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following the discovery of the remarkable binary neutron star merger gw170817 by the ligo and virgo collaborations, much research has been conducted to uncover the nature of its post-merger remnant. gw170817 was accompanied by a gamma-ray burst (grb), an optical kilonova, and a radio-to-x-ray-emitting structured jet. several theoretical scenarios predict that, once the jet emission fades sufficiently, the kilonova ejecta itself may power a late-time radio flare associated with the fastest ejecta tail. this late-time radio emission can reveal important information on the nature of the post-merger remnant (neutron star versus black hole) and can be used as a tool to find nearby, gw170817-like neutron star mergers years after they have occurred. in this context, i will present the results, now published in apj, of an observing campaign carried out with the jansky vla aimed at determining whether short grbs in the swift/bat sample lacking accurate localization, ones with no detected afterglow, could have originated from events like gw170817. | a search for kilonova radio flares in a sample of swift/bat short grbs |
at 00:12:41 ut, the swift burst alert telescope (bat) triggered and located grb 210905a (trigger=1071993). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 309.062, -44.431 which is ra(j2000) = 20h 36m 15s dec(j2000) = -44d 25' 50" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of at least 30 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 00:14:13.0 ut, 91.7 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 309.04815, -44.43959 which is equivalent to: ra(j2000) = 20h 36m 11.56s dec(j2000) = -44d 26' 22.5" with an uncertainty of 7.0 arcseconds (radius, 90% containment). this location is 47 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 1.23e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 250 seconds with the u 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 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 0.034. burst advocate for this burst is e. sonbas (edasonbas at yahoo.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 210905a: swift detection of a burst |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 231017a (gcn circ. 34824, delaunay et al.), collecting 4.2 ks of photon counting (pc) mode data between t0+32.7 ks and t0+101.7 ks. one uncatalogued x-ray source has been detected consistent with being within 493 arcsec of the swift/bat-guano 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 2: ra (j2000.0): 86.1666 = 05:44:39.99 dec (j2000.0): +56.7487 = +56:44:55.3 error: 8.4 arcsec (radius, 90% conf.) count-rate: (2.09 [+1.11, -0.84])e-3 ct s^-1 distance: 301 arcsec from swift/bat-guano position. flux: (3.3 [+1.8, -1.3])e-14 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/00021623. this circular is an official product of the swift-xrt team. | grb 231017a: swift-xrt observations |
it is widely known that the x-ray afterglows from long-duration gamma ray bursts (grbs) are often associated with energetic type ic supernovae and that they approximately obey a universal scaling law. here, we discuss a model for x-ray emission from accelerated relativistic electrons within an outgoing relativistic shock. we show that such a universal scaling imposes three constraints: 1) the shock energy is nearly the same for all bursts independently of when the shock arrives at the power-law regime, i.e. the energy in the outgoing shock (∼ 1051 ergs) is independent of the observed grb luminosity; 2) in the power-law epoch, the shock propagates through an optically thin low-density (∼ 1 cm-3) medium; 3) the shock radiates adiabatically. these facts suggest that the late-time power-law afterglow emission derives from material in the associated supernova that is shocked by the grb. we argue that the correlation of the observed grb energy with the luminosity and duration of the plateau suggests that: 1) dimmer grbs correspond to the transport of the grb shock through more material during breakout; and 2) nevertheless, all grbs energize the outgoing shock to the same energy. we suggest that these points are most consistent with the initial grb engine occurring at different radii within the expanding sn shell as in the induced gravitational collapse paradigm. | constraints on the source for gamma-ray bursts from observed x-ray afterglows |
gamma-ray bursts (grbs) are the most energetic electromagnetic transients in universe, spewing out intense bursts of photons from kev to tev energies with a duration of a few milliseconds up to days. depending on the duration, grbs are classified into two types: short grbs (sgrbs) and long grbs (lgrbs) with a duration of less than 2s and more than, respectively. in the case of lgrbs, the collapse of a massive star produces an ultra-relativistic jet which gives rise to a highly variable and luminous gamma-ray emission. this prompt emission is then followed by multiwavelength afterglow emission due to the external dissipation of the jet in the circumburst medium. in most cases, the fermi/lat grbs emission follows a regular decay pattern as expected from the standard afterglow model. however, some of the lat-grbs show slower decay. in this work, we select such grbs from the latest fermi/lat catalog and quantify the disagreement between the observed emission and the prediction of the afterglow emission. in addition to that, we also studied the x-ray light curves in order to evaluate these cases in multi-wavelength scenarios. | joint study of fermi/lat and swift/xrt detected gamma-ray bursts with extended afterglow emission |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 170524b (barthelmy et al. gcn circ. 21142), collecting 2.1 ks of photon counting (pc) mode data between t0+119.5 ks and t0+126.8 ks. 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 1: ra (j2000.0): 90.86806 = 06:03:28.33 dec (j2000.0): -17.08282 = -17:04:58.2 error: 2.3 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0240 +/- 0.0038 ct s^-1 distance: 18 arcsec from swift/bat position. flux: (7.1 +/- 1.1)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 http://www.swift.ac.uk/too_grbs/00020775. this circular is an official product of the swift-xrt team. | grb 170524b: swift-xrt observations |
recent space- and ground-based studies of the circumgalactic medium around galaxies have revealed the dynamic interplay between the galaxy ecosystem and surrounding cgm using bright background quasars. here, we extend this investigation of the cgm to higher redshifts by using the bright afterglows of gamma-ray bursts as background sources. this provides a unique opportunity to probe the host galaxy ism and its surrounding cgm together. we compiled a sample of 25 high-resolution (r > 8000) and high-quality (typical s/n ~ 20) rest-frame uv spectra of grb afterglows with a redshift range (1.5 < z < 5.9) obtained using keck-hires, vlt-uves, and vlt-x-shooter spectrographs. we fit multi-component voigt profiles to several absorption lines of both high-ionization (o vi, c iv, si iv, etc) and low-ionization species (si ii, c ii, fe ii, etc) to extract the column densities (n), doppler parameters (b) and line-centroids. the preliminary results of our analysis on the kinematics and physical properties of the ism and cgm of these grb hosts are presented here. | cgm-grb: a survey of the circumgalactic medium around grb hosts |
fast radio bursts (frbs) are brief radio transients originating from ~gpcdistances. most models for frbs, including the leading magnetar modelsexpect high-energy (0.1-100 kev) counterparts and afterglows to frbs. therecent detection of a galactic frb with a hard x-ray burst from magnetarsgr 1935+2154 lends support to this picture. however, most frbs are toofar for current x-ray telescopes to detect afterglow emission. we proposeto leverage the high frb detection rate of the chime/frb system and alow-latency localization pipeline to trigger xmm-newton observations offrbs at distances nearer than 50 mpc to observe within 12 hrs of the frbdetection. the sensitivity of xmm-newton and the proximity will allowus to detect afterglows 1000x fainter than previous observations. | search for the x-ray afterglows from the nearest fast radio bursts |
gamma-ray bursts (grbs) are energetic transients originating in a violent explosion of a massive star or merger of two compact objects in a binary system. these explosions create a relativistic blastwave which inevitably collides with the circumburst medium and results in external shocks. the emission produced thereby is the afterglow observed in grbs after the initial prompt phase. the properties of the emitting region, i.e., non-thermal particle spectrum, magnetic amplification, and micro-physical parameters, etc., can be probed by monitoring and modelling the afterglow radiation. the recent detection of very high energy (vhe, > 100 gev) gamma rays from grbs has opened a possibility to test theoretical models such as the synchrotron self-compton (ssc) in grbs till late times in the afterglow phase. we find that the ssc model explains the afterglow observations of magic-detected grb 190114c and h.e.s.s.-detected grb 180720b. | synchrotron and synchrotron self-compton emission components in grbs detected at very high energies |
in this study, we will introduce some special events, such as grbs 081029, 100814a and 111209a. unexpected features, such as multiple x-ray flares and significant optical rebrightenings, are observed in their afterglow light curves, unveiling the late-time activities of the central engines. here, we will summarize our previous numerical results of these three bursts by using the energy injection model. especially, we will focus on grb 100814a, with an early-time shallow decay phase and a late-time significant rebrightening in its optical afterglow light curve. to explain the complex multi-band afterglow emission of grb 100814a, we invoke a magnetar with spin evolution as its central engine. we argue that the optical shallow decay phase and the x-ray plateau are due to energy injection from t he magnetar in its early spin-down stage, while the significant optical rebrightening observed at late time naturally comes from the spin-up process of the magnetar, which is caused by subsequent fall back accretion. | energy injections in gamma ray bursts |
