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the distribution of jet angles for short gamma-ray bursts (sgrbs) is critical to constrain because it directly affects the true energy scale and event rate. the event rate is of particular interest in the gravitational wave era. our current knowledge of the jet angle distribution comes almost exclusively from x-ray observations at >1 day after the burst. here, we propose for chandra too observations to monitor an sgrb afterglow and constrain its collimation, either from the detection of a jet break, or the non-detection of a break to place a lower limit of >5-25 deg. a precise calculation of the jet angle also requires broad-band afterglow observations, which will be leveraged to provide the tightest constraints on the jet angle. | the late-time x-ray behavior of short gamma-ray bursts: implications for energetics and rates |
long-duration grbs are the most luminous sources of electromagnetic radiation known in the universe. their initial prompt flashes of mev gamma rays are followed by longer-lasting afterglow emission from radio waves to gev gamma rays. emission at tev energies had been theoretically predicted, but never confirmed by observations. here we report the detection of a huge signal from grb 190114c in the tev energy range by the magic imaging atmospheric cherenkov telescopes. starting one minute after the onset of the burst, gamma rays in the energy range 0.2 -1 tev were observed at more than 50 sigma level. this allowed us to study the spectral and temporal development of the grb, revealing a new emission component in the afterglow with a power comparable to that of the synchrotron component. we found a second peak in the spectral energy distribution of the grb at an energy of few hundred gevs. our modeling, based on the data from the two dozen space- and ground-based instruments that followed grb 190114c at multiple wavelengths, supports the explanation that the second peak is due to the inverse compton radiation mechanism. the two-peaked structure of the spectral energy distribution allows us to constrain some of the key physical parameters of the grb as the bulk lorentz factor, minimal electron energy, the ratio of the radiation to magnetic field density. recently also the h.e.s.s. imaging atmospheric cherenkov telescope reported on a 5 sigma gamma-ray signal from the grb 180720b, measured in the afterglow phase, 10 hours after the onset of the explosion. these observations prove that the grbs are more powerful than assumed until recently. because the observed grbs did not show peculiar properties, we believe that from now on detection of gamma-ray signal from grb afterglows at very high energies will become one of the standard observations. | major change in understanding of grbs at tev |
report: the 60cm bootes-3/ya robotic telescope at niwa lauder in otago (new zealand) automatically responded to the swift grb 190604b (page et al. gcnc 24742) only 35 s after the burst). at the position of the swift/xrt enhanced x-ray position (evans et al. gcnc 24746), no optical afterglow is detected down to r = 15.5 (for the 1-s image gathered at 14:57:50 ut) or down to 19.8 mag (for the co-added 9x10s unfiltered images at mid-time 15:05:56 ut, i.e. 8.7 min after trigger). we thank the staff at niwa for its excellent support. | grb 190604b: bootes-3 early optical limits |
at 10:47:02 ut, the swift burst alert telescope (bat) triggered and located grb 190613b (trigger=908329). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 305.422, -4.664 which is ra(j2000) = 20h 21m 41s dec(j2000) = -04d 39' 49" 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 ~2500 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 10:48:39.5 ut, 97.5 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 305.4294, -4.6461 which is equivalent to: ra(j2000) = 20h 21m 43.06s dec(j2000) = -04d 38' 46.0" with an uncertainty of 4.8 arcseconds (radius, 90% containment). this location is 69 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 4.90e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 105 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 20:21:43.65 = 305.43189 dec(j2000) = -04:38:47.9 = -4.64665 with a 90%-confidence error radius of about 0.62 arc sec. this position is 9.2 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.76 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.07. 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 190613b: swift detection of a burst with an optical counterpart |
at 18:43:54 ut, the swift burst alert telescope (bat) triggered and located grb 191031c (trigger=932595). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 115.862, -62.335 which is ra(j2000) = 07h 43m 27s dec(j2000) = -62d 20' 04" 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 80 sec. the peak count rate was ~2400 counts/sec (15-350 kev), at ~4 sec after the trigger. the xrt began observing the field at 18:45:16.2 ut, 81.3 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 115.8682, -62.3247 which is equivalent to: ra(j2000) = 07h 43m 28.37s dec(j2000) = -62d 19' 28.9" with an uncertainty of 5.0 arcseconds (radius, 90% containment). this location is 38 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 2.60e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 90 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 0.17. burst advocate for this burst is e. ambrosi (elena.ambrosi 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 191031c: swift detection of a burst |
gamma-ray bursts (grbs) are extremely high-energy events that can be observed at very high redshift. in addition to γ rays, they can emit in x-ray, optical, and sometimes radio wavelengths. here, following the approach in srinivasaragavan et al. (2020); dainotti et al. (2021b,c) and dainotti et al (2022, submitted), we consider 82 grbs from dainotti et al. (2022a) that have been observed in optical wavelengths and fitted with a broken power law (bpl). we consider the relations between the spectral and temporal indices (closure relations; crs) according to the synchrotron forward-shock model evolving in the constant-density interstellar medium (ism; k = 0) and the stellar wind environment (k = 2) in both slow- and fast-cooling regimes, where the density profile is defined as n ∝ r-k. we find the ν > max(νc, νm) regime is most favored, where νc and νm are the cooling and characteristic frequencies, respectively. finally, we test the 2d dainotti correlation between the rest-frame end time of the plateau and the luminosity at that time on grbs that fulfill the most-favored crs. when we compare the intrinsic scatter σint of those 2d correlations to the scatter presented in dainotti et al. (2020b, 2022a), we see the scatters of our correlations generally agree with the previous values within 1σ , both before and after correction for selection bias. this new information has helped us to pinpoint subsamples of grbs with features that could drive the grb emission mechanism, and eventually allow for grbs to be used as standard candles. | the closure relations in optical afterglow of gamma-ray bursts |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 211018a (arimoto et al. gcn circ. 30943), collecting 4.4 ks of photon counting (pc) mode data between t0+304.3 ks and t0+340.2 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. we notice that source 2 and source 4 are consistent with catalogued quasars at redshift z = 0.64 and z=1.09, respectively. details of these sources are given below: source 1: ra (j2000.0): 19.5986 = 01:18:23.66 dec (j2000.0): -3.6511 = -03:39:04.1 error: 6.1 arcsec (radius, 90% conf. [enhanced position]) count-rate: (2.68 [+1.16, -0.92])e-3 ct s^-1 distance: 338 arcsec from fermi/lat position. flux: (9.3 [+4.0, -3.2])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 19.5656 = 01:18:15.74 dec (j2000.0): -3.3800 = -03:22:48.2 error: 5.1 arcsec (radius, 90% conf. [enhanced position]) count-rate: (9.6 [+3.9, -3.1])e-3 ct s^-1 distance: 884 arcsec from fermi/lat position. source 3: ra (j2000.0): 19.4544 = 01:17:49.06 dec (j2000.0): -3.6662 = -03:39:58.4 error: 7.2 arcsec (radius, 90% conf.) count-rate: (3.6 [+1.4, -1.1])e-3 ct s^-1 distance: 835 arcsec from fermi/lat position. flux: (1.85 [+0.70, -0.56])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 4: ra (j2000.0): 19.5576 = 01:18:13.83 dec (j2000.0): -3.7295 = -03:43:46.2 error: 3.2 arcsec (radius, 90% conf. [enhanced position]) count-rate: (6.6 +/- 1.6)e-3 ct s^-1 distance: 636 arcsec from fermi/lat position. flux: (1.70 +/- 0.40)e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 5: ra (j2000.0): 19.6548 = 01:18:37.16 dec (j2000.0): -3.6066 = -03:36:23.9 error: 8.0 arcsec (radius, 90% conf.) count-rate: (2.46 [+1.08, -0.85])e-3 ct s^-1 distance: 84 arcsec from fermi/lat position. flux: (5.3 [+2.3, -1.8])e-14 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/00021463. this circular is an official product of the swift-xrt team. | grb 211018a: swift-xrt observations |
we observed the field of grb 210402a (page et al., gcn 29743) using the nordic optical telescope (not) equipped with the alfosc camera. observations started at 00:19:22 ut on 2021-04-03, i.e., 2.23 hr after the burst, and we obtained 3x300 s and 5x200 s frames in the sdss r- and z- filters, respectively. preliminary analysis reveals that no optical transient is detected in our stacked images within or at the edge of the current xrt error circle (3.5 arcsec; page et al., gcn 29743), down to limiting magnitudes of r ~ 24.6 and z ~ 23.2, calibrated with nearby panstarrs stars. compared with the bright x-ray afterglow and no much x-ray column density excess, it may indicate that the burst is a high-redshift one. nir follow-ups are strongly encouraged. | grb 210402a: not optical upper limits |
at 18:16:28 ut, the swift burst alert telescope (bat) triggered and located grb 220711b (trigger=1115766). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 261.993, +24.669 which is ra(j2000) = 17h 27m 58s dec(j2000) = +24d 40' 10" 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 100 sec. the peak count rate was ~2000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 18:18:12.3 ut, 103.7 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 262.02020, 24.67997 which is equivalent to: ra(j2000) = 17h 28m 04.85s dec(j2000) = +24d 40' 47.9" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 97 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 (7.40 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 2 (+2.26/-2.02) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 113 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 0.067. 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 220711b: swift detection of a burst |
at 21:50:37 ut, the swift burst alert telescope (bat) triggered and located grb 200925b (trigger=997453). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 246.851, +78.394 which is ra(j2000) = 16h 27m 24s dec(j2000) = +78d 23' 39" 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 40 sec. the peak count rate was ~2000 counts/sec (15-350 kev), at ~5 sec after the trigger. the xrt began observing the field at 21:51:55.3 ut, 78.4 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 246.78990, 78.39033 which is equivalent to: ra(j2000) = 16h 27m 09.58s dec(j2000) = +78d 23' 25.2" with an uncertainty of 3.9 arcseconds (radius, 90% containment). this location is 46 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 4.59 x 10^20 cm^-2 (willingale et al. 2013). 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 0.04. 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 200925b: swift detection of a burst |
at 00:56:35 ut, the swift burst alert telescope (bat) triggered and located grb 200529a (trigger=974942). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 238.751, -11.057 which is ra(j2000) = 15h 55m 00s dec(j2000) = -11d 03' 25" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a weak pulse with a duration of about 30 sec. the peak count rate was ~1700 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 01:00:08.7 ut, 212.9 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 238.76571, -11.07215 which is equivalent to: ra(j2000) = 15h 55m 03.77s dec(j2000) = -11d 04' 19.7" with an uncertainty of 5.2 arcseconds (radius, 90% containment). this location is 75 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. no spectrum from the promptly downlinked event data is yet available to determine the column density. uvot took a finding chart exposure of 144 seconds with the white filter starting 216 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 56% 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 0.29. burst advocate for this burst is v. d'elia (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 200529a: swift detection of a burst |
long gamma-ray bursts (grbs) are among the most energetic explosions in the universe, and are commonly accepted to come from the core collapse of massive stars. these explosive events produce broadband (x-ray to radio) synchrotron emission, known as the "afterglow", which can be modeled to determine burst properties such as burst energy, circumburst density, and jet opening angle. however, a subset of these long grbs encounter significant amounts of dust obscuration along the line of sight, leading to a suppressed optical afterglow that is often faint or undetected ("dark" grb). radio detections of these dark grbs can break modeling degeneracies caused by the lack of optical emission, constraining the low frequency end of the synchrotron spectrum while the x-ray afterglow as observed by satellites such as swift constrain the high frequency end. i will present a sample of dark grbs, revealed by bright radio detections, whose afterglows and host galaxies i modeled in order to determine burst, environmental, and global properties. i compare the dark grb population to the unobscured long grb population to determine what, if anything, sets dark grbs apart from the unobscured long grb population, as well as determine the location of the dust along the line of sight of the grb. i conclude with placing constraints on obscured star formation within the host galaxies of long grbs, and make predictions for the radio detectability of long grb hosts with future radio observatories. | what grbs do in the shadows: a radio bright, dust obscured population of long grbs |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 200613a (ohno et al. gcn circ. 27931), collecting 4.9 ks of photon counting (pc) mode data between t0+43.6 ks and t0+67.6 ks. seven uncatalogued x-ray sources are detected, of which one ("source 2") is above the rass limit, and is therefore likely the grb afterglow. using 4079 s of pc mode data and 4 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 = 153.04199, +45.75408 which is equivalent to: ra (j2000): 10h 12m 10.08s dec(j2000): +45d 45' 14.7" with an uncertainty of 1.4 arcsec (radius, 90% confidence). this position is 5.8 arcmin from the fermi/lat position. the light curve can be modelled with a power-law decay with a decay index of alpha=1.6 (+/-0.5). a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 1.89 (+0.14, -0.13). the best-fitting absorption column is 2.3 (+/-0.5) x 10^21 cm^-2, in excess of the galactic value of 8.4 x 10^19 cm^-2 (willingale et al. 2013). the counts to observed (unabsorbed) 0.3-10 kev flux conversion factor deduced from this spectrum is 3.5 x 10^-11 (4.7 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 2.3 (+/-0.5) x 10^21 cm^-2 galactic foreground: 8.4 x 10^19 cm^-2 excess significance: 7.5 sigma photon index: 1.89 (+0.14, -0.13) the results of the xrt-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021003. the results of the full analysis of the xrt observations are available at https://www.swift.ac.uk/too_grbs/00021003. this circular is an official product of the swift-xrt team. | grb 200613a: swift-xrt afterglow detection |
