts based on the location of the ly-alpha break via slitless grism spectroscopy to considerably deeper limits (and hence later times) than is possible from the ground, thus offering a solution to this problem. this proposal aims to continue to build the sample of z>7 grbs by obtaining spectroscopy for a candidate for which photometry suggests a very high redshift, but where the redshift could not be secured from the ground. we also propose to monitor the afterglow of up to one z>7 grb found, to allow comparison with the lower redshift population of bursts, and to perform an initial search for its host. the low rate of z>7 grbs leads us to request a long-term too program, spanning cycles 23 and 24. | identifying and studying gamma-ray bursts at very high redshifts |
at 12:06:28 ut, the swift burst alert telescope (bat) triggered and located grb 230510a (trigger=1167973). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 318.156, +34.443 which is ra(j2000) = 21h 12m 37s dec(j2000) = +34d 26' 33" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 60 sec. the peak count rate was ~5100 counts/sec (15-350 kev), at ~13 sec after the trigger. the xrt began observing the field at 12:07:31.9 ut, 63.4 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 318.1314, 34.4424 which is equivalent to: ra(j2000) = 21h 12m 31.54s dec(j2000) = +34d 26' 32.6" with an uncertainty of 6.5 arcseconds (radius, 90% containment). this location is 73 arcseconds from the bat onboard position, within the bat error circle. no event data are yet available to determine the column density using x-ray spectroscopy. the initial flux in the 0.1 s image was 1.19e-08 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 72 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.144. this trigger was initially marked as matching a source in the bat ground catalogue: igr j21117+3427, a known gamma-ray source. however, the xrt localisation is more than 9 arcmin from the known position of igr j21117+3427, outside its error region of 3.5 arcmin (atel 873). this, together with the bat transient monitor light-curve showing little sign of variation suggests that this is in fact a new grb. burst advocate for this burst is r. a. j. eyles-ferris (raje1 at leicester.ac.uk). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 230510a: swift detection of a burst |
recent years have seen massive breakthroughs in the observations of gamma-ray bursts and other high-energy astrophysical transients. dynamical jet simulations have pro- gressed to a point where it is now becoming possible to fully numerically resolve gamma- ray burst (grb) jet evolution across scales. however, the modeling of radiative emis- sion is currently lagging behind and makes for a bottleneck severely limiting our efforts to fully interpret the physics of grbs in the multi-messenger era. in this thesis, i present new numerical developments to resolve this discrepancy and focus on providing insights into grb afterglow physics. using numerical simulations, i set out to under- stand the impact of the presence of multiple emission sites on afterglow light curves. i also investigate the trans-relativistic evolution of the jet and poorly understood be- haviour of the spectral breaks in the radiation as the jet decelerates. in order to do this, i develop a new method for the local numerical calculation of non-thermal emission in relativistic shocks. this method combines a moving mesh finite-volume code with the a local description of particle acceleration and corresponding synchrotron process. in or- der to inform the theoretical models to simulate, i investigate the grb x-ray afterglow sample variability using machine-learning-based data visualisation techniques. | numerics and theory of high-energy relativistic astrophysical transients |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 220107b (arimoto et al. gcn circ. 31409) in a series of observations tiled on the sky. the total exposure time is 1.3 ks, distributed over 2 tiles; the maximum exposure at a single sky location was 1.0 ks. the data were collected between t0+35.7 ks and t0+36.2 ks, and are entirely in photon counting (pc) mode. an uncatalogued x-ray source is detected and is above the rass 3-sigma upper limit at this position, and is therefore likely the grb afterglow. using 546 s of pc mode data and 1 uvot image, we find an enhanced xrt position (using the xrt-uvot alignment and matching uvot field sources to the usno-b1 catalogue): ra, dec = 216.40652, +20.17064 which is equivalent to: ra (j2000): 14h 25m 37.56s dec(j2000): +20d 10' 14.3" with an uncertainty of 3.4 arcsec (radius, 90% confidence). this position is 11.5 arcmin from the fermi/lat position. the source has a mean count rate of 1.3e-01 ct/sec; while we cannot determine at the present time whether it is fading, the fact that the source is well above rass limit strongly suggests it is the x-ray afterglow of grb 220107b. more data are currently being collected. the results of the xrt-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/xrt_products/tiled_grb00103/source1.php. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00103. this circular is an official product of the swift-xrt team. | grb 220107b: swift-xrt afterglow detection |