gamma-ray bursts (grbs) are promising tools to probe the universe. especially, we can get constraints on cosmological parameters with the help of grb luminosity relations. recently, a tight l-t-e relation has been found. this relation involves a special subclass of grbs, i.e., grbs have x-ray plateaus in their x-ray afterglows. the isotropic γ-ray energy of the prompt grb (eγ,iso) are linked with the duration of the plateau phase (ta) and the x-ray luminosity at the end of the plateau phase (lx ) through this relation. beside this relation, we find that lx and ta also relate to the spectral peak energy (ep) and we call this relation the l-t-ep relation. when using these relations to constrain the cosmological parameters, we find the l-t-e relation is insensitive to the cosmological parameters and both of these relations suffer from redshift evolution. we manage to correct the redshift evolution and use the de-evolved l-t-ep relation to constrain the cosmological parameters. we get the best-fit result as ω = 0.389-0.141+0.202 (1σ) for the flat λcdm model. our result is consistent with that from other probes within 1σ confidence level. joint constraint on cosmological parameters is presented. | probe the universe by using gamma-ray bursts with x-ray plateaus |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 221206b, collecting 4.8 ks of photon counting (pc) mode data between t0+28.7 ks and t0+45.0 ks. no x-ray sources have been detected within the swift/bat-guano error circle. the 3-sigma upper limit in the field ranges from ~0.002 to ~0.003 ct s^-1, corresponding to a 0.3-10 kev observed flux of 7.7e-14 to 1.0e-13 erg cm^-2 s^-1 (assuming a typical grb spectrum). five 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/00021532. this circular is an official product of the swift-xrt team. | grb 221206b: swift-xrt observations |
gamma-ray bursts (grbs) are the most luminous objects known: they outshine their host galaxies making them ideal candidates for probing large-scale structure. earlier, the angular distribution of different grbs (long, intermediate and short) has been studied in detail with different methods and it has been found that the short and intermediate groups showed deviation from the full randomness at different levels (e.g. vavrek, r., et al. 2008). however these result based only angular measurements of the batse experiment, without any spatial distance indicator involved.currently we have more than 361 grbs with measured precise position, optical afterglow and redshift, mainly due to the observations of the swift mission. this sample is getting large enough that it its homogeneous and isotropic distribution a large scale can be checked. we have recently (horvath, i. et al., 2014) identified a large clustering of gamma-ray bursts at redshift z ~ 2 in the general direction of the constellations of hercules and corona borealis. this angular excess cannot be entirely attributed to known selection biases, making its existence due to chance unlikely. the scale on which the clustering occurs is disturbingly large, about 2-3 gpc: the underlying distribution of matter suggested by this cluster is big enough to question standard assumptions about universal homogeneity and isotropy. | anomalies in the grbs' distribution |
at 12:40:50 ut, the swift burst alert telescope (bat) triggered and located grb 190706b (trigger=913302). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 107.449, -29.584, which is ra(j2000) = 07h 09m 48s dec(j2000) = -29d 35' 02" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows a few peaks with a total duration of about 25 sec. the peak count rate was ~1100 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 12:42:24.4 ut, 94.4 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 107.46161, -29.55341 which is equivalent to: ra(j2000) = 07h 09m 50.79s dec(j2000) = -29d 33' 12.3" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 116 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 2.40 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 100 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 a. tohuvavohu (aaronb at swift.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 190706b: swift detection of a burst |
at 16:08:48 ut, the swift burst alert telescope (bat) triggered and located grb 230816a (trigger=1185673). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 328.375, +37.828 which is ra(j2000) = 21h 53m 30s dec(j2000) = +37d 49' 43" 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 25 sec. the peak count rate was ~1900 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 16:10:18.4 ut, 90.2 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 328.44552, 37.85549 which is equivalent to: ra(j2000) = 21h 53m 46.92s dec(j2000) = +37d 51' 19.8" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 223 arcseconds from the bat onboard position. 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 (2.90 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 3.7 (+3.48/-2.91) x 10^21 cm^-2 (90% confidence). 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 0.311. burst advocate for this burst is m. h. siegel (siegel at swift.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 230816a: swift detection of a burst |
gamma-ray bursts (grbs) are believed collimated, we using a large optical afterglow sample f to investigate the jet break phenomenons in grbs. we also use the jet break candidates to test the typical experimental luminosity correlations. | gamma-ray burst jets revisited |
swift has performed follow-up observations of the fermi/gbm-detected burst grb 220426a (gcn circ. 31950, 31955), which was also detected by swift/bat-guano (gcn circ. 31954), konus-wind (gcn circ. 31959), integral/spi-acs, and hend/mars-odyssey (gcn circ. 31958). the xrt observations consist of three tiles of 1 ks each, to cover the grb error region. the data were acquired between 45 and 47 hours after the burst and are entirely in pc mode. one bright, uncatalogued x-ray source has been detected: source 1: ra (j2000.0): 22h 32m 34.33s dec (j2000.0): -22° 57' 01.0″ error: 3.7 arcsec (radius, 90% conf.) count-rate: (1.4 +/- 0.5)e-2 ct s^-1 distance: 3.2 arcmin from the ipn position flux: (4.1 +/- 1.4)e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) nevertheless, we note that at the xrt position the rass pspc 3 sigma upper limit is 0.05 cts/s (xrt equivalent count-rate). the uvot took images of 616s each on the three xrt tiles with the white filter 160-170 ks after the trigger. we identify one source at 1.9" from the xrt coordinates of source 1, with a white magnitude of 18.01. the uvot position is: ra (j2000) = 22:32:34.39 = 338.14330 (deg.) dec (j2000) = -22:57:02.7 = 22.95074 (deg.) with an estimated uncertainty of 0.5 arc sec. (radius, 90% confidence). however, we note that this is a known source in the dss and is therefore unlikely to be the afterglow. no other sources are detected to a limiting magnitude in the white filter of 20.8. more swift observations are planned in the next days to assess for variability 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/xrt_products/tiled_grb00104/<https://eur02.safelinks.protection.outlook.com/?url=https%3a%2f%2fwww.swift.ac.uk%2fxrt_products%2ftiled_grb00104%2f&data=05%7c01%7cvalerio.delia%40ssdc.asi.it%7cbbf1b046abbf47f102b008da29348927%7ccbfc58d4e60f468d8fe490676de085f7%7c0%7c0%7c637867602862749464%7cunknown%7ctwfpbgzsb3d8eyjwijoimc4wljawmdailcjqijoiv2lumziilcjbtii6ik1hawwilcjxvci6mn0%3d%7c3000%7c%7c%7c&sdata=rivavi0hbq7ov9vdq4k1xb1mbfcuxk9etljffe3p1ui%3d&reserved=0>. this circular is an official product of the swift team. | grb 220426a: swift-xrt and uvot observations |
the microchannel x-ray telescope (mxt) for the space-based multi-band astronomical variable objects monitor (svom), a franco-chinese mission (cnes/cnsa), is designed for the soft x-ray range (0.2-10 kev) to observe gamma-ray bursts (grbs) from the beginning to the afterglow emission. in the past years, the panter test facility has been testing the different mxt optics models. each optic is made up of an array of 5 x 5 micro pore optic (mpo) plates. we characterized the performance of the svom optic at different phases: bread-board (bb), qualification model (qm), flight model (fm), and flight spare (fs) for the optic followed by the performance model (pm) and flight model (fm) for the complete telescope fully integrated with the optic, detector, radiator and electronics. for the fm end-to-end test, in october 2021, the goal was to determine the half-energy width (hew) on-axis and off-axis, and to characterize the flight telescope's energy-dependent efficiency (effective area) under different thermal loads, i.e. different detector and optics temperatures. the final numbers will be presented in a paper in preparation. this paper provides the overview of various activities: setup, metrology and measurement, carried out at the panter facility during the development of the svom-mxt towards the end-to-end test. | svom-mxt optic and telescope testing at panter |
the em counterpart of gw170817 was remarkably different from model predictions. the gamma-rays were a factor of ~10^3 weaker than for regular short gamma-ray bursts (sgrbs), there was an early blue kilonova, and late radio/x-ray emission. a relativistic jet was launched and interacted with the merger ejecta, driving a wide-angled, mildly relativistic outflow, commonly referred to as a ``cocoon" or ``structured jet". afterglow observations primarily at radio and x-ray wavelengths revealed that the jet burrowed through the merger ejecta successfully. we will trigger our proposal on: one nearby (<100 mpc) ns-ns merger where the magnetar remnant probability is high or one ns-bh event. we request four epochs for follow-up. | chasing the x-ray afterglows of gravitational-wave events |