we observed grb 211024a which was triggered by fermi gbm (fermi gbm team, gcn 30962), and further, follow up observations were carried out by swift/bat-guano (a. tohuvavohu et al., gcn 31006)), 0.7m growth-india telescope (git, kumar et al,. (gcn 31014)), using 1.3m devasthal fast optical telescope (dfot) located at devasthal observatory of aryabhatta research institute of observational sciences (aries), india. our observation was carried out in two epochs. the first epoch observation was started on 2021-10-26 at 16:22:24, i.e., ~2.62 days post-fermi trigger whereas the second epoch observation was started on 2021-10-27 at 17:43:00, i.e., ~3.68 days the fermi trigger. multiple frames in the r filter were taken in both epochs. in the first epoch, we started observing the location mentioned in swift/bat-guano a. tohuvavohu et al., (gcn 31006). but we found no uncatalogued source within the error circle of ~ 6 arcmin up to 22.73 mag. in the second epoch, we continued our observation for the 4th x-ray source given by swift-xrt too observations (m. perri et al. gcn 31013) which were assumed to be the afterglow of fermi gbm grb 211024a (gcn 30962), a. tohuvavohu et al., (gcn #31006), with 0.7m growth-india telescope (git, kumar, et al,. (gcn 31014)). we detected one source at r.a.= 1:52:46.98 , dec.= -7:00:27.30 which is coincident with an x-ray source (#4) by swift-xrt too observations (m. perri et al. gcn 31013. however, the source is not variable during our observation period. hence this is not the optical counterpart of grb 211024a. we quote an upper limit of 22.54 mag. these magnitudes are not corrected for the galactic extinction in the direction of the burst. the standard stars from the usno-b1.0 catalog was used to get the calibrated magnitude. this circular may be cited. | grb 211024a: 1.3m dfot observations |
swift-xrt has performed follow-up observations of the hawc-detected burst grb 200709b 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 1.4 ks. the data were collected between t0+5.1 ks and t0+16.9 ks, and are entirely in photon counting (pc) mode. two 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): 252.0755 = 16:48:18.12 dec (j2000.0): +15.0921 = +15:05:31.6 error: 5.8 arcsec (radius, 90% conf.) count-rate: 0.0165 [+0.0067, -0.0053] ct s^-1 distance: 1121 arcsec from hawc position. source 3: ra (j2000.0): 252.3306 = 16:49:19.35 dec (j2000.0): +15.4197 = +15:25:11.0 error: 6.2 arcsec (radius, 90% conf.) count-rate: (7.3 [+4.4, -3.2])e-3 ct s^-1 distance: 791 arcsec from hawc position. 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_grb00091. this circular is an official product of the swift-xrt team. | grb 200709b: swift-xrt observations |
at 03:51:12 ut, the swift burst alert telescope (bat) triggered and located grb 230618a (trigger=1175438). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 196.588, +3.306 which is ra(j2000) = 13h 06m 21s dec(j2000) = +03d 18' 20" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). due to a telemetry outage caused by a recent storm in guam, no further bat data will be available until a ground station pass. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 196.60313, 3.30257 which is equivalent to: ra(j2000) = 13h 06m 24.75s dec(j2000) = +03d 18' 09.3" with an uncertainty of 5.8 arcseconds (radius, 90% containment). this position may be improved as more data are received; the latest position is available at https://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 6.46e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of nominal 150.000 seconds with the white filter starting 137 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 0.025. 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 230618a: swift detection of a burst |
swift-xrt has performed follow-up observations of the integral-detected burst grb 210406a (mereghetti et al. gcn circ. 29767), collecting 5.1 ks of photon counting (pc) mode data between t0+169.5 and t0+244.5 ks. one uncatalogued x-ray source has been detected consistent with being within 148 arcsec of the integral 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 3: ra (j2000.0): 132.4988 = 08:49:59.72 dec (j2000.0): +76.5289 = +76:31:44.0 error: 6.4 arcsec (radius, 90% conf.) count-rate: (1.28 [+0.75, -0.56])e-3 ct s^-1 distance: 35 arcsec from integral position. flux: (1.46 [+0.86, -0.64])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) an uncatalogued source was also detected, however this was too far from the grb position to be the afterglow. no x-ray source is detected at the position of the optical afterglow candidate reported by belkin et al. (gcn circ. 29775) down to a 3sigma upper limit of 1.4e-3 ct s^-1. 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/00021427. this circular is an official product of the swift-xrt team. | grb 210406a: swift-xrt observations |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 201214b, collecting 5.8 ks of photon counting (pc) mode data between t0+27.2 ks and t0+51.1 ks. eight 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): 187.8292 = 12:31:19.02 dec (j2000.0): +9.0458 = +09:02:44.8 error: 4.9 arcsec (radius, 90% conf.) count-rate: (2.47 [+1.03, -0.83])e-3 ct s^-1 distance: 720 arcsec from swift/bat position. flux: (4.9 [+2.1, -1.6])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 187.9923 = 12:31:58.15 dec (j2000.0): +9.0742 = +09:04:26.9 error: 4.6 arcsec (radius, 90% conf.) count-rate: (2.50 [+0.94, -0.77])e-3 ct s^-1 distance: 175 arcsec from swift/bat position. flux: (8.2 [+3.1, -2.5])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 3: ra (j2000.0): 187.8467 = 12:31:23.21 dec (j2000.0): +9.1051 = +09:06:18.5 error: 4.6 arcsec (radius, 90% conf.) count-rate: (1.57 [+0.86, -0.65])e-3 ct s^-1 distance: 693 arcsec from swift/bat position. source 4: ra (j2000.0): 188.1338 = 12:32:32.10 dec (j2000.0): +9.1148 = +09:06:53.1 error: 6.0 arcsec (radius, 90% conf.) count-rate: (1.89 [+0.85, -0.67])e-3 ct s^-1 distance: 440 arcsec from swift/bat position. flux: (5.9 [+2.6, -2.1])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 5: ra (j2000.0): 188.1013 = 12:32:24.32 dec (j2000.0): +9.1072 = +09:06:26.1 error: 6.1 arcsec (radius, 90% conf.) count-rate: (1.49 [+0.76, -0.59])e-3 ct s^-1 distance: 333 arcsec from swift/bat position. flux: (5.4 [+2.7, -2.1])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 6: ra (j2000.0): 188.0148 = 12:32:3.54 dec (j2000.0): +8.9310 = +08:55:51.5 error: 5.2 arcsec (radius, 90% conf.) count-rate: (2.02 [+0.86, -0.69])e-3 ct s^-1 distance: 415 arcsec from swift/bat position. source 7: ra (j2000.0): 187.9055 = 12:31:37.31 dec (j2000.0): +8.9889 = +08:59:19.9 error: 5.0 arcsec (radius, 90% conf.) count-rate: (1.93 [+0.94, -0.73])e-3 ct s^-1 distance: 493 arcsec from swift/bat position. flux: (3.7 [+1.8, -1.4])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 9: ra (j2000.0): 187.9206 = 12:31:40.95 dec (j2000.0): +9.0086 = +09:00:31.1 error: 5.3 arcsec (radius, 90% conf.) count-rate: (8.0 [+6.0, -4.2])e-4 ct s^-1 distance: 417 arcsec from swift/bat position. a catalogued source was also detected. 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/00021407. this circular is an official product of the swift-xrt team. | grb 201214b: swift-xrt observations |
gamma-ray bursts (grbs) are the most energetic events known to occur in the universe. most of what is known about them comes from the study of their lower energy afterglow, due to the difficulty in pinpointing their origin in the gamma or x-ray spectrum. of particular interest are emissions in visible light which have helped confirm the link between grbs and hypernova explosions. due to the limited field of view of most telescopes, there is a sizable time gap between a grb detection by an orbiting telescope and optical telescopes slewing onto the target. to make things more challenging, the uncertainty of localization is often greater than the field of view for most telescopes. the evryscope, however, has a 16,000 sq. deg. field of view. since its deployment at ctio in 2016, it has been operating and recording all data continuously, so we have a full record of sky events stretching back years. in this work, images taken by the evryscope at the trigger times and locations provided by the fermi gamma burst monitor (gbm) team from the fermi gamma-ray space telescope (fgst) were extracted from the database. they were then processed using the evryscope subtraction pipeline, which includes a machine-learning vetting system, to create a list of transient candidates. those candidates were sorted visually, and the most prominent ones were analyzed. most were found to be flares from m-dwarf stars. | searching for optical grb afterglows with the evryscope |
at 07:09:38 ut on 2020-07-02, the swift burst alert telescope (bat) triggered and located a burst from soft gamma repeater sgr swift j1818.0-1607 (trigger=980513). swift slewed immediately to the source. the bat on-board calculated location is ra, dec 274.471, -16.167 which is ra(j2000) = 18h 17m 53s dec(j2000) = -16d 09' 59" 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 100 ms. the peak count rate was ~3000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 07:11:03.2 ut, 84.4 seconds after the bat trigger. using promptly downlinked data we find an x-ray source with an enhanced position: ra, dec 274.5017, -16.1317 which is equivalent to: ra(j2000) = 18h 18m 00.40s dec(j2000) = -16d 07' 54.2" with an uncertainty of 3.0 arcseconds (radius, 90% containment). this location is 165 arcseconds from the bat onboard position, within the bat error circle, and consistent with the catalogued position of sgr 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. 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 87 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 large, but uncertain, extinction expected. this is the fourth time swift has triggered on sgr swift j1818.0-1607; with 5 additional burst detections that did not reach the level needed for a burst response. these detections were: 2020-02-28t22:19:32 2020-03-12t21:16:47 gcn 27373 2020-04-13t19:34:18 2020-05-06t17:36:50 gcn 27696 2020-05-16t15:03:28 gcn 27746 2020-05-17t14:29:54 2020-05-25t20:23:45 2020-06-01t16:52:09 | trigger 980513: swift detection of sgr swift j1818.0-1607 |
at 20:33:15 ut, the swift burst alert telescope (bat) triggered and located grb 200512a (trigger=971846). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 7.396, -2.199 which is ra(j2000) = 00h 29m 35s dec(j2000) = -02d 11' 54" 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 ~600 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 20:34:25.5 ut, 69.7 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 7.41520, -2.21052 which is equivalent to: ra(j2000) = 00h 29m 39.65s dec(j2000) = -02d 12' 37.9" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 80 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 2.94 x 10^20 cm^-2 (willingale et al. 2013). the initial flux in the 2.5 s image was 7.60e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 250 seconds with the u filter starting 235 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 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 expected extinction corresponding to e(b-v) of 0.03. burst advocate for this burst is k. k. simpson (kira.simpson1984 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 200512a: swift detection of a burst |
at 14:39:31 ut, the swift burst alert telescope (bat) triggered and located grb 200215a (trigger=956639). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 34.122, +12.781 which is ra(j2000) = 02h 16m 29s dec(j2000) = +12d 46' 50" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve up to t+8s showed a single-peaked structure with a duration of about 20 sec. (the light curve after t+8s is not immediately available.) the peak count rate was ~4000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 14:40:59.0 ut, 87.1 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 34.0794, 12.7704 which is equivalent to: ra(j2000) = 02h 16m 19.05s dec(j2000) = +12d 46' 13.6" with an uncertainty of 2.1 arcseconds (radius, 90% containment). this location is 154 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 (1.21 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 4.2 (+3.73/-3.12) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 90 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 0.15. burst advocate for this burst is m. g. bernardini (grazia.bernardini 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 200215a: swift detection of a burst |
the binary neutron star merger gravitational-wave event gw170817 and observations of the subsequent electromagnetic signals at different wavelengths have helped better understand the outflows that follow these mergers. in particular, the off-axis afterglow of the jetted ejecta has allowed to probe the lateral structure of such jets, especially thanks to vlbi imagery of the source. in this work, we model this afterglow including a decelerating jet with lateral structure, while synchrotron emission and synchrotron self-compton scatterings power the jet radiation. in particular, we extend our analysis to very high energies and predict the light curve in the energy range of h.e.s.s. and the cta. we finally discuss how future detections of afterglows by these observatories can help break the degeneracies in some key physical parameter measurements, and allow to probe efficiently a sub-population of fast-merging binaries. | the off-axis afterglow of gw170817: flux prediction at very high energies |
at 12:00:48 ut, the swift burst alert telescope (bat) triggered and located grb 210725b (trigger=1061554). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 192.932, +17.125 which is ra(j2000) = 12h 51m 44s dec(j2000) = +17d 07' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the immediately-available bat light curve (extending to t+8 seconds) shows a complex peak of at least 5 seconds duration. the peak count rate was ~1000 counts/sec (15-350 kev), at ~2 sec after the trigger. the xrt began observing the field at 12:02:18.8 ut, 90.9 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 192.9219, 17.1080 which is equivalent to: ra(j2000) = 12h 51m 41.26s dec(j2000) = +17d 06' 28.9" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 70 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. no spectrum from the promptly downlinked event data is yet available to determine the column density. uvot took a finding chart exposure of 250 seconds with the u filter starting 91 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 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 expected extinction corresponding to e(b-v) of 0.023. burst advocate for this burst is m. g. bernardini (grazia.bernardini 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 210725b: swift detection of a burst |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 211024a (aaron tohuvavohu et al. gcn circ. 31006), collecting 5.1 ks of photon counting (pc) mode data between t0+221.8 ks and t0+234.5 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 3: ra (j2000.0): 27.9803 = 01:51:55.28 dec (j2000.0): -6.9611 = -06:57:39.9 error: 9.0 arcsec (radius, 90% conf.) count-rate: (1.24 [+0.76, -0.56])e-3 ct s^-1 distance: 261 arcsec from swift/bat position. flux: (4.0 [+2.4, -1.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 4: ra (j2000.0): 28.1958 = 01:52:47.00 dec (j2000.0): -7.0082 = -07:00:29.4 error: 3.3 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0146 [+0.0032, -0.0029] ct s^-1 distance: 527 arcsec from swift/bat position. flux: (3.49 [+0.76, -0.70])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 5: ra (j2000.0): 27.8881 = 01:51:33.14 dec (j2000.0): -6.9512 = -06:57:04.2 error: 6.8 arcsec (radius, 90% conf.) count-rate: (1.21 [+0.83, -0.59])e-3 ct s^-1 distance: 592 arcsec from swift/bat position. source 6: ra (j2000.0): 28.0277 = 01:52:6.65 dec (j2000.0): -7.0969 = -07:05:48.8 error: 7.5 arcsec (radius, 90% conf.) count-rate: (1.60 [+0.87, -0.66])e-3 ct s^-1 distance: 454 arcsec from swift/bat position. a catalogued source was also detected. 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/00021464. this circular is an official product of the swift-xrt team. | grb 211024a: swift-xrt observations |