instruments such as the rotse, tortora, pi of the sky, master-net, and others have recorded single-band optical flux measurements starting as early as ~ 10 s after the gamma-ray trigger. the earliest measurements of optical spectral shape have been made only much later, on hour time scales, never on the time scale approaching a few minutes or less, until now. we began observations of grb201015a beginning only 58 seconds after the swift bat trigger, measuring simultaneously in three filter bands, g', r', and i', using the burst simultaneous three-channel imager (bsti, see grossan & maksut 2020) instrument on the nazarbayev university transient telescope at assy-turgen astrophysical observatory (nuttela-tao). we observed the afterglow peak and a power law temporal decay, t-α , with α1 =1.2±0.07 bewteen 500 and 1600 seconds, but later this changed to a value of α2 =0.8±0.1 between 1900 and 4000 seconds. the spectrum between the three filters was consistent with a power law fν ∝ ν-β with a value of β of 0.73±0.08 at the peak, 130 to 500 seconds, and 0.42±0.14 during the "early afterglow" phase, 500 to 1600 seconds, and 0.01±0.11 during the later afterglow phase, 1900 to 4000 seconds (we assumed a galactic reddening of 1.12, 0.77 and 0.58 mags, and source reddening of 0.19, 0.14 and 0.11 mags for the sloan g', r' and i' filters, respectively). we measured the x-ray temporal decay index of 0.8 ±0.1 which is consistent with our late optical temporal decay index and chandra x-ray decay index reported by gompertz et al. (2020). changes from one power law decay time and spectral index to another in this phase of the afterglow have been attributed to jet components of different angular extent dominating emission at different times (e.g. racusin et al. 2008), or the transition from reverse shock emission dominance to forward shock dominance (e.g. vestrand et al. 2014, racusin et al. 2008, wozniak et al. 2009, bloom et al. 2009); we discuss the relative merits of these scenarios in the body of this work. the changes we see in spectral shape in early afterglows suggest that significant information about this emission phase (and possibly prompt emission, if observed early enough) is being missed without such fast (sub-minute) response observations with simultaneous multi-color instruments. | early-time colour variations in the grb 201015a afterglow |
we discuss the synchrotron emission of fast cooling electrons in shocks. the fast cooling electrons behind the shocks can generate a position-dependent inhomogeneous electron distribution if they do not have enough time to mix homogeneously. this can lead to a very different synchrotron spectrum in low-frequency bands from that in the homogeneous case, due to the synchrotron absorption. in this paper, we calculate the synchrotron spectrum in the inhomogeneous case in a gamma-ray burst (grb). both the forward shock and the reverse shock are considered. we find that for the reverse shock dominated case, we would expect a “reverse shock bump” in the low-frequency spectrum. the spectral bump is due to the combination of synchrotron absorption in both the forward and reverse shock regions. in the low frequencies the forward shock spectrum has two unconventional segments, with spectral slopes of ≲ 1 and 11/8. the slope of 11/8 has been found by some authors, while the slope of ≲ 1 is new and due to the approximately constant electron temperature in the optically thick region. in the future, simultaneous observations in multiple bands (especially in the low-frequency bands) in the grb early afterglow or prompt emission phases will possibly reveal these spectral characteristics and enable us to identify the reverse shock component and distinguish between the forward and reverse shock emissions. this also may be a method with which to diagnose the electron distribution status (homogeneous or inhomogeneous) after fast cooling in the relativistic shock region. | synchrotron spectrum of fast cooling electrons in grbs |