the detection of gamma-ray bursts (grbs) is one of the main scientific targets pursued by the magic collaboration since almost 20 years. the magic telescopes were specifically designed for this purpose: the main figures of merit are the fast slewing speed (7deg/s), the low energy threshold ( 50 gev at zenith) and the high sensitivity in the low energy regime. these features make magic one of the most suitable instrument for the follow-up and detection of grbs. after more than 15 years of dedicated searches, finally the first detection at teraelectronvolt energies of a grb, namely grb 190114c, was achieved by the magic collaboration, revealing a new emission component in the afterglow phase. this discovery opened up a new era in field of grb studies, which is now witnessing other detections, as demonstrated with the case of grb 201216c. furthermore, a hint of detection by magic from the short and nearby grb 160821b gives precious hints on the possible very high energy emission from this class of bursts, also in relation to searches of gravitation wave counterparts. therefore, magic is giving a crucial contribution to grb physics, leading to a better understanding of the mechanisms underlying these peculiar objects. in this contribution i will introduce the magic follow-up program, focusing on the aspects which led to the successful detection of grbs and highlighting some key results. finally, i will present the future challenges in these observations, discussing how magic can contribute even more to the field. | magic view of gamma-ray bursts at very high energies |
we suggest that the collision of a small solid body with a pulsar can lead to an observable glitch/anti-glitch. the glitch amplitude depends on the mass of the small body and the impact parameter as well. in the collision, a considerable amount of potential energy will be released either in the form of a short hard x-ray burst or as a relatively long-lasting soft x-ray afterglow. the connection between the glitch amplitude and the x-ray energetics can help to diagnose the nature of these timing anomalies. | collision-induced glitch/anti-glitches |
recently, jin et al. reanalyzed the optical observation data of grb 050709 and reported a line-like spectral energy distribution (sed) component observed by the very large telescope at t ∼ 2.5 days after the trigger of the burst, which had been interpreted as a broadened line signal arising from a macronova dominated by an iron group. in this work, we show that an optical flare origin of such a peculiar optical sed is still possible. interestingly, even in such a model, an “unusual” origin of the late-time long-lasting hubble space telescope f814w-band emission is still needed and a macronova/kilonova is the natural interpretation. | is the line-like optical afterglow sed of grb 050709 due to a flare? |
"we initiated observations with the chandra x-ray observatory of the short-duration grb 210726a (bernardini et al., gcn 30523; tohuvavohu, gcn 30535; palmer, gcn 30536) starting on 2021 july 29 16:04:38 ut, with a median observation time of ~3 days post-trigger. we obtained one acis-s observation under the proposal 22400461 (obsid 23445; pi: fong), with an effective exposure time of ~24.6 ks. we obtain a ~7sigma detection of grb 210726a with a total net source counts of 76+/-10 (0.5-7 kev). the chandra position of the short grb is fully consistent with the enhanced swift-xrt position (90% confidence; xrt grb catalogue, evans et al., 2009). the chandra position is: ra(j2000)= 12h53m09.7s dec(j2000)=19d11m24.6s with a total positional uncertainty of 0.81 arcsec (largely dominated by chandra's absolute astrometric uncertainty). based on our mcmc modeling, the xrt and chandra afterglow flux, starting at ~120.89 s post-burst, can be modeled with a broken power-law decline characterized by a second segment with a decay index (f~t^alpha) of alpha2=-0.62 (-0.05,+0.04) starting at ~418 s post-burst. in particular, the chandra detection roughly follows the latest decline rate based on xrt data alone.. further chandra observations are planned. we thank the chandra director, pat slane, and staff for the rapid planning and scheduling of these observations." | grb 210726a: chandra detection of the x-ray afterglow |
at 22:21:08 ut, the swift burst alert telescope (bat) triggered and located grb 210731a (trigger=1062336). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 300.314, -28.042 which is ra(j2000) = 20h 01m 15s dec(j2000) = -28d 02' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 40 sec. the peak count rate was ~1500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 22:24:29.4 ut, 200.9 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 300.3036, -28.0595 which is equivalent to: ra(j2000) = 20h 01m 12.86s dec(j2000) = -28d 03' 34.2" with an uncertainty of 5.8 arcseconds (radius, 90% containment). 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 7.96e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 63 seconds with the white filter starting 210 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 0.092. burst advocate for this burst is e. troja (eleonora.troja 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 210731a: swift detection of a burst |
x-ray afterglows from long-duration gamma ray bursts (grbs) are associated with energetic type ic supernovae and the late time behavior of the afterglow from all grbs follows the same universal normalization and power-law behavior at late times (~104 - 107 sec) when plotted relative to the time of the initial grb trigger. we describe constraints from this afterglow on the engine for grbs in the context of simple model for x-ray emission from accelerated relativistic electrons within an outgoing relativistic shock. we show that this universal scaling imposes 3 constraints: 1) the shock breakout energy is the same (~1051 ergs) for all bursts independently of the observed grb luminosity; 2) after breakout, the shock propagates through an optically thin low-density (~ 1 - 10 g cm-3 medium; 3) the energy radiated by the shock is a small fraction of the total shock energy. these suggest that the late-time power-law afterglow emission derives from the underlying energetic supernova with a similar total shock energy. the correlation of the of the observed grb energy with the luminosity of the plateau suggests a grb engine occurring at different radii within the expanding sn consistent with the induced gravitational collapse paradigm. work at the university of notre dame (gjm) supported by the u.s. department of energy under nuclear theory grant de-fg02-95-er40934. | constraints on the source for gamma-ray bursts from observed x-ray afterglows |
at 08:34:58 ut, the swift burst alert telescope (bat) triggered and located grb 180620a (trigger=843122). swift slewed to the burst with a 3 min delay. the bat on-board calculated location is ra, dec 279.883, +23.265, which is ra(j2000) = 18h 39m 32s dec(j2000) = +23d 15' 55" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows several overlapping peaks with a total duration of about 25 sec. the peak count rate was ~8000 counts/sec (15-350 kev), at ~12 sec after the trigger. the xrt began observing the field at 08:39:25.1 ut, 267.1 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 279.89575, 23.24373 which is equivalent to: ra(j2000) = 18h 39m 34.98s dec(j2000) = +23d 14' 37.4" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 87 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.60 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of nominal 150.000 seconds with the white filter starting 270 seconds after the bat trigger. there is a candidate afterglow in the list of sources generated on-board at ra(j2000) = 18:39:35.08 = 279.89618 dec(j2000) = +23:14:39.7 = 23.24437 with a 90%-confidence error radius of about 1.10 arc sec. this position is 1.7 arc sec. from the center of the xrt error circle. the estimated magnitude is 18.24. no correction has been made for the expected extinction corresponding to e(b-v) of 0.13. 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 180620a: swift detection of a burst with an optical counterpart |
swift-xrt has performed follow-up observations of the fermi/gbm-detected burst grb 230307a (dalessi et al. gcn circ. 33407) in a series of observations tiled on the sky. the total exposure time is 8.6 ks, distributed over 32 tiles; the maximum exposure at a single sky location was 1.6 ks. the data were collected between t0+76.4 ks and t0+100.9 ks, and are entirely in photon counting (pc) mode. two x-ray sources have been detected within the improved ipn error box (kozyrev et al., gcn circ. 33425), that has been fully covered by swift/xrt observations. source 2: ra (j2000): 04h 03m 26.24s = 60.85935° dec (j2000): -75° 22' 43.8″ = -75.3788° error: 3.4″ (radius, 90% conf., enhanced) count-rate: 0.019 (±0.004) ct s-1 distance: 36.6 arcsec from ipn position source 3: ra (j2000): 04h 03m 57.93s = 60.99137° dec (j2000): -75° 21' 26.8″ = -75.3574° error: 7.1″ (radius, 90% conf.) count-rate: 2.6 (+1.9, -1.3) ×10-3 ct s-1 distance: 175 arcsec from ipn position source 2 is below the rass limit and shows no definitive signs of fading. therefore, at the present time we cannot confirm this as the afterglow. source 3 is at a position consistent with a qso candidate (wu et al., 2023, raa, 23, 025006) and therefore is likely unrelated to grb 230307a. further observations are ongoing. 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_grb00110. this circular is an official product of the swift-xrt team. | grb 230307a: swift-xrt observations |