at 06:50:26 ut, the swift burst alert telescope (bat) triggered and located grb 230802a (trigger=1182085). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 76.221, +19.570 which is ra(j2000) = 05h 04m 53s dec(j2000) = +19d 34' 10" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a wide pulse structure with a duration of about 60 sec. the peak count rate was ~3000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 06:51:30.3 ut, 64.1 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 76.23952, 19.56147 which is equivalent to: ra(j2000) = 05h 04m 57.48s dec(j2000) = +19d 33' 41.3" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 69 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. 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 1.25e-09 erg cm^-2 s^-1 (0.2-10 kev). 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 0.614. 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 230802a: swift detection of a burst |
at 05:50:50 ut, the swift burst alert telescope (bat) triggered and located grb 230228a (trigger=1156572). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 18.403, +44.489 which is ra(j2000) = 01h 13m 37s dec(j2000) = +44d 29' 19" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single symmetrical peak structure with a duration of about 1.5 sec. the peak count rate was ~2000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 05:52:49.2 ut, 119.0 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 18.37776, 44.48321 which is equivalent to: ra(j2000) = 01h 13m 30.66s dec(j2000) = +44d 28' 59.6" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 68 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 9.72 x 10^20 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 122 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 0.085. 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 230228a: swift detection of a possibly short burst |
in order to obtain an overview of gamma-ray bursts (grbs), we need a full sample. in this paper, we collected 6289 grbs (from grb 910421 to grb 160509a) from the literature, including their prompt emission, afterglow, and host galaxy properties. we hope to use this large sample to reveal the intrinsic properties of grbs. we have listed all of the data in machine-readable tables, including the properties of the grbs, correlation coefficients and linear regression results of two arbitrary parameters, and linear regression results of any three parameters. these machine-readable tables could be used as a data reservoir for further studies on the classifications or correlations. one may find some intrinsic properties from these statistical results. with these comprehensive tables, it is possible to find relations between different parameters and to classify the grbs into different subgroups. upon completion, they may reveal the nature of grbs and may be used as tools like pseudo-redshift indicators, standard candles, etc. (5 data files). | vizier online data catalog: a comprehensive statistical study of gamma-ray bursts (wang+, 2020) |
following its installation at sutherland in late dec 2014, the saao node of the master optical transient detection network has been busy discovering new optical transient sources and following up on other transient triggers. this is the first general transient detection system to be installed at saao, allowing for the rapid detection and followup of the likes of cvs, grbs, sne and flaring blazars. up to mid-march 2015, some 40 transients have been discovered by master-saao. in addition several gamma ray burst (grb) follow-up observations were conducted with master-saao, leading to the identification of optical counterparts and the determination of the afterglow decay light curves for two of them, and upper limits for the rest. we discuss the master-saao system and future plans to automate followup observations with salt and a new 1.0 m robotic telescope at saao. | master-saao: optical transient detections and followups |
at 18:35:42 ut, the swift burst alert telescope (bat) triggered and located grb 231216a (trigger=1202749). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 39.759, +33.596 which is ra(j2000) = 02h 39m 02s dec(j2000) = +33d 35' 45" 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 70 sec. the peak count rate was ~2000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 18:37:53.1 ut, 131.1 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 39.77287, 33.57671 which is equivalent to: ra(j2000) = 02h 39m 05.49s dec(j2000) = +33d 34' 36.2" with an uncertainty of 3.9 arcseconds (radius, 90% containment). this location is 80 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 8.36 x 10^20 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 250 seconds with the u filter starting 191 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 33% of the xrt error circle. the typical 3-sigma upper limit has been about 19.2 mag. results 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 0.081. burst advocate for this burst is t. sbarrato (tullia.sbarrato 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 231216a: swift detection of a burst |
in this conference proceeding we summarise our investigation of a correlation discovered between the afterglow luminosity (measured at restframe 200 s; log l200s) and average afterglow decay rate (measured from restframe 200 s onwards; α>200s) of long duration gamma-ray burst (grb) afterglows, found in both the optical/uv and x-ray after- glows. we examine the correlation in the x-ray light curves and find that it does not depend on the presence of specific features in the x-ray light curve. we test how the optical and x-ray parameters log lo,200s, log lx,200s, αo,>200s, αx,>200s relate to each other and to parameters from the prompt emission phase. using a monte carlo simu- lation, we explore whether these relationships are consistent with predictions of a basic standard afterglow model. we conclude that most of the correlations we observe are consistent with a common underlying physical mechanism producing grbs and their afterglows regardless of their detailed temporal behaviour, but this basic model has dif- ficulty explaining correlations involving α>200s. we therefore briefly discuss alternative more complex afterglow models. | exploring the canonical behaviour of long gamma-ray bursts using an intrinsic multi-wavelength afterglow correlation |
at 22:37:26 ut, the swift burst alert telescope (bat) triggered and located grb 210222b (trigger=1034325). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 154.621, -14.898 which is ra(j2000) = 10h 18m 29s dec(j2000) = -14d 53' 52" 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 ~1250 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 22:39:02.1 ut, 95.9 seconds after the bat trigger. using promptly downlinked data we find an x-ray source with an enhanced position: ra, dec 154.6062, -14.9316 which is equivalent to: ra(j2000) = 10h 18m 25.50s dec(j2000) = -14d 55' 53.7" with an uncertainty of 2.1 arcseconds (radius, 90% containment). this location is 131 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 (8.87 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3 (+1.87/-1.66) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of nominal 150.000 seconds with the white filter starting 100 seconds after the bat trigger. there is a candidate afterglow in the list of sources generated on-board at ra(j2000) = 10:18:25.45 = 154.60606 dec(j2000) = -14:55:55.7 = -14.93215 with a 90%-confidence error radius of about 1.10 arc sec. this position is 2.0 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.65. no correction has been made for the expected extinction corresponding to e(b-v) of 0.101. this source lies within the current (sector 35) field-of-view of tess camera 1. we note that this source is 32 arcseconds from the known rosat all-sky x-ray survey source 1rxs j101827.6-145604. this is outside of the nominal joint error radius and so we believe that the rosat source is a coincidental alignment unrelated to the new grb and its optical counterpart. | grb 210222b: swift detection of a burst with an optical counterpart |
we present a method to estimate the jet opening angles of long gamma-ray bursts (grbs) using the prompt gamma-ray energetics and a correlation between the time-integrated peak energy of the grb prompt spectrum and the collimation-corrected energy in gamma rays. the derived jet opening angles using this method match well with the corresponding inferred jet opening angles obtained when a break in the afterglow is observed. furthermore, using a model of the predicted long grb redshift probability distribution observable by the fermi gamma-ray burst monitor (gbm), we estimate the probability distributions for the jet opening angle and rest-frame energetics for a large sample of gbm grbs for which the redshifts have not been observed. previous studies have only used a handful of grbs to estimate these properties due to the paucity of observed afterglow jet breaks, spectroscopic redshifts, and comprehensive prompt gamma-ray observations, and we expand the number of grbs that can be used in this analysis by more than an order of magnitude. we also present an inferred distribution of jet breaks which indicates that a large fraction of jet breaks are not observable with current instrumentation and observing strategies. a.g. is funded by the nasa postdoctoral program through usra. | estimating long grb jet opening angles and rest-frame energetics |
we performed further follow-up of the short grb 230217a (moss et al. gcn 33339, svinkin et al. gcn 33349, veres et al. gcn 33353) using the gmos instrument at gemini-south. observations were carried out in the i-band and began at 08:55:27 on 2023-02-21, corresponding to ~3.5 d after the grb trigger. following recent xrt observations, x-ray source 3 has been confirmed to fade with >3-sigma significance, and thus is likely the grb afterglow (capalbi et al. gcn 33365). by performing image subtraction between the two gemini observations (see also o'connor et al. gcn 33356, troja et al. gcn 33360) we find no sign of variability and place a limit of i>23 ab mag over the entire xrt error circle. at the position of the radio source #3 (schroeder et al. gcn 33358), we set an upper limit of i>24.3 ab mag at 3.5 d post-burst. this value is not corrected for galactic extinction. we thank the staff of the gemini observatory for executing these observations. | grb 230217a: continued gemini observations |
at 02:56:57 ut, the swift burst alert telescope (bat) triggered and located grb 230204a (trigger=1152509). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 238.164d, -50.858d which is ra(j2000) = 15h 52m 39s dec(j2000) = -50d 51' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). due to a telemetry gap, the bat lightcurve before t+8s is not immediately available, and no obvious variation is visible in the remainder of the lightcurve, as is typical for an image trigger. the xrt began observing the field at 02:59:24.1 ut, 146.8 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 238.1950, -50.9167 which is equivalent to: ra(j2000) = 15h 52m 46.80s dec(j2000) = -50d 55' 00.1" with an uncertainty of 5.0 arcseconds (radius, 90% containment). the initial flux in the 2.5 s image was 2.77e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 156 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 large, but uncertain, extinction expected. we note that this source is near the galactic plane (lat=2.38 deg) and was detected as a 64 s image trigger, which raises the possibility that this is a galactic transient. we would name this source swift j1552.8-5055 if it is not a grb. further analysis of the nature of this source will require the full downlinked dataset. 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 230204a: swift detection of a possible burst (or possible transient swift j1552.8-5055) |
"we observed the short grb 230217a (moss et al., gcn 33339; casentini et al., gcn 33343; torii et al., gcn 33342; svinkin et al., gcn 33349) with the karl g. jansky very large array (vla) under program 23a-296 (pi: schroeder) beginning on 2023 february 18.67 ut (0.76 days post-burst) at a mean frequency of 6 ghz. the vla has a primary beam of ~7 arcmin at 6 ghz, covering the entirety of the swift/bat position (moss et al., gcn 33339). we searched for radio sources near the two x-ray sources coincident with the swift/bat localization found by swift/xrt (source 3 and source 5, capalbi et. al gcn 33348), though neither x-ray source has been definitively determined the x-ray afterglow. we detect radio sources coincident with both xrt sources. our preliminary results are as follows: source 3: flux of ~65 microjy (~9 sigma) at the position: ra(j2000) = 18:43:04.948 dec(j2000) = -28:50:16.60 with an uncertainty of ~0.3" in each coordinate. source 5: flux of ~20 microjy (~3 sigma) at the position: ra(j2000) = 18:43:06.762 dec(j2000) = -28:46:48.06 with an uncertainty of ~0.6" in each coordinate. we thank the vla staff for quickly approving and executing these observations." | grb 230217a: 6 ghz vla observations |
swift-xrt has performed follow-up observations of the maxi-detected burst grb 230204b (serino et al. gcn circ. 33265). a possible optical counterpart was reported by git (swain et al. gcn circ. 33269). swift-xrt observations consist of 4.2 ks of photon counting (pc) mode data between t0+80.5 ks and t0+97.9 ks. one uncatalogued x-ray source has been detected consistent with the git position. the source is below the rass limit but does not show definitive signs of fading. this is most likely the afterglow, given also the reported redshift of z=2.14 (saccardi et al. gcn circ. 33281) but further observations are required to assess for fading. details of this source are given below: source 3: ra (j2000.0): 197.6441 = 13:10:34.58 dec (j2000.0): -21.7164 = -21:42:58.9 error: 7.4 arcsec (radius, 90% conf.) count-rate: (5.6 +/- 1.5)e-3 ct s^-1 distance: 8 arcsec from maxi position. flux: (3.8 +/- 1.0)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/00021535. this circular is an official product of the swift-xrt team. | grb 230204b: swift-xrt afterglow detection |