at 19:03:04 ut, the swift burst alert telescope (bat) triggered and located grb 210305a (trigger=1035922). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 319.814, +34.557 which is ra(j2000) = 21h 19m 15s dec(j2000) = +34d 33' 24" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 100 sec. the peak count rate was ~3200 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 19:04:21.28 ut, 76.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with position: ra, dec 319.80764, 34.554389 which is equivalent to: ra(j2000) = 21h 19m 13.83s dec(j2000) = +34d 33' 15.8" with an uncertainty of 4.7 arcseconds (radius, 90% containment). this location is 21 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received. uvot took a finding chart exposure of 150 seconds with the white filter starting 85 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.155. burst advocate for this burst is a. d'ai (antonino.dai at inaf.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 210305a: swift detection of a burst |
gamma-ray bursts are bright enough to be seen to very great distances and their afterglows can provide redshifts and positions for their host galaxies, and in some cases details of the ism and the igm close to the burst, even for very faint hosts that are otherwise undetectable. thus grbs, despite their small numbers, offer a unique and powerful tracer of early star formation and the galaxy populations through the era of reionization. efforts to identify high-z grbs have been rewarded with the discoveries of grb 090423 and grb 120923a at spectroscopic redshifts of 8.2 and 7.8 respectively. however, it remains the case that some good candidate high- z grbs cannot be followed up quickly or deeply enough with ground-based ir spectroscopy, and indeed for others the ly-alpha break may fall in regions of the ir spectrum difficult to access from the ground. grb 090429b is an example, which had a photo-z of 9.4, but for which spectroscopy was curtailed due to bad weather. wfc3/ir on hst can obtain redshifts based on the location of the ly-alpha break via slitless grism spectroscopy to considerably deeper limits (and hence later times) than is possible from the ground, thus offering a solution to this problem. this proposal aims to build the sample of z>7 grbs by obtaining spectroscopy for up to two candidates for which photometry suggests a very high redshift, but where the redshift could not be secured from the ground. this will provide an important legacy of host galaxy targets with known redshifts for study with next generation facilities. the low rate of z>7 grbs leads us to request a long-term too program, spanning cycles 27 and 28. | identifying gamma-ray bursts at very high redshifts |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 210520a (di lalla et al. gcn circ. 30062) in a series of observations tiled on the sky. the total exposure time is 5.6 ks, distributed over 19 tiles; the maximum exposure at a single sky location was 649 s. the data were collected between t0+43.1 ks and t0+62 ks, and are entirely in photon counting (pc) mode. two uncatalogued x-ray sources are detected above the rass 3-sigma upper limit at this position, matching the afterglow criteria. however, none of them shows definitive signs of fading, and both of them are consistent with 2mass objects within the xrt error circle. therefore, none of them is likely the afterglow. details of these sources are given below: source 2: ra (j2000.0): 122.12040 = 08:08:28.90 dec (j2000.0): -69.7668 = -69:46:00.5 error: 7.7 arcsec (radius, 90% conf.) count-rate: (1.95 [+1.19, -0.85])e-2 ct s^-1 distance: 28.7' from fermi/lat position. source 3: ra (j2000.0): 124.47176 = 08:17:53.22 dec (j2000.0): -69.2963 = -69:17:46.8 error: 8.6 arcsec (radius, 90% conf.) count-rate: (3.0 [+1.6, -1.1])e-2 ct s^-1 distance: 31.8' from fermi/lat position. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00099. this circular is an official product of the swift-xrt team. | grb 210520a: swift-xrt observations |
swift-xrt has performed follow-up observations of the maxi-detected burst grb 220506a (urabe et al. gcn circ. 32001) in a series of observations tiled on the sky. the total exposure time is 1.2 ks, distributed over 6 tiles; the maximum exposure at a single sky location was 463 s. the data were collected between t0+38.2 ks and t0+55.6 ks, and are entirely in photon counting (pc) mode. an uncatalogued x-ray source is detected and is above the rass 3-sigma upper limit at this position, and is therefore likely the grb afterglow. the position of this source is ra, dec=239.7257, -26.4186 which is equivalent to: ra (j2000): 15:58:54.18 dec(j2000): -26:25:06.9 with an uncertainty of 7.2 arcsec (radius, 90% confidence). this position is 15.0 arcmin from the maxi position. we cannot determine at the present time whether the source is fading. the results of the xrt-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/xrt_products/tiled_grb00105/source1.php. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00105. this circular is an official product of the swift-xrt team. | grb 220506a: swift-xrt afterglow detection |