thunderstorms emit energetic radiation of different types, physically distinguishable based on duration. on the one hand, terrestrial gamma-ray flashes (tgfs) are microsecond-long bursts of photons, and on the other hand, gamma-ray glows last much longer, for seconds to minutes or even hours. whereas tgfs are the result of the developing lightning discharge, lightning is observed to terminate the usual gamma-ray glows. in the published work [1] we predict a new intermediate thunderstorm radiation mechanism, which we call a tgf afterglow, as it is caused by the capture of photonuclear neutrons produced by a tgf. tgf afterglows are milliseconds to seconds long; this duration is caused by the thermalization time of the intermediate neutrons. recently, the work of [2,3] experimentally confirmed this phenomenon, and [3] probably also detected the corresponding beta+ decay from the positron annihilation peak. although sometimes overlapping in duration, tgf afterglows are fundamentally different than gamma-ray glows. there may be gamma-ray observations from thunderstorms which are actually tgf afterglows. we have derived discriminators to search for tgf afterglows and we invite other researches to look for their signatures in their millisecond resolution gamma-ray measurements. references: [1] tgf afterglows: a new radiation mechanism from thunderstorms, c. rutjes, g. diniz, i.s. ferreira, u. ebert, geophys. res. lett. 44, 10702 - 10712 (2017), https://doi.org/10.1002/2017gl075552 [2] gamma ray signatures of neutrons from a terrestrial gamma ray flash, g.s. bowers et al., geophys. res. lett. 44, 10063 - 10070 (2017), https://doi.org/10.1002/2017gl075071 [3] photonuclear reactions triggered by lightning discharge, t. enoto et al. nature 551, 481-484 (23 november 2017), doi:10.1038/nature24630 | tgf afterglows: a new radiation mechanism from thunderstorms |
when a pair of neutron stars collide, they emit a fireworks show. could some of the low-energy light produced in these mergers be detectable years later? a team of scientists thinks so and theyre pretty sure theyve found an example.a rainbow of signalsin addition to gravitational waves, a slew of electromagnetic radiation is produced in the merger of two neutron stars, spanning the spectrum from gamma rays to radio waves.in 2017, the now-famous neutron star collision gw170817 gave us a first look at this expected emission: it revealed a short gamma-ray burst, infrared and optical light from ejecta in a kilonova, and relatively short-lived x-ray and radio afterglows caused by high-speed outflows.but theres one expected type of emission that was missing from gw170817, and its never before been spotted in any neutron star collision: radio flaring.illustration of radio emission from a neutron star merger. during the merger, some neutron star matter is flung outward. this ejecta interacts with the interstellar gas, producing a years-long radio flare. [lee et al. 2020]radio secrets revealedmodels of neutron star mergers predict that when ejecta are flung out from the stellar collision, theyll expand into space, eventually running into the surrounding medium of interstellar gas and dust. the subsequent interaction of the ejecta with the interstellar medium should produce radio flaring.the emission from these radio flares is expected to be quite long-lived lasting for years or even decades which means we could hope to find these signals long after the time of the explosion that produced them. but radio flares are also likely to be relatively faint, so we could only expect to spot flares from nearby collisions (within ~650 million light-years). additionally, only mergers that occur in environments with dense surrounding gas and dust will light up brightly enough for us to spot.with these constraints, its perhaps not surprising that we havent found any radio flares marking past mergers yet. but a team of scientists led by kyung-hwan lee (university of florida) recently waded through decades of radio data from the very large array and in a recent publication, theyre announcing that one transient may be the first identified radio flare from a stellar collision.a decades-old collisionobservational data for first j1419+3940 and best-fit radio light curves at three different frequencies. the data are better fit by the neutron-star-merger model (solid lines) than the long-gamma-ray-burst model (dashed lines). [lee et al. 2020]first j141918.9+394036 is a radio transient located in a dwarf galaxy 280 million light-years away. lee and collaborators compile survey data on this source spanning 23 years and evaluate possible explanations for the radio emission.while this source could potentially be explained as a long-gamma-ray-burst afterglow light from an off-axis jet produced by a collapsing star the radio data arent fit best by this picture. instead, the authors show via models that this transients light curve is best described as the decay of a radio flare, just as predicted from a neutron star merger. this means that first j141918.9+394036 likely marks a decades-old collision of two stars.within a few years, further observations of first j141918.9+394036 will allow us to better distinguish between models and confirm its nature. and as we find more signals like this one, we can use these observations to further understand the origin and physics of neutron star mergers potentially illuminating everything from the formation channel of binaries to the equation of state for neutron stars.citationfirst j1419+3940 as the first observed radio flare from a neutron star merger, k. h. lee et al 2020 apjl 902 l23. doi:10.3847/2041-8213/abbb8a | a radio flare from colliding stars? |
the multi-messenger discovery of the neutron star merger gw170817 showed that nearby mergers may be common. however, this merger probably would have not been identified as nearby without its gravitational wave detection, raising the possibility that other nearby events may be hiding in plain sight. a possibility to uncover such nearby mergers from the past to search for their radio emission that can last for decades. here we discuss the possibility that the radio transient first j1419+3940, first observed in 1993 and still detectable, could have originated from a neutron star merger. i will show that its observed radio light curve is well reproduced by a merger model with astrophysically expected parameters. i will discuss clues that could differentiate the transient's neutron star merger origin from the alternative explanation—the afterglow of an off-axis long gamma-ray burst. existing radio surveys likely already recorded multiple radio flares, informing us of the origin and properties of neutrons tar mergers and their role in the nucleosynthesis of the heaviest elements in the universe. | search for nearby neutron star mergers via radio flares |
a local population of faint short gamma-ray bursts (grbs) with late afterglow onset and bright optical kilonova was revealed by the discovery of the first binary neutron star merger gw170817/grb170817a. in our work we investigate whether similar nearby (<200 mpc) events were observed by nasa's neil gehrels swift observatory. 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 |
long-duration gamma-ray bursts (grbs) are a result of the collapse of massive stars accompanied by relativistic outflows. the initial gamma-ray flash of a grb is accompanied by a long-lasting afterglow visible from x-ray to radio wavelengths. the rate of radio afterglows detection is ∼ 30%. the early evolution of radio afterglows (below 4 ghz) is through the optically thick regime. therefore, the light curve peak corresponds to the transition from optically thick to the thin regime. hence, radio frequencies are unique in probing the evolution of the self-absorption frequency (ν_a) which in turn can constrain the physical parameters. due to the long-lived nature of radio afterglows, they serve as an excellent probe of grb energetics and their environments. in this work, i will present the results of our efforts in observing the radio afterglows of grbs at low frequencies with the giant meterwave radio telescope (gmrt). multi-wavelength numerical modeling performed by combining data at all available wavelengths has allowed us to put constraints on the ambient medium density, collimation angle, shock microphysical parameters, and kinetic energy of the burst. i will also highlight the importance of future sensitive radio telescopes which will increase the detection rate significantly and would be able to answer some of the important issues related to afterglow calorimetry, emission mechanisms, and environments around the massive stars exploding as grbs in the early universe. | radio afterglows of long duration gamma ray bursts |
we present the ixpe observation of grb 221009a which includes upper limits on the linear polarization degree of both prompt and afterglow emission in the soft x-ray energy band.grb 221009a is an exceptionally bright gamma-ray burst (grb) that reached earth on 2022 october 9 after traveling through the dust of the milky way. the imaging x-ray polarimetry explorer (ixpe) pointed at grb 221009a on october 11 observing, for the first time, the 2-8 kev x-ray polarization of a grb afterglow. additionally, ixpe captured halo-rings of dust-scattered photons which are echoes of the grb prompt emission, allowing for assessment on the prompt grb emission. in this presentation we report the results of the ixpe observation of grb 221009a. the imaging x ray polarimetry explorer (ixpe) is a joint us and italian mission. the us contribution is supported by the national aeronautics and space administration (nasa) and led and managed by its marshall space flight center (msfc), with industry partner ball aerospace (contract nnm15aa18c). the italian contribution is supported by the italian space agency (agenzia spaziale italiana, asi) through contract asi-ohbi-2017-12-i.0, agreements asi-inaf-2017-12-h0 and asi-infn-2017.13-h0, and its space science data center (ssdc) with agreements asi-inaf-2022-14-hh.0 and asi-infn 2021-43-hh.0, and by the istituto nazionale di astrofisica (inaf) and the istituto nazionale di fisica nucleare (infn) in italy. this research used data products provided by the ixpe team (msfc, ssdc, inaf, and infn) and distributed with additional software tools by the high-energy astrophysics science archive research center (heasarc), at nasa goddard space flight center (gsfc). | the ixpe view of grb 221009a |