at 03:03:19 ut, the swift burst alert telescope (bat) triggered and located grb 231117a (trigger=1197027). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 332.409, +13.514 which is ra(j2000) = 22h 09m 38s dec(j2000) = +13d 30' 49" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single bright peak structure with a duration of about 1.5 sec. the peak count rate was ~80,000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 03:05:01.5 ut, 101.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 332.39146, 13.52328 which is equivalent to: ra(j2000) = 22h 09m 33.95s dec(j2000) = +13d 31' 23.8" with an uncertainty of 4.3 arcseconds (radius, 90% containment). this location is 69 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. uvot took a finding chart exposure of 150 seconds with the white filter starting 105 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image processing failed because of no aspect solution. results 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 0.071. 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 231117a: swift detection of a bright short burst |
no abstract available. | grandma and hxmt observations of grb 221009a - the standard-luminosity afterglow of a hyper-luminous gamma-ray burst |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 230707a, collecting 4.7 ks of photon counting (pc) mode data between t0+32.7 ks and t0+51.0 ks. no x-ray sources have been detected consistent with being within 197 arcsec of the swift/bat-guano 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 9.4e-14 to 1.3e-13 erg cm^-2 s^-1 (assuming a typical grb spectrum). three 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/00021587. this circular is an official product of the swift-xrt team. | grb 230707a: swift-xrt observations |
at 01:17:52 ut, the swift burst alert telescope (bat) triggered and located grb 201006a (trigger=998907). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 61.880, +65.150 which is ra(j2000) = 04h 07m 31s dec(j2000) = +65d 08' 59" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows a single spike structure with a duration of about 5 sec. the peak count rate was ~2500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 01:19:15.9 ut, 83.9 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 61.8932, 65.1650 which is equivalent to: ra(j2000) = 04h 07m 34.36s dec(j2000) = +65d 09' 54.0" with an uncertainty of 2.6 arcseconds (radius, 90% containment). this location is 57 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 4.50 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 87 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 1.27. 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 201006a: swift detection of a burst |
at 22:37:34 ut, the swift burst alert telescope (bat) triggered and located grb 201026a (trigger=1002103). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 196.664, +83.761 which is ra(j2000) = 13h 06m 39s dec(j2000) = +83d 45' 38" 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 30 sec. the peak count rate was ~1700counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 22:38:53.0 ut, 78.8 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 196.7408, 83.7849 which is equivalent to: ra(j2000) = 13h 06m 57.79s dec(j2000) = +83d 47' 05.6" with an uncertainty of 4.8 arcseconds (radius, 90% containment). this location is 91 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 7.01e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 87 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 0.18. 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 201026a: swift detection of a burst |
in this work we present the detection capability of the mirax (monitor e imageador de raios-x) experiment for gamma-ray bursts (grbs). mirax is an x-ray astronomy mission designed to perform a wide band hard x-ray (10-200 kev) survey of the sky, especially in the galactic plane. with a total detection area of 169 cm2, large field of view (fov, 20 ° × 20 °), angular resolution of 1°45‧ and good spectral and time resolution (∼8% at 60 kev, 10 μs), mirax will be optimized for the detection and study of transient sources, such as accreting neutron stars (ns), black holes (bh), active galactic nuclei (agns), and both short and long grbs. this is especially important because mirax is expected to operate in an epoch when probably no other hard x-ray wide-field imager will be active. we have performed detailed simulations of mirax grb observations using the geant4 package, including the background spectrum and images of grb sources in order to provide accurate predictions of the sensitivity for the expected grb rate to be observed. mirax will be capable of detecting ∼44 grbs per year up to redshifts of ∼4.5. the mirax mission will be able to contribute significantly to grb science by detecting a large number of grbs per year with wide band spectral response. the observations will contribute mainly to the part of grb spectra where a thermal emission is predicted by the fireball model. we also discuss the possibility of detecting grb afterglows in the x-ray band with mirax. | mirax sensitivity for gamma ray bursts |
swift-xrt has performed follow-up observations of the first optical afterglow candidate observed by meerlicht (de wet et al. gcn circ. 32460) of the fermi/gbm detected burst grb 220810a (fermi gbm team, gcn 32455), collecting 2.0 ks of photon counting (pc) mode data between t0+202.1 ks and t0+208.1 ks. no x-ray sources have been detected at the meerlicht optical afterglow candidate position. the 3-sigma upper limit in the field is 0.006 ct s^-1, corresponding to a 0.3-10 kev observed flux of 2.2e-13 erg cm^-2 s^-1 (assuming a typical grb spectrum). this circular is an official product of the swift-xrt team. | grb 220810a: further swift-xrt observations |
at 02:46:52 ut, the swift burst alert telescope (bat) triggered and located grb 210930a (trigger=1075565). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 197.435, +48.623 which is ra(j2000) = 13h 09m 44s dec(j2000) = +48d 37' 22" 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 15 sec. the peak count rate was ~800 counts/sec (15-350 kev), at ~8 sec after the trigger. the xrt began observing the field at 02:49:12.3 ut, 140.1 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 197.40185, 48.62853 which is equivalent to: ra(j2000) = 13h 09m 36.44s dec(j2000) = +48d 37' 42.7" with an uncertainty of 3.8 arcseconds (radius, 90% containment). this location is 81 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 (9.55 x 10^19 cm^-2, willingale et al. 2013), with an excess column of 6.4 (+3.87/-3.20) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 143 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 0.010. 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 210930a: swift detection of a burst |
at 00:16:21 ut, the swift burst alert telescope (bat) triggered and located grb 200425a (trigger=967774). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 85.241, -13.459 which is ra(j2000) = 05h 40m 58s dec(j2000) = -13d 27' 31" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the immediately-available bat light curve data only extends to t+8s, at which time the grb was still active with a multi-peaked structure. the peak count rate up to that time was ~1000 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 00:17:52.2 ut, 90.5 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 85.2198, -13.4352 which is equivalent to: ra(j2000) = 05h 40m 52.76s dec(j2000) = -13d 26' 06.8" with an uncertainty of 2.9 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 1.59 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 93 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 0.16. burst advocate for this burst is m. g. bernardini (grazia.bernardini 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 200425a: swift detection of a burst |
at 06:27:58 ut, the swift burst alert telescope (bat) triggered and located grb 201128a (trigger=1009679). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 223.136, +26.678 which is ra(j2000) = 14h 52m 33s dec(j2000) = +26d 40' 41" 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 ~600 counts/sec (15-350 kev), at ~2 sec after the trigger. the xrt began observing the field at 06:30:04.8 ut, 126.6 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 223.1083, 26.6844 which is equivalent to: ra(j2000) = 14h 52m 26.00s dec(j2000) = +26d 41' 03.8" with an uncertainty of 2.6 arcseconds (radius, 90% containment). this location is 92 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 3.53 x 10^20 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 130 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 0.03. 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 201128a: swift detection of a burst |
on september 28th, 2021, fermi-lat detected high-energy emission from grb 210928a, which was also detected by fermi gbm (trigger 654487236 / 210928084). this source has previously been reported as the fermi-lat transient j1623-1752 (rani et al., atel #14939) and swift x-ray transient j162315.0-175233 (page et al.; atel #14945). further analysis shows that the lat source is consistent with being a grb, making the swift transient the afterglow candidate. the best lat on-ground location is found to be ra, dec = 245.88, -17.91 (degrees, j2000) with an error radius of 0.15 deg (90% containment, statistical error only). this location is consistent with the swift x-ray transient. the position was 16 deg from the lat boresight at the time of the gbm trigger: t0 = 02:00:31 ut. the data from the fermi-lat show a significant increase in the event rate after the trigger that is spatially correlated with the gbm emission with high significance. the photon flux above 100 mev in the time interval 0-1000 s after the trigger is 8.4 (-/+ 1.5) e-06 ph/cm2/s. the estimated photon index above 100 mev is -2.2 (-/+ 0.2). the highest-energy photon is a 6 gev event which is observed ~50 s after the trigger. the fermi-lat point of contact for this burst is magnus axelsson (magaxe@kth.se). the fermi-lat is a pair conversion telescope designed to cover the energy band from 20 mev to greater than 300 gev. it is the product of an international collaboration between nasa and doe in the u.s. and many scientific institutions across france, italy, japan and sweden. | grb 210928a: fermi-lat detection |
we observed the field of grb 210704a (berretta et al., gcn circ. 30375; d'ai et al., gcn circ. 30379; malacaria & meegan, gcn circ. 30380; kim et al., gcn circ. 30384) with the osiris instrument on the 10.4 meter gtc telescope. we observed at two epochs. the first epoch was at 2.10 days after burst and the second at 5.10 days after burst. at both epochs, we detect a source at the position of the candidate optical afterglow (kim et al., gcn circ. 30384) at a magnitude consistent with the tng observations of r~23.3 at 4.1 days (d'avanzo et al., gcn circ. 30432). we also resolve a second fainter (r~24.5 ab mag) source (s2) located 0.7 arcsec e and 2.4 arcsec s of the ot position. our observations indicate only a marginal fading of about 0.2 magnitudes in the r-band between our two epochs, which is unusually shallow for a grb afterglow or for a kilonova. archival pre-explosion images of the field reveal the presence of an underlying faint source (s1), which might be the host galaxy. based on a deep exposure obtained in 2012 with the megaprime/megacam, we estimate a magnitude of r~25.3 +/- 0.2 ab mag for s1. the source s2 is also detected in archival images at a magnitude consistent with our gtc observations. assuming no intrinsic variability, s1 would only partially contribute to the observed optical light (~25%) and this by itself is not sufficient to explain the slow fading of the optical emission. given the ambiguous classification of the gamma-ray emission, whose duration lies at the intersection between short and long grbs, we cannot exclude that the observed flattening marks the onset of an associated supernova. further observations to monitor the evolution of this source are encouraged. we thank david garcia and antonio cabrera for assistance with these observations. | grb 210704a: osiris/gtc observations and archival detection of the possible host galaxy |
we observed the location of the short grb 211106a; 37, with the hubble space telescope starting on 2021 november 25.; acs/f814w, using; orbits each, wfc3/f110w for 2; program 16303, as part of; x-ray afterglow detected with chandra, . within the 0. 8-arcsec error circle of the; single source in both filters at, we detect a; 7, ra = 225420. 54 dec =-531350. 6 with an uncertainty of about 0. 05 arcsec. preliminary photometry indicates ab magnitudes of m~ 25. "f814w"; slightly extended, m~ 25. 6. we note that the source may be "f110w"; is the afterglow, in the f110w image. the origin of the optical/nir source is unclear at the present. if it; observed in the x-rays, then a similar decline rate as; vlt/fors2 observations, would indicate an expected optical magnitude of~23. 7 at the time of the; kilonova, over 2 mag brighter than the limit of r~26 mag listed in gcnc #31070. if the source is a; z=0. 097 identified in vlt data, the event is associated with the galaxy at; mag, then it is about 2. 5; kilonova associated with gw170817, more luminous in j-band than the; significantly bluer, moreover; mag. finally, with m-m~ 0 "f814w f110w"; grb 211106a, it is possible that the optical/nir source is the actual host galaxy of; shed light on the nature of the source., most likely placing the burst at a higher redshift than z=0. 097. additional hst observations are planned to | grb 211106a: hst observations |
the full-frame images produced by the transiting exoplanet survey satellite (tess) are invaluable tools to detect periodic and transient astrophysical events, such as variable stars, supernovae, tidal disruption events, and gamma-ray burst afterglows. our pixel-level method separates the time-series ffis into smaller groups and then calculates the per-pixel variance over the duration of each group. these variance maps are then combined across adjacent groups to produce a "variability" image in which systematics, like those caused by scattered light and differential velocity aberration, are mitigated. all point sources in the variability image are extracted and classified using a convolutional neural network (cnn) that has been trained on known transients from tess's prime mission. our cnn has 90% accuracy on test data, which will increase as newly-identified transients are added to the training set. sources with the highest probabilities (assigned through classification) are filtered by matching with catalogs like simbad and tns, and photometry is done on the set of filtered sources. the generated light curves are then analyzed using a variety of statistical techniques to prioritize those that are most important for follow-up. we are thus able to filter the tens to hundreds of thousands of point sources in each variability image to a manageable level (100s per sector) that can then be visually inspected prior to follow-up. our technique has also shed light on poorly-characterized detector systematics that must be mitigated to increase our pipeline's snr. future work will involve exploiting the novel 10-minute ffis to evaluate transient light curves in finer detail. additionally, we hope to identify tess-band counterparts to high-energy transient events, such as compact object mergers and frbs, that have large error ellipses. | leveraging machine learning to detect transients in tess ffis |