the almost simultaneous observation of gravitational waves and gamma-rays from gw170817 proved that binary neutron star mergers are associated with short gamma-ray bursts. however, it is still unclear wheter gw170817 was a misaligned short grb or a weak, spherical outflow. chandra observations and a detailed modeling of the afterglow are key to pinning down the nature of gw170817. we propose to develop a code to study the key characteristics of afterglows from binary neutron star mergers, including the polar structure of the jet, radial stratification of the ejecta, and a high energy cutoff in the electrons' distribution. the code will produce images, spectra, polarization, and light curves that will be fundamental in interpreting chandra data of gw170817 and other ligo mergers. | the afterglows of binary neutron star mergers: telling a jet from a balloon |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 190610a (palmer et al. gcn circ. 24783), collecting 5.0 ks of photon counting (pc) mode data between t0+292.3 ks and t0+300.5 ks. one uncatalogued x-ray source has been detected consistent with being within 187 arcsec of the swift/bat position, it is below the rass limit and shows no definitive signs of fading. therefore, at the present time we cannot confirm this as the afterglow. details of this source are given below: source 7: ra (j2000.0): 46.2216 = 03:04:53.17 dec (j2000.0): -7.6824 = -07:40:56.7 error: 5.3 arcsec (radius, 90% conf. [enhanced position]) count-rate: (1.76 [+0.83, -0.64])e-3 ct s^-1 distance: 111 arcsec from swift/bat position. flux: (1.17 [+0.55, -0.42])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) we note that the position of this afterglow candidate is consistent with the galaxy sdss j030452.77-074055.3 (r=21.5 ab), which has unknown redshift. five uncatalogued sources were also detected too far from the grb position to be likely afterglow candidates. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/too_grbs/00020896. this circular is an official product of the swift-xrt team. | grb 190610a: swift-xrt observations |
at 17:36:50 ut, the swift burst alert telescope (bat) triggered on swift j1818.0-1607 (trigger=969823). swift slewed immediately to the source. the bat on-board calculated location is ra, dec 274.498, -16.152, which is ra(j2000) = 18h 18m 00s dec(j2000) = -16d 09' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows a single spike with a duration of about 0.3 sec. the peak count rate was ~1200 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 17:37:52.5 ut, 62.6 seconds after the bat trigger. using promptly downlinked data we find an x-ray source with an enhanced position: ra, dec 274.5008, -16.1312 which is equivalent to: ra(j2000) = 18h 18m 00.18s dec(j2000) = -16d 07' 52.3" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 75 arcseconds from the bat onboard position, within the bat error circle, and consistent with the known position of swift j1818.0-1607. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.35 x 10^22 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 65 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the large, but uncertain, extinction expected. this source was first reported on 2020 march 12 (gcn #27373; evans et al.) since then it has been monitored every 3-7 days with swift follow-up observations. | swift detection of a burst from sgr swift j1818.0-1607 |
at 13:09:59 ut, the swift burst alert telescope (bat) triggered and located grb 211211a (trigger=1088940). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 212.272, +27.884d which is ra(j2000) = 14h 09m 05s dec(j2000) = +27d 53' 01" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). due to a telemetry dropout, the immediately available bat lightcurve starts at t+8s, and shows a bright complex burst that extends at least to t+100s. at t+8s the count rate is 300k counts/sec (15-350 kev), but the earlier peak may be significantly higher. the xrt began observing the field at 13:11:18.7 ut, 79.2 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 212.2912, 27.8899 which is equivalent to: ra(j2000) = 14h 09m 9.89s dec(j2000) = +27d 53' 23.6" with an uncertainty of 5.0 arcseconds (radius, 90% containment). this location is 64 arcseconds from the bat onboard position, within the bat error circle. no event data are yet available to determine the column density using x-ray spectroscopy. uvot took a finding chart exposure of nominal 150.000 seconds with the white filter starting 87 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. data from the 2.7'x2.7' sub-image are not available at this time. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.018. burst advocate for this burst is a. d'ai (antonino.dai at inaf.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 211211a: swift detection of a bright burst |