at 23:25:42 ut, the swift burst alert telescope (bat) triggered and located grb 210217a (trigger=1033264). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 97.610, +68.715 which is ra(j2000) = 06h 30m 26s dec(j2000) = +68d 42' 53" 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 5 sec. the peak count rate was ~3400 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 23:27:20.1 ut, 97.8 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 97.58675, 68.72497 which is equivalent to: ra(j2000) = 06h 30m 20.82s dec(j2000) = +68d 43' 29.9" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 47 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 8.69 x 10^20 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 103 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 06:30:19.93 = 97.58305 dec(j2000) = +68:43:30.6 = 68.72516 with a 90%-confidence error radius of about 0.63 arc sec. this position is 6.2 arc sec. from the center of the xrt error circle. the estimated magnitude is 18.72 with a 1-sigma error of about 0.15. no correction has been made for the expected extinction corresponding to e(b-v) of 0.103. 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 210217a: swift detection of a burst with an optical counterpart |
at 23:21:33 ut, the swift burst alert telescope (bat) triggered and located grb 170607a (trigger=756284). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 7.343, +9.238 which is ra(j2000) = 00h 29m 22s dec(j2000) = +09d 14' 16" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single fred structure with a duration of about 40 sec. the peak count rate was ~4000 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 23:22:47.1 ut, 73.4 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 7.3655, 9.2425 which is equivalent to: ra(j2000) = +00h 29m 27.72s dec(j2000) = +09d 14' 33.0" with an uncertainty of 4.8 arcseconds (radius, 90% containment). this location is 81 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 5.32e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 83 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 00:29:27.80 = 7.36582 dec(j2000) = +09:14:36.2 = 9.24339 with a 90%-confidence error radius of about 0.61 arc sec. this position is 3.4 arc sec. from the center of the xrt error circle. the estimated magnitude is 15.90 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.04. burst advocate for this burst is a. d'ai (antonino.dai at ifc.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 170607a: swift detection of a burst with a bright optical counterpart |
at 16:39:07 ut, the swift burst alert telescope (bat) triggered and located grb 200324a (trigger=963260). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 222.685, +35.968 which is ra(j2000) = 14h 50m 44s dec(j2000) = +35d 58' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 60 sec. the peak count rate was ~1200 counts/sec (15-350 kev), at ~2 sec after the trigger. the xrt began observing the field at 16:42:11.8 ut, 183.9 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 222.67198, 35.94100 which is equivalent to: ra(j2000) = 14h 50m 41.28s dec(j2000) = +35d 56' 27.6" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 104 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.07 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.9 (+2.21/-1.93) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 1.27e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 194 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.01. this source lies within the current (sector 23) field-of-view of tess camera 2. 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 200324a: swift detection of a burst |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 200803a (cutini et al. gcn circ. 28203) in a series of observations tiled on the sky. the total exposure time is 3.5 ks, distributed over 4 tiles; the maximum exposure at a single sky location was 1.6 ks. the data were collected between t0+36.3 ks and t0+46.6 ks, and are entirely in photon counting (pc) mode. five uncatalogued x-ray sources are detected, of which one ("source 1") is above the rass limit, and is therefore likely the grb afterglow. using 812 s of pc mode data and 2 uvot images, we find an enhanced xrt position (using the xrt-uvot alignment and matching uvot field sources to the usno-b1 catalogue): ra, dec = 311.09390, -62.94478 which is equivalent to: ra (j2000): 20h 44m 22.54s dec(j2000): -62d 56' 41.2" with an uncertainty of 2.8 arcsec (radius, 90% confidence). this position is 9.7 arcmin from the fermi/lat position and 1.5 arcsec from the master optical counterpart reported by lipunov et al. (gcn circ. 28202). the light curve can be modelled with a power-law decay with a decay index of alpha=3.30 (+0.06, -2.56). if the light curve continues to decay with a power-law decay index of 3.30, the count rate at t+24 hours will be 2.1 x 10^-3 count s^-1 the results of the xrt-team automatic analysis of the likely afterglow are at https://www.swift.ac.uk/xrt_products/tiled_grb00092/source1.php. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00092. this circular is an official product of the swift-xrt team. | grb 200803a: swift-xrt afterglow detection |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 191016a (weikang zheng et al. gcn circ. 26012), collecting 4.2 ks of photon counting (pc) mode data between t0+45.0 ks and t0+56.9 ks. an uncatalogued x-ray source is detected consistent with being within 296 arcsec of the swift/bat position and is above the rass limit, and is therefore likely the grb afterglow. using 3470 s of pc mode data and 3 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 = 30.26933, +24.50988 which is equivalent to: ra (j2000): 02h 01m 04.64s dec(j2000): +24d 30' 35.6" with an uncertainty of 1.9 arcsec (radius, 90% confidence). this position is 93 arcsec from the swift/bat position. the light curve can be modelled with a power-law decay with a decay index of alpha=1.8 (+1.5, -0.5). a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+0.5, -0.4). the best-fitting absorption column is 1.4 (+1.7, -0.4) x 10^21 cm^-2, consistent with the galactic value of 1.0 x 10^21 cm^-2 (willingale et al. 2013). the counts to observed (unabsorbed) 0.3-10 kev flux conversion factor deduced from this spectrum is 3.4 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 1.4 (+1.7, -0.4) x 10^21 cm^-2 galactic foreground: 1.0 x 10^21 cm^-2 excess significance: <1.6 sigma photon index: 1.9 (+0.5, -0.4) the results of the xrt-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00929744. the results of the full analysis of the xrt observations are available at https://www.swift.ac.uk/too_grbs/00929744. this circular is an official product of the swift-xrt team. | grb 191016a: swift-xrt afterglow detection |
at 07:05:17 ut, the swift burst alert telescope (bat) triggered and located grb 200416a (trigger=966554). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 335.691, -7.530 which is ra(j2000) = 22h 22m 46s dec(j2000) = -07d 31' 47" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 10 sec. the peak count rate was ~3000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 07:06:57.1 ut, 99.9 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 335.69906, -7.51816 which is equivalent to: ra(j2000) = 22h 22m 47.77s dec(j2000) = -07d 31' 05.4" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 51 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 (6.54 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.2 (+3.00/-2.56) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 102 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 22:22:47.83 = 335.69929 dec(j2000) = -07:31:05.9 = -7.51831 with a 90%-confidence error radius of about 0.75 arc sec. this position is 1.1 arc sec. from the center of the xrt error circle. the estimated magnitude is 16.47 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.06. 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/) | grb 200416a: swift detection of a burst with an optical afterglow |
in order to investigate the true hosts and determine which matches are spurious, we have observed subsets of the sample with wht/acam, vlt/x-shooter, and atca. 7 targets were observed with acam/wht, 5 with vlt/x-shooter and 14 with atca a population of infrared-bright grb host galaxies has been identified by cross-matching x-ray afterglow positions to the allwise catalogue. selective cuts in apparent magnitude and catalogue quality flags, in addition to an fap analysis, yield 55 ir-sources that are convincingly associated with a grb x-ray position. (4 data files). | vizier online data catalog: ir-bright gamma-ray burst host galaxies (chrimes+, 2018) |
bat has triggered on a new grb 210402a (trigger #1040123) causing swift to slew to the location and make follow-up observations. due to a ground pass at the time of the grb, no precise trigger time, location, or light curve data is immediately available. these details will be given in a later circular. we note that fermi triggered on a grb at around the same time at a consistent location (fermi trigger #639093861) confirming its grb status. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 198.25866, 44.51291 which is equivalent to: ra(j2000) = 13h 13m 02.08s dec(j2000) = +44d 30' 46.5" with an uncertainty of 3.5 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 1.51 x 10^20 cm^-2 (willingale et al. 2013). the initial flux in the 2.5 s image was 1.31e-08 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of nominal 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 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. no correction has been made for the extinction in the milky way. 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 210402a: swift detection of a burst |
at 03:19:59 ut, the swift burst alert telescope (bat) triggered and located grb 200409a (trigger=965484). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 60.553, -50.247, which is ra(j2000) = 04h 02m 13s dec(j2000) = -50d 14' 49" 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 20 sec. the peak count rate was ~2000 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 03:21:13.1 ut, 73.4 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 60.53820, -50.22509 which is equivalent to: ra(j2000) = 04h 02m 09.17s dec(j2000) = -50d 13' 30.3" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 85 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 (1.27 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 5 (+4.06/-3.42) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 77 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 04:02:08.75 = 60.53646 dec(j2000) = -50:13:28.4 = -50.22455 with a 90%-confidence error radius of about 0.77 arc sec. this position is 4.6 arc sec. from the center of the xrt error circle. the estimated magnitude is 19.14 with a 1-sigma error of about 0.16. no correction has been made for the expected extinction corresponding to e(b-v) of 0.01. 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 200409a: swift detection of a burst with an optical counterpart |