we have analysed 5.7 ks of photon counting (pc) mode xrt data for the swift-bat-detected burst grb 220730a (dichiara et al. gcn circ. 32431), collected between t0+3.8 ks and t0+51.6 ks. four 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 1: ra (j2000.0): 224.9153 = 14:59:39.66 dec (j2000.0): -69.5540 = -69:33:14.4 error: 6.4 arcsec (radius, 90% conf.) count-rate: (1.27 [+0.69, -0.53])e-3 ct s^-1 distance: 244 arcsec from swift-bat position. flux: (4.0 [+2.2, -1.7])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 5: ra (j2000.0): 225.0143 = 15:00:3.43 dec (j2000.0): -69.4959 = -69:29:45.4 error: 6.6 arcsec (radius, 90% conf.) count-rate: (1.90 [+1.02, -0.77])e-3 ct s^-1 distance: 9 arcsec from swift-bat position. flux: (4.0 [+2.2, -1.6])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 7: ra (j2000.0): 225.0749 = 15:00:17.98 dec (j2000.0): -69.4908 = -69:29:26.9 error: 7.3 arcsec (radius, 90% conf.) count-rate: (1.68 [+0.79, -0.62])e-3 ct s^-1 distance: 71 arcsec from swift-bat position. flux: (1.12 [+0.53, -0.41])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 8: ra (j2000.0): 224.9654 = 14:59:51.71 dec (j2000.0): -69.5389 = -69:32:20.2 error: 7.4 arcsec (radius, 90% conf.) count-rate: (2.53 [+0.93, -0.76])e-3 ct s^-1 distance: 166 arcsec from swift-bat position. flux: (3.13 [+1.15, -0.94])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) 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 https://www.swift.ac.uk/too_grbs/01118357. this circular is an official product of the swift-xrt team. | grb 220730a: swift-xrt observations |
gamma-ray bursts (grbs) are the most explosive phenomena in the universe after the big bang. a large fraction of grb lightcurves (lcs) shows x-ray plateaus. we perform the most comprehensive analysis of all grbs (with known and unknown redshifts) with plateau emission observed by the neil gehrels swift observatory from its launch until august 2019. we fit 455 lcs showing a plateau and explore whether these lcs follow closure relations, relations between the temporal and spectral indices of the afterglow, corresponding to 2 distinct astrophysical environments and cooling regimes within the external forward shock (es) model, and find that the es model works for the majority of cases. the most favored environments are a constant density interstellar or wind medium with slow cooling. we also confirm the existence of the fundamental plane relation between the rest-frame time and luminosity at the end of the plateau emission and the peak prompt luminosity for this enlarged sample, and test this relation on groups corresponding to the astrophysical environments of our known redshift sample. the plane becomes a crucial discriminant corresponding to these environments in terms of the best fitting parameters and dispersions. most grbs for which the closure relations are fulfilled with respect to astrophysical environments have an intrinsic scatter sigma compatible within 1 sigma of that of the gold grbs, a subset of long grbs with relatively flat plateaus. we also find that grbs satisfying closure relations indicating a fast cooling regime have a lower sigma than ever previously found in literature. | on the investigation of the closure relations for gamma-ray bursts observed by swift in the post-plateau phase and the grb fundamental plane |
the discovery of the first binary neutron star merger directly associated to a short gamma-ray bursts (gw170817/grb170817a) reveal the presence of a local population of off-axis events. in our work we investigate whether similar nearby (<200 mpc) events were observed by nasa's neil gehrels swift observatory. the onset of the x-ray ray emission from these events is expected after several days from the grb discovery and is significantly fainter than the on-axis afterglow as reveled by chandra observation of grb170817a. we selected all the events not associated to any x-ray or optical counterpart, finding 4 cases possibly associated with galaxies at distance <200 mpc. although affected by low statistics, this number is higher than the one expected for chance alignments to random galaxies, and possibly suggests a physical association between these bursts and nearby galaxies. we discuss the nature of these objects, and use them to constrain the rate of local sgrbs. by comparing our inferred rates with the most recent results from the advanced ligo and virgo o3 run we derive information about the outflow collimation and its structure. | search of short grbs within 200 mpc with neil gehrels swift observatory |
on christmas day in 2010, the swift observatory detected gamma rays from a mysterious source for a whopping 28 minutes. more than a decade later, astronomers are still theorizing about the cause of this unusual gamma-ray burst.digital rendering of the aftermath of a collision between a neutron star and a red giant, which is one possible explanation for grb 101225a. [nasa/goddard space flight center]an intriguing eventgrb 101225a, dubbed the christmas burst because of its holiday debut, has inspired plenty of theories due to its unusually long-duration gamma-ray emission and its unexpectedly brief, flaring x-ray emission. the proposed causes range from long-distance (a neutron star billions of light-years away being engulfed by a red-giant companion) to local (a neutron star 10,000 light-years away snacking on a comet). further hypotheses include a collapsing ultra-low-metallicity blue supergiant star or even a never-before-seen class of astrophysical phenomena.the authors of todays article put forward a new hypothesis: what if grb 101225as unusual emission comes from something weve seen before but viewed from a different angle?x-ray and optical afterglow (ag) emission from grb 101225a (black and orange symbols, respectively) as well as two other events potentially involving off-axis jets (blue and pink symbols). the solid lines show the results of the jet model, while the dashed lines are empirical fits to the data. the x-axis indicates the time since the burst alert telescope (bat) observations began. click to enlarge. [zou et al. 2021]modeling multiwavelength emissionthe motivation for this theory, developed by le zou (guangxi university, china) and collaborators, came from observations of a more recent gamma-ray burst: grb 170817a. the gravitational-wave signal that preceded this gamma-ray burst indicated that it resulted from two neutron stars colliding, potentially leaving behind a massive newborn magnetar a neutron star with an extremely strong magnetic field with a relativistic jet. further analysis of the events multiwavelength emission suggested that the jet was viewed at an angle, potentially as much as a few tens of degrees off center.zou and coauthors explored the possibility that grb 101225a was also caused by a newly formed magnetar with a jet, and its unusual gamma-ray and x-ray signatures arise as a result of our off-axis view.to test this theory, the team modeled the emission from a relativistic jet colliding with the surrounding interstellar medium and compared their results to the observations. the authors find that the optical data are consistent with the afterglow produced by a narrow jet viewed from just a few degrees off center.a more detailed viewobserved (black) and modeled (red) x-ray flux from grb 101225a. [adapted from zou et al. 2021]the authors suggest that their model also explains the flaring behavior seen in grb 101225as x-ray emission hours after the onset of the event. if grb 101225a is caused by a magnetar, we should see semi-periodic oscillations in the x-ray flux caused by the precession of the magnetars rotation. the teams x-ray model roughly reproduces the observed flares with periods of 250 and 488 seconds, suggesting that the flaring behavior could be due to the precession of a magnetar.the teams results are still tentative, and more data could help tease out the cause of this unusual event. much like the observations of gravitational waves from grb 170817a enhanced our understanding of that event, so will gravitational-wave observations of future grb 101225a-like events. the team estimated that current gravitational-wave observatories arent sensitive enough to detect a grb 101225a-like event, but future observatories should be. as we learn more about this varied class of events, we should be able to refine our understanding and put our many theories to the test.citationgrb 101225a as orphan dipole radiation of a newborn magnetar with precession rotation in an off-axis gamma-ray burst, le zou et al 2021 apjl 921 l1. doi:10.3847/2041-8213/ac2ee4 | revisiting the "christmas burst" |
gamma-ray bursts are bright enough to be seen to 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 in the era of reionization. efforts to identify high-z grbs have been rewarded with the discoveries of several grbs at redshifts z>6.5. however, it remains the case that some good high-z candidates cannot be followed up quickly or deeply enough with ground-based ir spectroscopy, and indeed for others the ly-a 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-a 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>6.5 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>6.5 grbs leads us to request a long-term too program, spanning cycles 29 and 30; where in cycle 30 we will benefit from triggers being supplemented by those from the new svom satellite. | identifying gamma-ray bursts at very high redshifts |
gamma-ray bursts (grbs) are fascinating events due to their panchromatic nature. we study optical plateaus in grb afterglows via an extended search into archival data. we comprehensively analyze all published grbs with known redshifts and optical plateaus observed by many ground-based telescopes (e.g., subaru telescope, ratir) around the world and several space-based observatories such as the neil gehrels swift observatory. we fit 502 optical light curves (lcs), showing the existence of the plateau in 181 cases. this sample is 77% larger than the previous one (dainotti, 2021), and it is the largest compilation so far of optical plateaus. with this sample, we discover the 3d fundamental plane relation at optical wavelengths. this correlation is between the rest-frame time at the end of the plateau emission, t*opt, its optical luminosity, lopt, and the peak in the optical prompt emission, lpeak,opt, thus resembling the three-dimensional (3d) x-ray fundamental plane relation (dainotti, 2016). we correct our sample for redshift evolution and selection effects, discovering that this correlation is indeed intrinsic to grb physics. we investigate the rest-frame end time distributions in x-rays and optical (t*opt, t*x), and conclude that the plateau is achromatic only when selection biases are not considered. we also investigate if the 3d optical correlation may be a new discriminant between optical grb classes and find that there is no significant separation between the classes compared to the gold sample plane after correcting for evolution. | the optical two and three-dimensional fundamental plane correlations for more than 180 gamma-ray burst afterglows with swift/uvot, ratir, and the subaru telescope |
jets are a ubiquitous phenomena in astrophysics — spanning a remarkable range in size, velocity, and energy output. but only a handful of systems are capable of accelerating ejecta to speeds approaching that of light — the best known examples of such relativistic jets are blazars and gamma-ray bursts. here i describe recent efforts to characterize the properties of known classes of systems with relativistic jets — in particular gamma-ray bursts from both the core-collapse of massive stars as well as the merger of binary neutron stars. i will also highlight attempts to uncover new classes of relativistic ejecta, specifically evidence for such high-velocity outflows from tidal disruption events, and searches for "orphan" gamma-ray burst afterglows. along the way, i'll highlight the critical role in these efforts played by two facilities, the neil gehrels swift observatory and the zwicky transient facility. | relativistic explosions across the universe |
grb181201a was discovered by the ibis and isgri instruments on board the integral satellite on 2018 december 1 at 02:38 ut (mereghetti+ 2018gcn.23469....1m). the optical afterglow was discovered in master (lipunov+ 2010adast2010e..30l) global robotic net observations (podesta+ 2018gcn.23470....1p) 10s after the integral alert and later by the swift uv/optical telescope. we derived aperture photometry from pipeline-processed uvot images downloaded from the swift data center. four master-net observatories (master-kislovodsk, master-iac, master-saao, and master-oafa) participated in rapid-response and follow-up observations of grb 181201a, beginning on 2019 december 1 in the bvri and clear bands. we observed the afterglow of grb 181201a with the gamma-ray burst optical/near-infrared detector (grond) on the mpi/eso 2.2m telescope in la silla in chile beginning 0.91 days after the burst in g'r'i'z'jhk filters. we also observed the afterglow with the ohio state multi-object spectrograph (osmos) on the 2.4m hiltner telescope at mdm observatory on 2018 december 4, with 120s exposures each in the bvri bands. we obtained two later epochs of imaging using the templeton detector on the 1.3m mcgraw-hill telescope on the nights of 2018 december 9 and 10, obtaining 4x300s each in r' and i' bands. and we obtained liverpool telescope (lt) imaging with the infrared/optical camera (io:o) at ~2.7days, comprising 3x120s exposures in g'r'i' bands. we obtained five epochs of alma band 3 (3mm) observations of grb181201a spanning 0.88 days to 29.8d after the burst through program 2018.1.01454.t (pi: laskar). we observed the afterglow using the vla starting 2.9days after the burst through programs 18a-088 and 18b-407 (pi: laskar). we detected and tracked the flux density of the afterglow from 1.2ghz to 37ghz over multiple epochs until ~164 days after the burst. finally, we observed the afterglow using the upgraded giant meterwave radio telescope (ugmrt) through program 35_065 (pi: laskar) starting 12.5d and 13.5d after the burst in bands 4 (center frequency 550mhz) and 5 (center frequency 1450mhz), respectively. (3 data files). | vizier online data catalog: radio to uv observations of grb 181201a (laskar+, 2019) |
we observed the field of grb 210704a (kunzweiler et al., gcn circ. 30369; ursi et al., gcn circ. 30372; berretta et al., gcn circ. 30375; prasad et al., gcn 30378; malacaria et al. gcn 30380), covering the position of the x-ray afterglow reported by d'ai et al. (gcn circ. 30379) with the italian 3.6m tng telescope equipped with the optical camera dolores. a series of images were obtained with the r-sdss filter on 2021-07-05 from 21:13:11 ut to 21:39:50 ut (i.e. about 1.08 days after the burst). the optical afterglow candidate reported by kim et al. (gcn circ. 30384) is clearly detected at the following position (j2000): ra: 10:36:04.92 dec: +57:12:59.3 (+/- 0.5"). with preliminary photometry we derive the following magnitude: r = 22.13 +/- 0.13 (ab; calibrated against the sdss catalogue). as noted by kim et al. (gcn circ. 30384), this source is not visible in archival sdss and pan-starrs images. | grb 210704a: tng detection of the optical afterglow candidate |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 210506a (aaron tohuvavohu et al. gcn circ. 29947), collecting 4.8 ks of photon counting (pc) mode data between t0+29.0 ks and t0+45.6 ks. three 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): 132.9074 = 08:51:37.78 dec (j2000.0): +4.5999 = +04:35:59.6 error: 6.4 arcsec (radius, 90% conf.) count-rate: (1.46 [+0.89, -0.69])e-3 ct s^-1 distance: 206 arcsec from swift/bat position. source 8: ra (j2000.0): 132.8470 = 08:51:23.29 dec (j2000.0): +4.6632 = +04:39:47.4 error: 7.4 arcsec (radius, 90% conf.) count-rate: (1.72 [+1.01, -0.78])e-3 ct s^-1 distance: 291 arcsec from swift/bat position. flux: (1.05 [+0.62, -0.48])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 9: ra (j2000.0): 132.7917 = 08:51:10.02 dec (j2000.0): +4.6042 = +04:36:15.2 error: 7.9 arcsec (radius, 90% conf.) count-rate: (1.76 [+0.96, -0.76])e-3 ct s^-1 distance: 232 arcsec from swift/bat position. flux: (2.8 [+1.5, -1.2])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) 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/00021430. this circular is an official product of the swift-xrt team. | grb 210506a: swift-xrt observations |