gamma-ray bursts (grbs) categorically produce broadband afterglow emission, but in some cases, emission in the optical band is less luminous than expected. the phenomenon of optical darkness has been studied extensively in long grbs (related to massive stellar explosions), with a number of proposed explanations, including high redshift and host galaxy extinction. investigations into optical darkness in short grbs (resulting from compact object binary mergers) have thus far been limited. this work implements an automated data analysis routine for determining the optical darkness of grbs, which is based on spectral indices calculated from temporally-matched swift-xrt data and ground-based follow-up observations. the pipeline produces a complete catalog of potential optically dark short grbs. in the process of this analysis, we develop a versatile codebase that facilitates reproducibility of the processing pipeline for use on future grbs. here we present the results of our study and outline some of the possible explanations for optical darkness in short grbs. our analysis tools and resulting complete sample of dark short grbs enable a systematic statistical study of the dark gamma-ray burst population, which—together with an exploration of the specific circumstances of each new grb we identify as dark—provide new insight into the phenomenon and its origins. | optical darkness in short-duration gamma-ray bursts |
the luminous, high-energy emission of gamma-ray bursts (grbs) makes them efficient probes of the high-redshift universe. the origin of the obscuration of gamma-ray burst afterglow is still unclear. we study the afterglows metal column densities along the line-of-sight of all swift-detected long grbs with an improved hierarchical bayesian analysis methodology. we characterise follow-up biases and side-step them using shoals, an unbiased sub-sample with highly complete follow-up. that survey also measures spitzer host masses. overall, the column densities shows little redshift evolution but a significant correlation with host stellar mass. a simple geometrical model explains the width and shape of the column density distribution and the trend with galaxy mass correlation. our findings implicate the host's galaxy-scale metal gas as the dominant obscurer. from a galaxy evolution perspective, our study places new constraints on the metal gas mass inside galaxies at z=0.5-4. we compare these with modern cosmological simulations (illustris and eagle) and discuss implications for the obscuration of other sources inside high redshift galaxies, such as active galactic nuclei. | host galaxies are the obscurers of gamma-ray bursts |
the swirling disks of material that surround supermassive black holes are likely home to massive stars, neutron stars, and black holes. a new study explores whether we can detect the signatures of fiery explosions produced by these uniquely situated stars and stellar remnants.an unusual homeartists illustration of two merging black holes embedded in the gas disk surrounding a supermassive black hole. [caltech/r. hurt (ipac)]recently, scientists detected gravitational waves from the merger of unexpectedly large black holes. one proposed explanation that these monsters grew to their large sizes while embedded within the accretion disk surrounding an even larger supermassive black hole has piqued interest in studying the evolution of stars hosted within the violent disks of these active galactic nuclei (agn).agn accretion disks are dense, turbulent environments that produce bright, high-energy radiation as disk material spirals inwards toward the black hole. yet these seemingly hostile surroundings may still host stars that arise either in situ the gas within accretion disks can become unstable and fragment into self-gravitating clumps that become stars or are captured from the nuclear star cluster that surrounds an agn.explosive endsonce stars form or are trapped in an agn disk, the dense environment increases the likelihood that the stars pair off into binaries. as disk-hosted stars evolve, some fraction of them should end their lives in spectacular explosions either as long gamma-ray bursts (grbs) caused by the deaths of massive stars, or as short grbs produced when two evolved stellar remnants collide.schematic illustrating the location of an exploding star in an agn disk, shown in cross section. bottom: illustration of relevant radii in observed grbs. ris is the location of internal shocks that usually powers prompt emission, and res marks the location where the expanding outflow runs into the surrounding medium, powering the afterglow. the relative locations of these radii can change in a dense surrounding environment, leading to different emission signatures. [perna et al. 2021]the possibility of these relativistic explosions occurring within agn disks is intriguing. does the unique environment of the disk influence the explosion? if so, could we expect to see specific, identifiable features from grbs produced within the disks around