swift-xrt has performed follow-up observations of the fermi/gbm-detected burst grb 230827b (gcn circ. 34584), collecting 3.6 ks of photon counting (pc) mode data between t0+231.3 ks and t0+249.7 ks. an uncatalogued x-ray source is detected consistent with being within 9.9 arcsec of the position of ztf23abaanxz/at2023qxj (gcn circ. 34574) and is believed to be the afterglow. using 3821 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 = 299.63944, +54.46318 which is equivalent to: ra (j2000): 19h 58m 33.47s dec(j2000): +54d 27' 47.5" with an uncertainty of 2.6 arcsec (radius, 90% confidence). this position is 0.8 arcsec from the ztf position. the light curve is consistent with a constant source of mean count rate 7.0e-02 ct/sec. a power-law fit gives an index of 2.490 (+0.015, -2.990). a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 1.59 (+0.33, -0.30). the best-fitting absorption column is 4.0 (+2.1, -1.0) x 10^21 cm^-2, consistent with the galactic value of 3.0 x 10^21 cm^-2 (willingale et al. 2013). the counts to observed (unabsorbed) 0.3-10 kev flux conversion factor deduced from this spectrum is 5.0 x 10^-11 (6.4 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 4.0 (+2.1, -1.0) x 10^21 cm^-2 galactic foreground: 3.0 x 10^21 cm^-2 excess significance: <1.6 sigma photon index: 1.59 (+0.33, -0.30) the results of the xrt-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021620. the results of the full analysis of the xrt observations are available at https://www.swift.ac.uk/too_grbs/00021620. this circular is an official product of the swift-xrt team. | grb 230827b: swift-xrt afterglow detection |
at 19:26:28 ut, the swift burst alert telescope (bat) triggered and located grb 200107b (trigger=948219). swift did not slew immediately due to an observing constraint. the bat on-board calculated location is ra, dec 107.066, -83.716 which is ra(j2000) = 07h 08m 16s dec(j2000) = -83d 42' 56" 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 ~1700 counts/sec (15-350 kev), at ~35 sec after the trigger. the xrt began observing the field at 19:41:27.6 ut, 899.0 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 106.92567, -83.7189 which is equivalent to: ra(j2000) = 07h 07m 42.16s dec(j2000) = -83d 43' 08.0" with an uncertainty of 21.3 arcseconds (radius, 90% containment). this location is 56 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.49 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 902 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 0.19. the "b" burst name is based on the fermi/gbm detection circular of this burst (gcn circ. 26659). 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 200107b: swift detection of a burst |
we have analysed 9.4 ks of photon counting (pc) mode xrt data for the swift-bat-detected burst grb 230116c (lien et al. gcn circ. 33193), collected between t0+159.6 ks and t0+537.9 ks. six 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): 223.47316 = 14:53:53.56 dec (j2000.0): -16.91649 = -16:54:59.4 error: 2.7 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0102 +/- 0.0013 ct s^-1 distance: 167 arcsec from swift-bat position. flux: (3.43 [+0.44, -0.43])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 223.4729 = 14:53:53.49 dec (j2000.0): -16.8864 = -16:53:11.2 error: 6.4 arcsec (radius, 90% conf.) count-rate: (2.80 [+1.09, -0.88])e-3 ct s^-1 distance: 65 arcsec from swift-bat position. source 3: ra (j2000.0): 223.4516 = 14:53:48.38 dec (j2000.0): -16.9158 = -16:54:56.8 error: 6.8 arcsec (radius, 90% conf.) count-rate: (3.15 [+0.84, -0.69])e-3 ct s^-1 distance: 165 arcsec from swift-bat position. flux: (1.45 [+0.39, -0.32])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 8: ra (j2000.0): 223.4602 = 14:53:50.44 dec (j2000.0): -16.8420 = -16:50:31.2 error: 6.3 arcsec (radius, 90% conf.) count-rate: (1.79 [+0.90, -0.70])e-3 ct s^-1 distance: 104 arcsec from swift-bat position. source 9: ra (j2000.0): 223.4090 = 14:53:38.16 dec (j2000.0): -16.9156 = -16:54:56.0 error: 8.1 arcsec (radius, 90% conf.) count-rate: (8.7 [+5.4, -4.3])e-4 ct s^-1 distance: 245 arcsec from swift-bat position. source 15: ra (j2000.0): 223.4391 = 14:53:45.37 dec (j2000.0): -16.8309 = -16:49:51.2 error: 8.7 arcsec (radius, 90% conf.) count-rate: (5.7 [+4.3, -3.4])e-4 ct s^-1 distance: 166 arcsec from swift-bat position. eleven 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/01149250. this circular is an official product of the swift-xrt team. | grb 230116c: swift-xrt observations |
the transient ztf20aazpphd (at2020jww) was reported by ahumada et al. (gcn 27737) at r = 19.6 +/- 0.05 within the localization region of the short grb200514b (trigger 611140062) detected by the gamma-ray burst monitor (gbm) on the fermi satellite at mjd = 58983.38029 (gcn 27736). atlas, the twin telescope system on haleakala and mauna loa was observing this region of sky in normal sky operations (tonry et al. 2018, pasp, 130f4505, smith et al. 2020, arxiv:2003.09052). we detect ztf20aazpphd before the ztf epoch at the following magnitudes : atlas c-band : mjd dt m err 58983.42278 +1.02 19.47 0.13 58983.42461 +1.06 19.18 0.20 58983.43478 +1.31 19.46 0.13 58983.43890 +1.41 19.42 0.21 where dt is the time in hrs since fermi trigger. ztf reported the r-band : 58983.49 +2.63 19.6 0.05 the first atlas detection is 1.61hrs before the ztf in the cyan-band (a composite g+r filter). the two magnitudes are consistent, given the errors and the different filter profiles. therefore there is no evidence of any rapid decline within this short interval, as might be expected for a sgrb afterglow. we also have non-detections of ztf20aazpphd 2 days before, hence it is more likely a young supernova. | grb200514b: atlas detections of ztf20aazpphd |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 230512a in a series of observations tiled on the sky. the total exposure time is 4.9 ks, distributed over 4 tiles; the maximum exposure at a single sky location was 2.3 ks. the data were collected between t0+45.5 ks and t0+57.3 ks, and are entirely in photon counting (pc) mode. nine 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): 295.4803 = 19:41:55.26 dec (j2000.0): +38.6649 = +38:39:53.6 error: 4.2 arcsec (radius, 90% conf. [enhanced position]) count-rate: (8.8 [+3.9, -3.0])e-3 ct s^-1 distance: 980 arcsec from fermi/lat position. flux: (5.1 [+2.2, -1.8])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 3: ra (j2000.0): 295.5430 = 19:42:10.33 dec (j2000.0): +38.7526 = +38:45:09.4 error: 5.5 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0176 [+0.0056, -0.0047] ct s^-1 distance: 1331 arcsec from fermi/lat position. flux: (3.57 [+1.13, -0.95])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 5: ra (j2000.0): 295.2060 = 19:40:49.43 dec (j2000.0): +38.4686 = +38:28:07.1 error: 6.2 arcsec (radius, 90% conf.) count-rate: 0.0105 [+0.0042, -0.0034] ct s^-1 distance: 600 arcsec from fermi/lat position. source 6: ra (j2000.0): 295.7616 = 19:43:2.79 dec (j2000.0): +38.3644 = +38:21:51.9 error: 3.9 arcsec (radius, 90% conf. [enhanced position]) count-rate: (6.7 [+3.5, -2.6])e-3 ct s^-1 distance: 1028 arcsec from fermi/lat position. source 7: ra (j2000.0): 295.0895 = 19:40:21.48 dec (j2000.0): +38.4348 = +38:26:05.5 error: 6.8 arcsec (radius, 90% conf.) count-rate: (5.4 [+3.3, -2.4])e-3 ct s^-1 distance: 884 arcsec from fermi/lat position. source 8: ra (j2000.0): 295.3130 = 19:41:15.11 dec (j2000.0): +38.4565 = +38:27:23.3 error: 5.1 arcsec (radius, 90% conf. [enhanced position]) count-rate: (8.7 [+4.1, -3.2])e-3 ct s^-1 distance: 318 arcsec from fermi/lat position. source 9: ra (j2000.0): 295.2484 = 19:40:59.62 dec (j2000.0): +38.1016 = +38:06:05.7 error: 7.7 arcsec (radius, 90% conf.) count-rate: (5.5 [+3.1, -2.3])e-3 ct s^-1 distance: 1156 arcsec from fermi/lat position. source 10: ra (j2000.0): 295.1589 = 19:40:38.13 dec (j2000.0): +38.4685 = +38:28:06.6 error: 6.1 arcsec (radius, 90% conf.) count-rate: (9.8 [+5.8, -4.3])e-3 ct s^-1 distance: 723 arcsec from fermi/lat position. source 11: ra (j2000.0): 295.2125 = 19:40:50.99 dec (j2000.0): +38.0868 = +38:05:12.5 error: 4.5 arcsec (radius, 90% conf. [enhanced position]) count-rate: (9.5 [+4.1, -3.2])e-3 ct s^-1 distance: 1245 arcsec from fermi/lat position. flux: (3.3 [+1.4, -1.1])e-13 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 https://www.swift.ac.uk/xrt_products/tiled_grb00111. this circular is an official product of the swift-xrt team. | grb 230512a: swift-xrt observations |