short gamma-ray bursts (sgrbs) are produced on the coalescence of two compact objects such as two neutron stars. these cataclismic events release a large amount of energy in gravitational waves during the coalescence event to a single compact object. we present the results of the study of grb 160410a that, at $z$ = 1.7177, is one of the farthest sgrbs ever detected. the grb afterglow emission was first detected by swift/bat and observed with the x-shooter spectrograph at vlt starting just $\sim$ 8 minutes after the grb. this is one of the best spectra ever obtained on the grb afterglow emission of a sgrb. it allow us to perform for the first time a chemical study of the circumburst medium of a sgrb. the spectrum shows low-ionization features common to long grbs (lgrb), however, high-ionization features are missing. we detect the broad absorption line corresponding to lyman-alpha feature with a measured value for the column density compatible with a damped lyman-alpha absorption (dla) region. we find no evidence for dust depletion. the measured metallicity, [fe/h] = -2.5 $\pm$ 0.2, is low as compared to lgrb-dla systems. late observations with osiris/gtc failed to detect an underlying galaxy at the grb location down to r $>$ 27 mag. the grb ligh-curve is better described by a double-broken power-law and a spectral energy distribution consistent with no extinction. grb 160410a is in contrast with our findings for grb 201221d, a softer sgrb that shows only fe ii and mg ii features at $z$ = 1.045 with line strength consistent with the mean value measured for lgrb environments. the host galaxy is a well detected massive galaxy with low star formation rate. | absorption spectroscopy of grb 160410a: the first complete study of the ism of a short grb |
at 06:53:41 ut, the swift burst alert telescope (bat) triggered and located grb 210419a (trigger=1044032). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 86.862, -65.539 which is ra(j2000) = 05h 47m 27s dec(j2000) = -65d 32' 20" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). as is usual for an image trigger, no obvious variation is visible in the immediately-available lightcurve. the xrt began observing the field at 06:55:49.0 ut, 127.9 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 86.85414, -65.50357 which is equivalent to: ra(j2000) = 05h 47m 24.99s dec(j2000) = -65d 30' 12.9" with an uncertainty of 3.5 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 in excess of the galactic value (7.76 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 5.3 (+3.15/-2.74) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 1.57e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 136 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 0.075. this source lies within the current (sector 37) field-of-view of tess camera 4. 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 210419a: swift detection of a burst |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 210622a (james delaunay et al. gcn circ. 30302), collecting 4.5 ks of photon counting (pc) mode data between t0+171.2 ks and t0+221.6 ks. no x-ray sources have been detected consistent with being within 246 arcsec of the swift/bat-guano position. the 3-sigma upper limit in the field is 0.003 ct s^-1, corresponding to a 0.3-10 kev observed flux of 1.0e-13 erg cm^-2 s^-1 (assuming a typical grb spectrum). an uncatalogued was 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/00021452. this circular is an official product of the swift-xrt team. | grb 210622a: swift-xrt observations |
at 09:43:11 ut, the swift burst alert telescope (bat) triggered and located grb 210712a (trigger=1059881). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 97.337, -35.393 which is ra(j2000) = 06h 29m 21s dec(j2000) = -35d 23' 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 20 sec, followed by lower-level extended emission. the peak count rate was ~2600 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 09:44:32.5 ut, 80.6 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source with an enhanced position: ra, dec 97.3319, -35.3717 which is equivalent to: ra(j2000) = 06h 29m 19.66s dec(j2000) = -35d 22' 18.0" with an uncertainty of 1.9 arcseconds (radius, 90% containment). 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 (8.88 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 6.5 (+5.28/-4.30) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 3.52e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 90 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 0.076. 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 210712a: swift detection of a burst |
after the multi-messenger detection of the binary neutron star merger gw170817, associated with gamma-ray burst (grb) 170817a, one big open question left is the nature of the compact remnant which acts as a central engine for the grb. in the context of cosmological grbs, it has been suggested that x-ray afterglows showing lightcurve plateaus at timescales of order 102 - 104 s since the grb/merger could harbor a long-lived central engine, such as a long-lived highly magnetized ns (magnetar). newly born magnetars have also been proposed as potential gravitational wave (gw) sources. motivated by these considerations, we present first results from a new gw data analysis method (the cross correlation algorithm - cocoa) targeting long-lived gws from magnetars formed in binary ns mergers associated with grbs. we show how our search method improves substantially on previously published results for post-merger gw searches in gw170817, but requires a more restrictive hypothesis on the gw signal properties. we conclude by discussing the prospects for these types of searches in future runs of the ligo detectors. | post-merger gravitational wave searches using the cross-correlation algorithm |
at 20:52:56 ut, the swift burst alert telescope (bat) triggered and located grb 211207a (trigger=1088376). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 149.625, -24.352 which is ra(j2000) = 09h 58m 30s dec(j2000) = -24d 21' 05" 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 4 sec. the peak count rate was ~1500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 20:54:17.2 ut, 80.5 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 149.62449, -24.35970 which is equivalent to: ra(j2000) = 09h 58m 29.88s dec(j2000) = -24d 21' 34.9" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 27 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 (4.94 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.1 (+3.50/-2.89) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 84 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 09:58:29.78 = 149.62408 dec(j2000) = -24:21:31.1 = -24.35863 with a 90%-confidence error radius of about 0.62 arc sec. this position is 3.5 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.45 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.050. burst advocate for this burst is e. ambrosi (elena.ambrosi 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 211207a: swift detection of a burst with an optical counterpart |
at 19:56:44.60 ut, the swift burst alert telescope (bat) triggered and located grb 190829a (trigger=922968). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 44.540, -8.968 which is ra(j2000) = 02h 58m 10s dec(j2000) = -08d 58' 03" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a smaller peak at ~t-50 seconds followed by the main peak around t~0 with a duration of about 15 sec. the peak count rate was ~1500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 19:58:21.9 ut, 97.3 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source with an enhanced position: ra, dec 44.5440, -8.9579 which is equivalent to: ra(j2000) = 02h 58m 10.57s dec(j2000) = -08d 57' 28.6" with an uncertainty of 2.0 arcseconds (radius, 90% containment). this location is 39 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 does not constrain the column density. the initial flux in the 2.5 s image was 7.75e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 106 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. this grb was also reported by the fermi gbm team (gcn #25551), at the time of the first peak. we note the presence of a galaxy sdss j025810.28-085719.2 with z=0.07914 centered at a distance of 10 arcseconds from the xrt location. http://skyserver.sdss.org/dr14/en/tools/explore/summary.aspx?id=1237652899156721762 burst advocate for this burst is s. dichiara (dichiara at umd.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 190829a: swift detection of a burst consistent with a galaxy at z=0.08 |
swift is currently the only mission that can localize a short grb to < 3 arc-minute resolution, or better. in o4 we plan to use swift as a discovery tool for the next ns-ns merger that is detected in gravitational waves by ligo/virgo/kagra in the upcoming o4 run, and rapidly report that location with arc-minute or better localization. although swift's burst alert telescope (bat) may be lucky enough to passively detect a gw related event, given the likely low rate of these events and bat triggering only covering 1/6th of the sky, we need to be proactive to increase the chances of this happening. here we present the news evolutions of the swift telescope that will allow us to deliver this result, using new initiatives. firstly, we talk about the gamma-ray urgent archiver for novel opportunities (guano), a system that proactively dumps otherwise lost bat event data, allowing us to provide a sensitive search for em emission both inside and outside the fov of the bat, with localization capabilities in both cases. we discuss the improvements to swift commanding that allow commands to be sent in real-time, allowing us to not only perform realtime searches for counterparts, but also allows us to realign the spacecraft to more favorably align bat with the location of the merger, based on early warning alerts that are releases by lvk prior to the merger. we also present results from o3 from swift for afterglow searches. | the swift plan for o4: catching ns-ns mergers on the fly |
at 02:25:10 ut, the swift burst alert telescope (bat) triggered and located grb 200410a (trigger=965638). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 299.637, +51.763, which is ra(j2000) = 19h 58m 33s dec(j2000) = +51d 45' 48" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows multiple peaks with a total duration of about 45 sec. the peak count rate was ~1000 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 02:26:51.7 ut, 101.3 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 299.6456, 51.7813 which is equivalent to: ra(j2000) = 19h 58m 34.94s dec(j2000) = +51d 46' 52.5" with an uncertainty of 2.1 arcseconds (radius, 90% containment). this location is 68 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 (2.15 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 2.3 (+2.17/-1.95) 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. there is a possible candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 19:58:35.32 = 299.64717 dec(j2000) = +51:46:53.0 = +51.78138 with a 90%-confidence error radius of about 0.6 arc sec. this position is 3.5 arc sec. from the center of the xrt error circle. the estimated magnitude is 18.71 with a 1-sigma error of about 0.15. no correction has been made for the expected extinction corresponding to e(b-v) of 0.15. burst advocate for this burst is k. k. simpson (kira.simpson1984 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 200410a: swift detection of a burst with a possible optical counterpart |
gamma-ray bursts (grbs) are very energetic cosmological transients. long grbs are usually associated with type ib/c supernovae (sne), and we refer to them as grb-sne. since the associated sn for a given grb is observed only at low redshift, a possible selection effect exists when we consider intrinsically faint sources which cannot be observed at high redshift. thus, it is important to explore the possible relationships between grb and sn parameters after these have been corrected for astrophysical biases due to the instrumental selection effects and redshift evolution of the variables involved. so far, only grb prompt emission properties have been checked against the sne ib/c properties without considering the afterglow (ag). this work investigates the existence of relationships among grb's prompt and ag and associated sn properties. we investigate 91 bidimensional correlations among the sn and grb observables before and after their correction for selection biases and evolutionary effects. as a result of this investigation, we find hints of a new correlation with a pearson correlation coefficient > 0.50 and a probability of being drawn by chance < 0.05. this correlation is between the luminosity at the end of the grb optical plateau emission and the rest-frame peak time of the sn. according to this relation, the brightest optical plateaus are accompanied by the largest peak times. this correlation is corrected for selection biases and redshift evolution and may provide new constraints for the astrophysical models associated with the grb-sne connection. | the quest for new correlations in the realm of the gamma-ray burst-supernova connection |
we have used chandra, hst and the vla to observe a sample of extremely energetic gamma-ray bursts detected by the large area telescope (lat) in a large fraction of cases the burst afterglows show no sign of a jet-break. more to follow. | the nature of the largely unbreakable lat bursts |
"the chandra x-ray observatory observed the position of the short-duration grb 231117a (laha et al., gcn 35071, navaneeth et al., gcn 35072, cattaneo et al., gcn 35075, svinkin et al., gcn 35079, cheung et al., gcn 35081) starting on 2023 november 21 at 06:22:13 ut. we obtained an acis-s observation under proposal 24400307 (pi: fong), with an effective exposure time of ~27 ksec, for a mid-time of 4.3 days post-burst. the x-ray afterglow is clearly detected at high significance. the source is spatially coincident with the optical (e.g., yang et al., gcn 35083, rastinejad et al., gcn 35087, gompertz et al., gcn 35088) and radio (rhodes et al., gcn 35097, schroeder et al., gcn 35114) afterglows at the position: ra (j2000) = 22:09:33.37 dec (j2000) = 13:31:20.0 we note that, similar to the reported optical positions, the chandra source is just outside the 90% confidence region of the latest xrt position. we measure a 0.3-10 kev flux for the chandra afterglow of fx ~ 2e-13 erg/s/cm^2. we find that the xrt light curve beyond ~300 seconds post-burst can be modeled with a single power-law with fx ~ t^-0.6, and that the chandra observation is fully consistent with this power law. we thank the chandra staff for rapid approval and planning of these observations." | grb 231117a: chandra afterglow detection |