supermassive black holes?a team of scientists led by rosalba perna (stony brook university and flatiron institute) has explored these questions by modeling how the properties of grb explosions are changed when they occur within disks.searching for signaturesperna and collaborators explore a standard model of a grb in which prompt emission is produced first as a series of internal shocks are driven by colliding shells of speeding material. the prompt emission is then followed by a long, decaying afterglow as this relativistic outflow is slowed when it plows into the surrounding matter.the authors show that the properties of the agn disk environment can change the behavior of both of those emission components. the high density of the disk material can cause a powerful reverse shock to be driven backwards early in the explosion, powering the prompt emission in place of internal shocks. and the later afterglow of the grb can end up brighter and peaking earlier than is the case for typical grbs observed in a low-density environment like the interstellar medium.these features and other signatures identified by perna and collaborators may help us to determine whether future observed grbs exploded in typical environments, or instead in the extreme surroundings of an agn disk. this will help us to better understand how some stars may be evolving in their unusual homes around supermassive black holes.citationelectromagnetic signatures of relativistic explosions in the disks of active galactic nuclei, rosalba perna et al 2021 apjl 906 l7. doi:10.3847/2041-8213/abd319 | exploding stars in black hole disks |
grb 230409b was detected by the swift burst alert telescope (bat) at 04:56:57 ut on 9th april 2023 (beardmore et al., gcn 33592). the prompt emission mask-weighted bat light curve consists of a single-peaked structure with a t90 duration of 9.79 +- 2.59 sec in 15-350 kev energy range (palmer et al., gcn 33598). we compare the reported value of bat fluence and peak photon flux for this grb (palmer et al., gcn 33598) with all the bat-detected grbs sample; this burst is positioned at the middle-near top of this distribution. we also determine the peak energy of the burst using bat energy fluence and peak energy correlation. we calculated the peak energy of the burst is 61.49 (+23.39, -16.96) kev; the softer value of peak energy is consistent with those of long grbs (type ii). the swift xrt detected an x-ray afterglow ~ 101.2 sec after the bat trigger (beardmore et al., gcn 33592). the xrt count-rate light curve could be best described with a broken power-law model with temporal indices of 0.62 (+0.12, -0.12) and 1.15 (+0.19, -0.18) before and after break time (~4600-sec post-bat detection), respectively. as no redshift has been reported for this source, we modeled the late time time-averaged xrt spectrum (t0 + 18528 to 113195 sec) considering redshift = 2, roughly average redshift value for long grbs (type ii). the spectrum could be modeled using an absorption power-law with the following spectral parameters: nh_host= 4.85 (-4.85,+8.76) x 10^{22} cm^{-2} and \beta_x= 0.73 (-0.36,+0.40). considering the adiabatic deceleration without energy injection, closure relations indicate that the late time x-ray afterglow could be best described with \nu_m < \nu < \nu_c spectral regime for ism medium for the electron energy index p ~ 2.46. the swift uvot detected a weak fading source within the xrt error circle (kuin et al., gcn 33595). we performed the follow-up observations of this fading optical source using the tanspec mounted at the axial port of the 3.6m devasthal optical telescope (dot) of aries nainital at multiple epochs in j filter (near-infrared). we report the preliminary brightness of the afterglow to be j = 20.1 +/- 0.3 mag ~ 0.75 days after the bat trigger. we obtained the limiting mag of 20.5 mag ~ 2.7 days post-burst at successive epochs. our observations confirm this fading source to be the afterglow of grb 230409b. the magnitude values reported are calibrated against 2mass nearby stars. this circular may be cited. 3.6m devasthal optical telescope (dot) is the recently commissioned facility in the northern himalayan region of india (long:79 41 04e, lat:29 21 40n, alt:2540m) owned and operated by the aryabhatta research institute of observational sciences (aries), nainital ( https://www.aries.res.in). authors of this gcn circular thankfully acknowledge consistent support from the staff members to run and maintain the 3.6m dot. we also thank director aries for approving the ddt slot for the too observations. | grb 230409b: 3.6m dot near-infrared detection, afterglow confirmation |