we report the discovery of the fast optical transient ztf20abtxwfx/at2020sev with the zwicky transient facility (ztf, bellm et al. 2019, graham et al. 2019) at coordinates: raj2000 = 16:41:21.21 (250.338384d) decj2000 = +57:08:20.5 (+57.139027d) ztf20abtxwfx was found during the science validation of the new "ztf realtime search and triggering" (ztf-rest) project. ztf-rest will aim at near real-time identification of kilonova candidates in ztf data using the methods described in andreoni et al. (2020d), independently of gravitational-wave or gamma-ray triggers. ztf20abtxwfx was first detected on 2020-08-18 05:20 ut, heareafter labelled t_det. ztf20abtxwfx faded by ~1.3 mag in r-band in the first 2 days since t_det. the transient was last detected on 2020-08-23 04:51 ut at r = 20.98 +- 0.24 mag. stringent upper limits constrain the transient onset time to be within ~1 day from t_det. the color of the transient appears to be red, with g-r~0.1 and g-i~0.3 one day after t_det. the galactic extinction on the line of sight is low, with e(b-v)=0.015 mag (planck collaboration et al., 2015). in the table below, we report forced photometry obtained with forcephotztf (yao et al., 2019) on images processed in real-time through the ztf reduction and image subtraction pipelines at ipac (masci et al. 2019). -----------------+--------+------+------ date (ut) | mag | emag | band -----------------+--------+------+------ 2020-08-17 06:45 | > 21.0 | | r 2020-08-18 05:20 | 19.22 | 0.04 | r 2020-08-19 04:19 | 20.03 | 0.11 | r 2020-08-19 05:23 | 20.16 | 0.09 | g 2020-08-19 05:53 | 19.83 | 0.14 | i 2020-08-20 04:47 | 20.54 | 0.15 | r 2020-08-20 05:46 | 20.66 | 0.16 | g 2020-08-21 04:25 | 20.71 | 0.17 | r 2020-08-21 06:54 | > 20.8 | | g 2020-08-23 04:12 | > 21.0 | | g 2020-08-23 04:51 | 20.98 | 0.24 | r 2020-08-24 04:26 | > 20.5 | | r -----------------+--------+------+------ ztf20abtxwfx is located at high galactic latitude b_gal = 40.0 deg. deep legacy survey, pan-starrs1, and cfht images of the field do not reveal any permanent source at the transient location. the spatially closest source reported in the legacy survey dr8 catalog (ra, dec = 250.3368d, 57.1377d) has a separation of 5.7 arcsec from ztf20abtxwfx, is extended (not point-like), has photometric redshift of z = 0.73 +- 0.2, and has reported magnitudes of g=23.37 mag, r=22.63 mag, and z=21.86 mag. we searched the gcn archives, the fermi gbm catalog, the fermi gbm subthreshold catalog, and the konus-wind triggered and waiting mode data for any possible gamma-ray burst (grb) counterpart. we found one possible counterpart, grb 200817a (fermi gbm team, gcn #28254). the trigger time of grb 200817a was on 2020-08-17 09:25:20 ut, which lies in the time interval between our last optical non-detection and t_det. ztf20abtxwfx is located in the 93rd percentile of the localization region, at an angular distance of about 32 degrees from the central grb position. we confirm that the position of ztf20abtxwfx was within the gbm field-of-view at the time of the grb. multi-wavelength follow-up of ztf20abtxwfx is encouraged. ztf and growth are worldwide collaborations comprising caltech, usa; ipac, usa, wis, israel; okc, sweden; jsi/umd, usa; u washington, usa; desy, germany; most, taiwan; uw milwaukee, usa; lanl usa; tokyo tech, japan; iitb, india; iia, india; ljmu, uk; ttu, usa; sdsu, usa and usyd, australia. ztf acknowledges the generous support of the nsf under ast msip grant no 1440341. growth acknowledges generous support of the nsf under pire grant no 1545949. alert distribution service provided by dirac@uw (patterson et al. 2019). alert database searches are done with kowalski (duev et al. 2019). | zwicky transient facility discovery of ztf20abtxwfx/at2020sev, a fast optical transient and candidate afterglow |
gamma ray bursts (grbs) can be used as a powerful tool to study galactic environments at different epochs of the universe's evolution, thanks to their bright afterglow emission ranging from x-rays to optical and radio wavebands. important aspect of the environment is dust, which plays a central role in the astrophysical processes of interstellar medium and in the formation of stars. grbs can be a unique probe of dust at cosmological distances, where its origin and properties are still poorly known. by using a sample of grb afterglow spectra observed with the vlt/x-shooter spectrograph we studied the rest-frame extinction in grb lines-of-sight by modelling the broadband near-infrared to x-ray afterglow spectral energy distributions. we present our results on the rest-frame extinction of our sample, and illustrate that the spectroscopic data, thanks to a combination of excellent resolution and coverage of the blue part of the spectral energy distributions, are more successful than photometric measurements in constraining the extinction curves and therefore the dust properties in grb hosts. | extinction curves of grb environment with the x-shooter |
at 01:07:44 ut, the swift burst alert telescope (bat) triggered and located grb 201027a (trigger=1002158). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 155.974, -5.515 which is ra(j2000) = 10h 23m 54s dec(j2000) = -05d 30' 53" 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 ~1500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 01:09:07.5 ut, 83.4 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 155.9700, -5.5101 which is equivalent to: ra(j2000) = 10h 23m 52.81s dec(j2000) = -05d 30' 36.2" with an uncertainty of 2.3 arcseconds (radius, 90% containment). this location is 22 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (4.67 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 2.6 (+2.14/-1.93) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 86 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 201027a: swift detection of a burst |
fermi-gbm triggered grb 200412b (gcncs 27547, 27548i, 27558) prompt emissions and high energy observations were also carried out by fermi-lat (gcnc 27557) and other space-based facilities like konus-wind (gcnc 27581), astrosat (gcnc 27563), calet (gcnc 27572) and hxmt (gcnc 27567). categorised as a long-duration grb, swift-xrt triggered and found a x-ray afterglow counterpart (gcnc 27561, 27600) decaying typical to those seen in case of other long duration bursts at the epoch of observations. our joint spectral analysis of the combined fermi gbm-lat data yields e_peak ~ 250 +/- 18 kev and spectral slope \beta ~ -2.8 +/- 0.4 above 100 mev, similar to those reported in gcnc 27558 and gcnc 27581. once used with the empirical amati relation, the estimated value of the e_peak and the observed fluence values (gcnc 27558, gcnc 27581) place a constrain of the redshift to be 0.3 < z < 1.5 for grb 200412b. the optical counterpart of the gagarin-day burst was discovered by master group of telescopes (gcnc 27555, 27556) and follow-up observations were continued by several ground-based facilities (gcncs 27564, 27566, 27567, 27567, 27570, 27571, 27574, 27575, 27576, 27583, 27593, 27598, 27604, 27605 and 27610). late time follow-up observations of the optical counterpart were initiated using the 4kx4k ccd imager (pandey et al. 2017, arxiv:1711.05422v1) mounted at the axial port of the 3.6m devasthal optical telescope of aries nainital starting on 15th april and continued till 25th april 2020. multiple frames having exposure times of 360s each were taken in various broad-band filters including ic, rc and g-bands. a fading afterglow candidate was clearly seen in single as well as in stacked frames decayed around ~ 3 mag during our observing run. we report following preliminary brightness of the optical afterglow seen in our stacked frames calibrated against unsob1 and panstarrs nearby stars. start time, 23 april 20.61 ut, 360*12, rc, 24.62+/-0.12, seeing ~ 0.8 arcsec start time, 24 april 19.71 ut, 360*10, g, 25.21+/-0.10, seeing ~ 0.9 arcsec once clubbed along with published gcnc values in r-band, our late time observations indicate towards a power-law decay nature of the afterglow as seen in case of other well-monitored afterglows. the temporal decay index between one day to the epoch of our observations demand a power-law temporal flux-decay index of ~ 1.78+-0.15. this temporal decay is similar to those seen at xrt frequencies and might indicate towards possible early time jet-break, if any. it is also to be cautioned that possible underlying host galaxy contamination to our late time rc-band stacked frames can not be ruled out. detailed analysis of the data is ongoing. to decipher about late time nature of the temporal decay of the afterglow and to detect the host galaxy or possible underlying supernova, observations using bigger optical-nir facilities are encouraged. this circular may be cited. 3.6m devasthal optical telescope (dot) is a recently commissioned facility in northern himalayan region of india (long:79 41 04e, lat:29 21 40n, alt:2540m) owned and operated by the aryabhatta research institute of observational sciences (aries), nainital (https://www.aries.res.in). authors of this gcn circular thankfully acknowledge consistent support from the staff members to run and maintain the 3.6m dot and specially to director aries to make these observations possible during the ongoing covid19 triggered lock-down phase. | gagarin-day grb 200412b: observations with the 3.6m devasthal optical telescope |
swift-xrt has performed follow-up observations of the maxi-detected burst grb 210102b (guo et al. gcn circ. 29223) in a series of observations tiled on the sky. the total exposure time is 1.3 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 406 s. the data were collected between t0+19.7 ks and t0+26.0 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): 353.8173 = 23:35:16.14 dec (j2000.0): -21.0821 = -21:04:55.6 error: 5.5 arcsec (radius, 90% conf.) count-rate: 0.030 [+0.016, -0.012] ct s^-1 distance: 1289 arcsec from maxi position. the results of the xrt-team automatic analysis of the tiled xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/tiled_grb00097. this circular is an official product of the swift-xrt team. | grb 210102b: swift-xrt observations |