at 01:29:08 ut, the swift burst alert telescope (bat) triggered and located grb 231230a (trigger=1205319). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 245.197, +58.120 which is ra(j2000) = 16h 20m 47s dec(j2000) = +58d 07' 11" 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 30 sec. the peak count rate was ~1500 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 01:32:45.0 ut, 216.3 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 245.21706, 58.12324 which is equivalent to: ra(j2000) = 16h 20m 52.09s dec(j2000) = +58d 07' 23.7" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 39 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 (1.31 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 4.3 (+4.82/-3.83) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 145 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 0.015. 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 231230a: swift detection of a burst |
at 19:16:13 ut, the swift burst alert telescope (bat) triggered and located grb 180614a (trigger=841548). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 3.157, +46.943, which is ra(j2000) = 00h 12m 38s dec(j2000) = +46d 56' 34" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows a couple peaks with a duration of about 25 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 19:17:19.1 ut, 65.6 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 3.07620, 46.95342 which is equivalent to: ra(j2000) = 00h 12m 18.29s dec(j2000) = +46d 57' 12.3" with an uncertainty of 4.0 arcseconds (radius, 90% containment). this location is 202 arcseconds from the bat onboard position. 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. this position is more than 2-sigma away from the bat position, and so possibly unrelated to the trigger. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.14 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 68 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' image covers none of the xrt error circle. data from the list of sources generated on-board are not available at this time. 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/too.html.) | grb 180614a: swift detection of a burst |
the distribution of jet angles for short gamma-ray bursts (sgrbs) is critical to constrain as it directly affects the true energy scale and event rate, which is of particular interest in the midst of the new lvk run for next year. our current knowledge of the jet angle distribution comes almost exclusively from x-ray observations at >1 day after the burst. here, we propose for a chandra ddt observation to continue to monitor the afterglow of sgrb 211106a and constrain its late-time collimation up to ~60 days post-trigger, either from the detection of the x-ray afterglow, which places a lower limit on the opening angle at >15 deg, or a non-detection of the afterglow, indicating a jet break has occurred and constraining the jet break to 20-25 deg. we have broad-band afterglow observations, which will be leveraged to provide the tightest constraints on the jet angle. | tracking the x-ray emission of the remarkable sgrb 211106a |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 200623a (james delaunay et al. gcn circ. 28013), collecting 5.0 ks of photon counting (pc) mode data between t0+37.8 ks and t0+50.1 ks. 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): 242.2874 = 16:09:8.97 dec (j2000.0): +53.5321 = +53:31:55.6 error: 4.4 arcsec (radius, 90% conf. [enhanced position]) count-rate: (3.5 [+1.2, -1.0])e-3 ct s^-1 distance: 406 arcsec from swift/bat position. flux: (1.09 [+0.39, -0.32])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 242.1106 = 16:08:26.55 dec (j2000.0): +53.3466 = +53:20:47.9 error: 5.1 arcsec (radius, 90% conf.) count-rate: (1.19 [+0.79, -0.56])e-3 ct s^-1 distance: 462 arcsec from swift/bat position. source 3: ra (j2000.0): 241.9966 = 16:07:59.18 dec (j2000.0): +53.4786 = +53:28:42.8 error: 5.0 arcsec (radius, 90% conf.) count-rate: (3.10 [+1.11, -0.91])e-3 ct s^-1 distance: 272 arcsec from swift/bat position. flux: (1.96 [+0.70, -0.58])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 1 is consistent with a known quasar, [vv2006] j160908.9+533153. source 2 is poorly detected and is likely to be a background fluctuation. source 3 is not a known x-ray source, its position is consistent with a background galaxy, sdss j160758.62+532842.2 (d'avanzo et al., gcn #28021). follow up observation of source 3 are planned to be carried out at the end of this week. 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/00021005. this circular is an official product of the swift-xrt team. | grb 200623a: swift-xrt observations |
at 08:21:16 ut, the swift burst alert telescope (bat) triggered and located grb 180626a (trigger=844615). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 243.567, +14.764 which is ra(j2000) = 16h 14m 16s dec(j2000) = +14d 45' 52" 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 ~3400 counts/sec (15-350 kev), at ~-2 sec after the trigger. the xrt began observing the field at 08:23:16.9 ut, 120.0 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 243.57544, 14.75598 which is equivalent to: ra(j2000) = 16h 14m 18.11s dec(j2000) = +14d 45' 21.5" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 41 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 in excess of the galactic value (3.47 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.2 (+2.28/-2.05) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 123 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 16:14:18.12 = 243.57551 dec(j2000) = +14:45:25.5 = 14.75707 with a 90%-confidence error radius of about 0.81 arc sec. this position is 5.1 arc sec. from the center of the xrt error circle. the estimated magnitude is 20.71 with a 1-sigma error of about 0.23. no correction has been made for the expected extinction corresponding to e(b-v) of 0.04. 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 180626a: swift detection of a burst with an optical counterpart |
certain features of gamma-ray bursts (grbs) are hard to explain in thecontext of the standard forward shock (fs) model. specifically, the x-raylight curves of a few grb afterglows show a steep drop that is not seenin the optical. a solution is that the early x-ray emission is poweredby the spin-down of a newly born magnetar. when this ceases, the x-rayemission drops. in contrast, the optical is entirely fs emission. ifthis model holds true, the late x-ray flux should decay similarly tothe optical. we propose to test this scenario with late observations of2 swift grbs. by measuring the late x-ray flux, we can infer the ejectaenergy and how the magnetar central engine distributes the energy of theevent into different channels. the predicted flux, too faint for swift,requires xmm-newton observations. | late x-ray observations to unveil non-forward shock components in grb afterglows |
torsional oscillations excited in the neutron star crust strongly depend on the crust elasticity. once one would identify the observed frequencies of a neutron star with crustal torsional oscillations, one might extract the crust or neutron star properties. in practice, it has been suggested that the crust equation of state (or nuclear saturation parameters) could be constrained by identifying the quasi-periodic oscillations (qpos) observed in the afterglow of the magnetar giant flares with crustal torsional oscillations. on the other hand, recently high-frequency qpos are discovered in the gamma-ray burst, grb 200415a. unlike the previous magnetar qpos, only high-frequency qpos could be observed in grb 200415a because of the short duration of observation. nevertheless, we can identify this observation in the same framework as in the previous magnetar qpos by systematically examining the crustal torsional oscillations, through which we can constrain the nuclear saturation parameters. furthermore, by consistently considering the neutron star mass and radius expected from the resultant nuclear saturation parameters, we can also constrain the neutron star mass and radius, which are more or less consistent with the other constraints from the astronomical observations. japan society for the promotion of science (jsps) kakenhi grant numbers jp19kk0354 and jp21h0108. | constraint on the mass and radius of grb 200415a using the high-frequency qpos |
since their discovery in the late 1960s gamma-ray burst (grb) emission has been deeply investigated with the help of the huge amount of data collected covering the entire electromagnetic spectrum. this large and broadband dataset was essential to constitute a general picture describing the grb physics, revealing the most credible underlying physical processes and environmental conditions ongoing at the grb site. a key leap in the comprehension of the grb physics have been achieved recently, thanks to the detection of the newly energetic component in the very high energy (vhe, e > 100 gev) domain. the possible presence of a tev spectral window in grbs was predicted and theorized for several decades, but the first observational proofs of its existence were reached only in 2019 thanks to the discoveries claimed by the magic and h.e.s.s. telescopes. grb190114c was successfully detected in the tev band by the magic telescopes starting from around one minute after its trigger time and lasting for nearly 40 minutes. a successful follow-up campaign was performed and the multi-wavelength afterglow emission of the event was collected from 1 to about 2 × 1017 ghz. such very broad dataset allows to perform unique studies on the radiation mechanisms and on the physical properties of such event. in this contribution i will describe the main results and the theoretical interpretations that have been derived from the multi-wavelength dataset of grb190114c. in particular, the description of the tev component detected by the magic telescopes as produced via the synchrotron self-compton (ssc) mechanism and its connection with the emission at lower energy bands will be presented. such studies are a fundamental starting point for the interpretation of the current and upcoming events that will be observed in the vhe domain. | theoretical implications on the very high energy emission from grb 190114c |
grb 221009a was the brightest gamma-ray burst (grb) detected since the start of grb observations. even though it saturated fermi-gbm, it presents a rich and unique data set to test theoretical models of gamma-ray production. we present spectral analysis of the pulses not affected by instrumental saturation and confront the synchrotron emission model with the observations. interestingly, the afterglow is also detected by gbm. we determine the transition from prompt emission to afterglow, and derive the lorentz factor of the outflow using multiple methods. | physical properties of the brightest gamma-ray burst based on observations by the fermi gamma-ray burst monitor |
at 22:29:51 ut, the swift burst alert telescope (bat) triggered and located grb 170330a (trigger=744773). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 283.326, -13.437, which is ra(j2000) = 18h 53m 18s dec(j2000) = -13d 26' 12" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows a single peak with a duration of about 10 sec. the peak count rate was ~1000 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 22:31:29.6 ut, 98.4 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 283.3323, -13.4301 which is equivalent to: ra(j2000) = +18h 53m 19.75s dec(j2000) = -13d 25' 48.4" with an uncertainty of 5.9 arcseconds (radius, 90% containment). this location is 33 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 150 seconds with the white filter starting 108 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 0.45. burst advocate for this burst is p. d'avanzo (paolo.davanzo 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/too.html.) | grb 170330a: swift detection of a burst |
the distribution of jet angles for short gamma-ray bursts (sgrbs) is critical to constrain because it directly affects the true energy scale and event rate. the event rate is of particular interest in the gravitational wave era. our current knowledge of the jet angle distribution comes almost exclusively from x-ray observations at >1 day after the burst. here, we propose for chandra too observations to monitor a sgrb afterglow and constrain its collimation, either from the detection of a jet break, or the non-detection of a break to place a lower limit of >5-20 deg. a precise calculation of the jet angle also requires broad-band afterglow observations. with our ongoing radio and optical too programs, our group is uniquely poised to provide the tightest constraints on the jet angle. | the late-time x-ray behavior of short gamma-ray bursts: implications for energetics and rates |
long gamma-ray bursts (grbs) with a plateau phase in their x-ray afterglows obeys a three-dimensional (3d) relation (dainotti et al. 2016), between the rest-frame time at the end of the plateau, ta, its corresponding x-ray luminosity, la, and the peak luminosity in the prompt emission, lpeak, an extension of the two-dimensional dainotti relation. this 3d relation identifies a grb fundamental plane whose existence we here confirm. we extend the original analysis with x-ray data untill july 2016 gathering 183 swift grbs with afterglow plateaus and known redshifts. we compare several grb categories, such as shorts with extended emission, see, x-ray flashes, grbs associated with sne, a sample of only long-duration grbs (132), selected from the total sample by excluding grbs of the previous categories, and the gold sample, composed by grbs with light curves with good data coverage and relatively flat plateaus. the relation planes for each of these categories are not statistically different from the gold fundamental plane, with the exception of the see, which are hence identified as a physically distinct class of objects. the gold fundamental plane has an intrinsic scatter smaller than any plane derived from the other sample categories. thus, the distance of any particular grb category from this plane becomes a key parameter. additionally, we tested this 3d relations by using grbs observed at high energy, namely the peak luminosity values derived by the fermi-gamma ray burst monitor (gbm). the 3d relation is also confirmed for grbs observed by the gbm, thus showing its independence from the energy range. furthermore, we computed the several category planes with t*a as a dependent parameter obtaining for each category smaller intrinsic scatters (reaching a reduction of $24\%$ for the long grbs). the fundamental plane is independent from several prompt and afterglow parameters. | a study of the gamma-ray burst fundamental plane |
at 21:05:52 ut, the swift burst alert telescope (bat) triggered and located grb 211023b (trigger=1080859). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 170.302, +39.137 which is ra(j2000) = 11h 21m 12s dec(j2000) = +39d 08' 14" 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 2 sec. the peak count rate was ~1500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 21:07:27.3 ut, 95.3 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 170.31048, 39.13595 which is equivalent to: ra(j2000) = 11h 21m 14.52s dec(j2000) = +39d 08' 09.4" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 23 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 (2.30 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.5 (+2.51/-2.21) 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. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 11:21:14.31 = 170.30963 dec(j2000) = +39:08:08.8 = 39.13578 with a 90%-confidence error radius of about 0.79 arc sec. this position is 3.2 arc sec. from the center of the xrt error circle. the estimated magnitude is 19.32 with a 1-sigma error of about 0.16. no correction has been made for the expected extinction corresponding to e(b-v) of 0.024. we note that this is swift's 1500th grb. burst advocate for this burst is s. dichiara (dichiara at umd.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 211023b: swift detection of a possibly short burst with an optical counterpart |