swift-xrt has performed follow-up observations of the ipn-detected burst grb 230616a in a series of observations tiled on the sky. the total exposure time is 4.6 ks, distributed over 4 tiles; the maximum exposure at a single sky location was 2.0 ks. the data were collected between t0+111.3 ks and t0+140.7 ks, and are entirely in photon counting (pc) mode. three uncatalogued x-ray sources have been detected, however none of them is above the rass limit or shows definitive signs of fading. therefore, at the present time we cannot identify which, if any, is the afterglow. details of these sources are given below: source 1: ra (j2000.0): 192.1005 = 12:48:24.12 dec (j2000.0): +5.4365 = +05:26:11.4 error: 8.2 arcsec (radius, 90% conf.) count-rate: 0.0177 [+0.0053, -0.0045] ct s^-1 distance: 1675 arcsec from ipn position. flux: (6.8 [+2.1, -1.7])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 192.2299 = 12:48:55.18 dec (j2000.0): +6.0936 = +06:05:36.9 error: 5.1 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0125 [+0.0046, -0.0037] ct s^-1 distance: 820 arcsec from ipn position. flux: (4.2 [+1.5, -1.3])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 3: ra (j2000.0): 191.8031 = 12:47:12.74 dec (j2000.0): +5.5136 = +05:30:48.9 error: 6.0 arcsec (radius, 90% conf.) count-rate: (5.7 [+3.5, -2.5])e-3 ct s^-1 distance: 1769 arcsec from ipn position. the results of the xrt-team automatic analysis of the tiled xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/tiled_grb00112. this circular is an official product of the swift-xrt team. | grb 230616a: swift-xrt observations |
the digitised first byurakan survey (dfbs) provides low dispersion optical spectra for about 24 million sources. a two-step machine learning algorithm based on similarities to predefined templates is applied to select different classes of rare objects in the dataset automatically, for example late type stars, quasars and white dwarves. identifying outliers from the groups of common astrophysical objects may lead to discovery of rare objects, such as gamma-ray burst afterglows. | automatic source classification in digitised first byurakan survey |
we modelled dust grain-size distributions for carbonaceous and silicates dust, as well as for free-flying iron nanoparticles in the environment of a γ-ray burst (grb) afterglow, grb 180325a. this grb, at a redshift ($z$) of 2.2486, has an unambiguous detection of the 2175 å extinction feature with rv = 4.58 and av = 1.58 mag. in addition to silicates, polycyclic aromatic hydrocarbons (pah), and graphite, we used iron nanoparticles grain-size distributions for the first time to model the observed extinction curve of grb 180325a. we fit the observed extinction for four model permutations, using 232 sets of silicates, graphite, carbon abundance in hydrocarbon molecules (bc), and fraction of iron abundance in free-flying nanoparticles (yfe). these four different permutations were chosen to test iron nanoparticles significance and carbon abundance in hydrocarbons. our results indicate that iron nanoparticles contribution is insignificant and there is a degeneracy of carbon abundances, with the range (0.0 ≤ bc ≤ 0.7) × 10-5 providing the best-fit to the observed extinction curve of grb 180325a. we therefore favour the simplest model of silicates and pahs. the silicates are dominant and contribute to the entire wavelength range of the grb extinction curve while graphite contributes towards both the 2175 å bump and the ultraviolet (uv) extinction. the afterglow peak luminosity (1.5 × 1051 erg s-1) indicates dust destruction may have taken place. we conclude that further investigations into other potential contributors of extinction are warranted, particularly for steep uv extinction. | grb 180325a: dust grain-size distribution and interstellar iron nanoparticles contribution |
at 11:11:52 ut, the swift burst alert telescope (bat) triggered and located grb 220930a (trigger=1125809). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 64.737, +13.352 which is ra(j2000) = 04h 18m 57s dec(j2000) = +13d 21' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 20 sec and a secondary peak at about 70 seconds after the trigger time. the peak count rate was ~3000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 11:14:42.1 ut, 170.0 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 64.7149, 13.3500 which is equivalent to: ra(j2000) = 04h 18m 51.58s dec(j2000) = +13d 21' 00.0" with an uncertainty of 5.0 arcseconds (radius, 90% containment). this location is 77 arcseconds from the bat onboard position, within the bat error circle. no event data are yet available to determine the column density using x-ray spectroscopy. the initial flux in the 2.5 s image was 3.09e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 179 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.639. burst advocate for this burst is s. b. cenko (brad.cenko at nasa.gov). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 220930a: swift detection of a burst |
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