at 22:02:18 ut, the swift burst alert telescope (bat) triggered and located grb 210323a (trigger=1038247). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 317.952, +25.378 which is ra(j2000) = 21h 11m 49s dec(j2000) = +25d 22' 40" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single spike structure with a duration of about 1 sec. the peak count rate was ~10,000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 22:03:43.6 ut, 85.2 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 317.94609, 25.36990 which is equivalent to: ra(j2000) = 21h 11m 47.06s dec(j2000) = +25d 22' 11.6" with an uncertainty of 3.5 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. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.17 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 5.9 (+3.84/-3.14) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 88 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 0.132. 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 210323a: swift detection of a short burst |
the optical afterglow of the recently discovered bright gamma-ray burst grb180914b (gcn 23226, 23231, 23232, 23234) was detected on stacked 3 x 300 sec ccd frames taken with the 0.6/0.9m schmidt telescope through bvri filters on 2018-09-18.94 ut (4.18 days after the initial burst in the observer frame). | detection and photometry of the optical afterglow of the gamma-ray burst grb180914b |
at 04:41:15 ut, the swift burst alert telescope (bat) triggered and located grb 190718a (trigger=915091). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 336.531, -41.221 which is ra(j2000) = 22h 26m 07s dec(j2000) = -41d 13' 13" 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 ~1700 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 04:42:21.5 ut, 66.4 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 336.57614, -41.20264 which is equivalent to: ra(j2000) = 22h 26m 18.27s dec(j2000) = -41d 12' 09.5" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 138 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 in excess of the galactic value (1.24 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 4.3 (+2.81/-2.43) 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 0.01. burst advocate for this burst is v. d'elia (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 190718a: swift detection of a burst |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 170510a (bissaldi et al. gcn circ. 21080) in a series of observations tiled on the sky. the total exposure time is 4.7 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 1.4 ks. the data were collected between t0+24.3 ks and t0+36.2 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): 160.15394 = 10:40:36.95 dec (j2000.0): -39.21244 = -39:12:44.8 error: 2.3 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0630 [+0.0091, -0.0090] ct s^-1 distance: 794 arcsec from fermi/lat position. flux: (1.76 [+0.26, -0.25])e-12 erg cm^-2 s^-1 (observed, 0.3-10 kev) two catalogued sources were 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 http://www.swift.ac.uk/xrt_products/tiled_grb00067. this circular is an official product of the swift-xrt team. | grb 170510a: swift-xrt observations |
at 07:09:01 ut, the swift burst alert telescope (bat) triggered and located grb 201221a (trigger=1013852). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 214.477, -45.411 which is ra(j2000) = 14h 17m 55s dec(j2000) = -45d 24' 38" 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 ~800 counts/sec (15-350 kev), at ~10 sec after the trigger. the xrt began observing the field at 07:11:17.8 ut, 136.5 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 214.47885, -45.41606 which is equivalent to: ra(j2000) = 14h 17m 54.92s dec(j2000) = -45d 24' 57.8" with an uncertainty of 3.8 arcseconds (radius, 90% containment). this location is 18 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 (9.32 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 5.3 (+4.59/-3.72) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 141 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 0.11. 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 201221a: swift detection of a burst |
we propose to design, build, and fly burstcube: a 6u cubesat with four csi detectors sensitive to gamma-rays from 10 kev to 1 mev. burstcube autonomously detects gamma-ray bursts (grbs) onboard, rapidly downlinking data for timing and localizations that are disseminated to ground-based observers to maximize the chances of detecting fading broadband afterglows. the burstcube mission has three objectives: provide astrophysical context and rapid localizations for high-significance ligo/virgo detections coincident with short grbs; correlate short grbs with ligo/virgo sub-threshold signals, effectively increasing the gravitational wave detection volume; monitor the gamma-ray sky in search of transient and variable sources including solar flares, flaring galactic binaries magnetar outbursts, and flaring active galaxies. the discovery of gws and their astrophysical counterparts is one of the most important scientific topics of this decade (astro2010 decadal survey). | burstcube |
the distribution of jet angles for short gamma-ray bursts (sgrbs) is critical to constrain as it directly affects the true energy scale and event rate. the event rate is of particular interest in the gravitational wave era. our current knowledge of the jet angle distribution comes almost exclusively from x-ray observations at >1 day after the burst. here, we propose for a chandra too observation to continue to monitor the afterglow of sgrb 210726a and constrain its collimation, either from the detection of the x-ray afterglow, which places a lower limit on the opening angle at >35 deg, or a non-detection of the afterglow, indicating a jet break has occurred and constraining the jet break to 13-35 deg. we have broad-band afterglow observations, which will be leveraged to provide the tightest constraints on the jet angle. this would be the first detection of a cosmological sgrb afterglow at >50 days, complementing the longest lasting detections of an sgrb radio afterglow. | the wide angle outflow of sgrb 210726a |
swift burst alert telescope (bat) triggered and located grb 210504a (trigger=1046782), with the trigger time most likely between 13:40 and 13:58 ut. no bat information is available at this moment. xrt began observing the field of the new trigger at 13:58:28 ut. in a promptly-downlinked image we find an x-ray source at ra,dec = 222.3933, -30.5322 which is equivalent to ra (j2000) = 14:49:34.4 dec (j2000) = -30:31:56 with an estimated uncertainty of about 10". we currently have very limited data products and are awaiting the full data after a ground station pass to further characterise this object. uvot took a finding chart exposure of 150 seconds with the white filter. 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 extinction in the milky way. 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 210504a: swift detection of a burst |
at 21:10:37 ut, the swift burst alert telescope (bat) triggered and located grb 230322b (trigger=1161127). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 16.565, -47.729 which is ra(j2000) = 01h 06m 16s dec(j2000) = -47d 43' 42" 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 ~900 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 21:12:31.7 ut, 113.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 16.55359, -47.70106 which is equivalent to: ra(j2000) = 01h 06m 12.86s dec(j2000) = -47d 42' 03.8" with an uncertainty of 1.9 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. 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 (2.48 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.5 (+2.99/-2.59) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 118 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 01:06:12.85 = 16.55353 dec(j2000) = -47:42:02.8 = -47.70079 with a 90%-confidence error radius of about 0.62 arc sec. this position is 0.7 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.60 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.017. 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 230322b: swift detection of a burst with optical counterpart |
at 18:20:38 ut, the swift burst alert telescope (bat) triggered and located grb 220118a (trigger=1093742). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 192.274, +22.909 which is ra(j2000) = 12h 49m 06s dec(j2000) = +22d 54' 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 20 sec. the peak count rate was ~1400 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 18:22:08.3 ut, 90.3 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 192.26936, 22.91600 which is equivalent to: ra(j2000) = 12h 49m 04.65s dec(j2000) = +22d 54' 57.6" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 29 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 (2.25 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.4 (+2.60/-2.24) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 4.57e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 99 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 12:49:04.53 = 192.26888 dec(j2000) = +22:54:56.2 = 22.91562 with a 90%-confidence error radius of about 0.75 arc sec. this position is 1.8 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.83 with a 1-sigma error of about 0.15. no correction has been made for the expected extinction corresponding to e(b-v) of 0.025. 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 220118a: swift detection of a burst with an optical counterpart |
the main aim of this thesis is to study the afterglow phase in the gamma-ray burst (grb) light curves to better understand the physics and the radiation processes driving these phenomena, and to eventually use this knowledge in search for a method to turn grbs into cosmological standard candles. in the proceedings a sample of 176 grb light curves in the x-ray energy band, taken from the swift catalogue, is analysed. the grb physical parameters, like emitted energy, luminosity, temporal decay index, spectral index, and so forth, of the afterglow phase were investigated. in particular, the correlations among these parameters were studied, as the well known correlation between the luminosity at the end of the plateau phase, lx,a, and the end time of the plateau phase itself, t ∗x,a (dainotti et al. 2008, hereafter lt correlation). in the investigation of these correlations the selection effects influencing the measurements were studied and published in the paper dainotti, del vecchio, nagataki, and capozziello (2015b). as a result of further analysis, a correlation between the temporal decay index, αx,a, and the relative luminosity, log (lx,a/llt) (the ratio of lx,a to the value of the luminosity of the lt correlation best fit line at the same time), is discovered and a systematic effect on the lt correlation depending on αx,a is revealed. a novelty of the presented analysis comes from the performed systematic study – using a large data sample – of the x-ray afterglow light curve decaying phase and the discovery of a new correlation between the light curve decay speed and the characteristic afterglow luminosity (del vecchio, dainotti & ostrowski, apj, 828, 36 (2016)). the study of this correlation is useful in investigation of the nature and the properties of the grb surrounding medium, which on the other hand can play an important role in shaping the grb emission. also, a method for correcting the afterglow luminosity applying measurements of the afterglow power-law decay index was developed and tested within an assumed simple model. unfortunately, the method resembling the one by phillips (1993) for supernovae (sne) ia, has a limited effect in grb standardization attempt due to largely scattered data. | new study of afterglow light curves in gamma ray bursts |
at 20:14:09 ut, the swift burst alert telescope (bat) triggered and located grb 210724a (trigger=1061482). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 227.407d, -6.274d which is ra(j2000) = 15h 09m 38s dec(j2000) = -06d 16' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). due to a telemetry outage the bat lightcurve is not immediately available. however, the trigger information indicates a duration of at least 4 seconds. the xrt began observing the field at 20:17:09.0 ut, 179.8 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 227.4118, -6.2911 which is equivalent to: ra(j2000) = 15h 09m 38.83s dec(j2000) = -06d 17' 27.8" with an uncertainty of 1.9 arcseconds (radius, 90% containment). 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 8.23 x 10^20 cm^-2 (willingale et al. 2013). 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 0.097. 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 210724a: swift detection of a burst |
we have analysed 2.7 ks of photon counting (pc) mode xrt data for the swift-bat-detected burst grb 210218a (stamatikos et al. gcn circ. 29537), collected between t0+170 ks and t0+210 ks s. one uncatalogued x-ray source has been detected consistent with being within 296 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 3: ra (j2000.0): 47.3236 = 03:09:17.67 dec (j2000.0): +35.3240 = +35:19:26.5 error: 4.8 arcsec (radius, 90% conf.) count-rate: (5.6 [+2.0, -1.6])e-3 ct s^-1 distance: 164 arcsec from swift-bat position. flux: (1.03 [+0.36, -0.29])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) two 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/01033328. this circular is an official product of the swift-xrt team. | grb 210218a: swift-xrt observations |
several gamma-ray burst (grb) afterglow light curves show a so-called "plateau" phase in the x-rays. theoretical models predict that a long-lived central engine, such as a highly magnetized neutron star (magnetar), could power this plateau phase by injecting energy into the afterglow shock. under the hypothesis that the newly-born magnetar is secularly unstable, its presence could be probed directly by searching for long-lived gravitational waves (gws) during the plateau. in this work, we estimate the number of grbs that could be potential targets for further long-duration gw signal searches. we considered all grbs detected by the swift burst alert telescope (bat) from april 2019 to october 1st, corresponding to advanced ligo third observing run (o3). for completeness, we also extended our analysis to the past runs, advanced ligo first and second observing runs (o1, o2) and initial ligo 6th science run (s6). overall, we estimate that in o2, o1 and s6 each, ≈ 10% of swift-triggered grbs show an x-ray plateau with at least 1000 s of double coincidence time from the ligo detectors. our initial analysis for o3 is compatible with our results from the past runs. | grbs with afterglow plateaus during ligo s6/o1/o2/o3 runs |
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