swift-xrt has performed follow-up observations of the swift/bat-detected burst grb 201128b (james delaunay et al. gcn circ. 28971), collecting 5.0 ks of photon counting (pc) mode data between t0+246.0 ks and t0+303.8 ks. ten 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): 339.4164 = 22:37:39.94 dec (j2000.0): -49.2698 = -49:16:11.1 error: 5.1 arcsec (radius, 90% conf.) count-rate: (3.32 [+1.13, -0.93])e-3 ct s^-1 distance: 169 arcsec from swift/bat position. flux: (1.67 [+0.57, -0.47])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 339.0250 = 22:36:5.99 dec (j2000.0): -49.1319 = -49:07:54.7 error: 5.2 arcsec (radius, 90% conf.) count-rate: (4.7 [+2.8, -2.0])e-3 ct s^-1 distance: 876 arcsec from swift/bat position. source 4: ra (j2000.0): 339.5648 = 22:38:15.55 dec (j2000.0): -49.2141 = -49:12:50.9 error: 7.7 arcsec (radius, 90% conf.) count-rate: (2.35 [+1.05, -0.81])e-3 ct s^-1 distance: 508 arcsec from swift/bat position. flux: (7.8 [+3.5, -2.7])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 5: ra (j2000.0): 339.4267 = 22:37:42.42 dec (j2000.0): -49.1173 = -49:07:02.2 error: 5.3 arcsec (radius, 90% conf.) count-rate: (1.36 [+0.77, -0.57])e-3 ct s^-1 distance: 494 arcsec from swift/bat position. flux: (9.5 [+5.4, -4.0])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 6: ra (j2000.0): 339.2905 = 22:37:9.71 dec (j2000.0): -49.3858 = -49:23:08.7 error: 5.1 arcsec (radius, 90% conf.) count-rate: (6.6 [+2.0, -1.6])e-3 ct s^-1 distance: 524 arcsec from swift/bat position. flux: (1.69 [+0.50, -0.42])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 7: ra (j2000.0): 339.2768 = 22:37:6.43 dec (j2000.0): -49.1392 = -49:08:21.0 error: 4.9 arcsec (radius, 90% conf.) count-rate: (4.7 +/- 1.3)e-3 ct s^-1 distance: 425 arcsec from swift/bat position. flux: (2.03 +/- 0.55)e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 8: ra (j2000.0): 339.2888 = 22:37:9.31 dec (j2000.0): -49.1961 = -49:11:45.9 error: 7.2 arcsec (radius, 90% conf.) count-rate: (2.17 [+0.97, -0.77])e-3 ct s^-1 distance: 236 arcsec from swift/bat position. flux: (1.84 [+0.83, -0.65])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 9: ra (j2000.0): 339.2747 = 22:37:5.92 dec (j2000.0): -49.1221 = -49:07:19.5 error: 9.8 arcsec (radius, 90% conf. [enhanced position]) count-rate: (3.04 [+1.19, -0.95])e-3 ct s^-1 distance: 483 arcsec from swift/bat position. flux: (7.4 [+2.9, -2.3])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 10: ra (j2000.0): 339.5188 = 22:38:4.51 dec (j2000.0): -49.1801 = -49:10:48.4 error: 6.9 arcsec (radius, 90% conf.) count-rate: (1.89 [+0.94, -0.72])e-3 ct s^-1 distance: 454 arcsec from swift/bat position. flux: (3.0 [+1.5, -1.1])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 11: ra (j2000.0): 339.5043 = 22:38:1.04 dec (j2000.0): -49.3084 = -49:18:30.2 error: 5.2 arcsec (radius, 90% conf.) count-rate: (2.14 [+1.07, -0.81])e-3 ct s^-1 distance: 418 arcsec from swift/bat position. flux: (1.04 [+0.52, -0.39])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) a catalogued source was also detected. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021044. this circular is an official product of the swift-xrt team. | grb 201128b: swift-xrt observations |
swift-xrt has performed follow-up observations of the fermi-detected burst grb 200325b (fermi gbm team, gcn cir. 27441), collecting 1.1 ks of photon counting (pc) mode data between t0+102.4 ks and t0+124.8 ks in a single pointing covering the region of the candidate grb optical counterpart initially reported by lipunov et al. (gcn circ. 27446). an uncatalogued x-ray source has been detected: source 1: ra (j2000.0): 167.55381 = 11:10:12.91 dec (j2000.0): +27.8196 = +27:49:10.5 error: 4.9 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.020 [+/-0.005] ct s^-1 flux: (7.2 [+/-1.8])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) the source is below the rass limit and, due to the limited amount of data available so far, shows no signs of fading. the position of this source is consistent with the one reported for the grb optical afterglow (lipunov et al., gcn circ. 27446; pozanenko et al., gcn circ. 27452; belkin et al., gcn circ. 27455; strausbaugh & cucchiara, gcn circ. 27456). we therefore conclude that this is the x-ray afterglow of grb 200325b. 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/00020978 <https://www.swift.ac.uk/too_grbs/00020978>. the swift/uvot began settled observations of the field of grb 200325b 102ks after the fermi/gbm trigger. an optical source consistent with the grb optical afterglow (lipunov et al., gcn circ. 27446; pozanenko et al., gcn circ. 27452; belkin et al., gcn circ. 27455; strausbaugh & cucchiara, gcn circ. 27456) is detected in the initial uvot white exposure. a preliminary magnitude in white using the uvot photometric system (breeveld et al. 2011, aip conf. proc. 1358, 373) is: filter t_start(ks) t_stop(ks) exp(s) mag white 102.39 124.75 1044 21.27 ± 0.24 this magnitude is not corrected for the galactic extinction due to the reddening of e(b-v) = 0.03 in the direction of the burst (schlegel et al. 1998). | grb 200325b: swift-xrt and uvot observations |
at 23:06:34 ut, the swift burst alert telescope (bat) triggered and located grb 201221d (trigger=1014037). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 171.049, +42.144 which is ra(j2000) = 11h 24m 12s dec(j2000) = +42d 08' 39" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single-peaked structure with a duration of about 0.3 sec. the peak count rate was ~9000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 23:08:01.7 ut, 87.4 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 171.05873, 42.14332 which is equivalent to: ra(j2000) = 11h 24m 14.10s dec(j2000) = +42d 08' 36.0" with an uncertainty of 5.7 arcseconds (radius, 90% containment). this location is 26 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 92 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. burst advocate for this burst is 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 201221d: swift detection of a bright short burst |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 201116a (axelsson et al. gcn circ. 28907) in a series of observations tiled on the sky. the total exposure time is 4.8 ks, distributed over 3 tiles; the maximum exposure at a single sky location was 3.1 ks. the data were collected between t0+46.5 ks and t0+62.3 ks, and are entirely in photon counting (pc) mode. four uncatalogued x-ray sources are detected, of which one ("source 3") is above the rass 3-sigma upper limit at this position, and shows signes of fading, and is therefore likely the grb afterglow. using 2405 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 = 149.32493, +0.27586 which is equivalent to: ra (j2000): 09h 57m 17.98s dec(j2000): +00d 16' 33.1" with an uncertainty of 2.5 arcsec (radius, 90% confidence). this position is 2.4 arcmin from the fermi/lat position. as already reported by de ugarte postigo et al (gcn circ. 28915), there is an optical afterglow counterpart consistent with this x-ray object. the light curve is consistent with a constant source of mean count rate 5.2e-02 ct/sec, however fading also cannot be ruled out. a power-law fit gives an index of 1.6 (+1.4, -2.0), thus the large uncertainties hinder a confident statement about fading. a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 1.9 (+0.6, -0.5). the best-fitting absorption column is 2.7 (+2.5, -1.9) x 10^21 cm^-2, in excess of the galactic value of 2.8 x 10^20 cm^-2 (willingale et al. 2013). the counts to observed (unabsorbed) 0.3-10 kev flux conversion factor deduced from this spectrum is 3.2 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 2.7 (+2.5, -1.9) x 10^21 cm^-2 galactic foreground: 2.8 x 10^20 cm^-2 excess significance: 2.1 sigma photon index: 1.9 (+0.6, -0.5) the results of the xrt-team automatic analysis of the afterglow are at: https://www.swift.ac.uk/xrt_products/00021040. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00095. this circular is an official product of the swift-xrt team. | grb 201116a: swift-xrt afterglow detection |
at 17:22:56 ut, the swift burst alert telescope (bat) triggered and located grb 230903a (trigger=1189514). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 9.926, -40.924 which is ra(j2000) = 00h 39m 42s dec(j2000) = -40d 55' 25" 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 ~1500 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 17:24:47.9 ut, 111.7 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 9.91169, -40.94930 which is equivalent to: ra(j2000) = 00h 39m 38.81s dec(j2000) = -40d 56' 57.5" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 99 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 (2.68 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 2.6 (+2.17/-1.93) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 250 seconds with the u filter starting 117 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.2 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. 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 230903a: swift detection of a burst |
at 19:19:03 ut, the swift burst alert telescope (bat) triggered and located grb 210726a (trigger=1061687). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 193.342, +19.185 which is ra(j2000) = 12h 53m 22s dec(j2000) = +19d 11' 05" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a short spike with a tail with a total duration of about ~3 sec. the peak count rate was ~1500 counts/sec (15-350 kev), at ~0 sec after the trigger. this may be a short grb. the xrt began observing the field at 19:20:03.6 ut, 60.0 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 193.2909, 19.1898 which is equivalent to: ra(j2000) = 12h 53m 09.81s dec(j2000) = +19d 11' 23.2" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 174 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 (1.73 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.4 (+2.93/-2.51) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 250 seconds with the u filter starting 276 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 18.0 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.020. 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 210726a: swift detection of a burst |
we propose to continue our previous commensal transients project that has so far resulted in the best limits yet on radio transient rates (rowlinson et al. 2016). many types of variable and transient sources are predicted and observed at low frequencies. for example, flares from low-mass stars and brown dwarfs, magnetars, and flares associated with state transitions in accreting stellar-mass and intermediate-mass black holes. in addition, possible non-repeating transient sources, such as merging black holes and tidal disruption events, are expected to emit at mwa frequencies. the mwa is extremely well-suited for blind transient surveys due to its large instantaneous field of view and high sensitivity. we propose to continue our survey of transient and variable sources in the eor (epoch of reionisation) fields. this is a commensal project, sharing data with the eor collaboration and targets transient events on time scales from 30 seconds to years, enabling us to search for both short duration coherent emission (e.g. fast radio bursts, frbs) and long duration incoherent sources (e.g. gamma-ray burst, grb, afterglows). | search for variable and transient sources in the eor fields with the mwa |
in this contribution, we demonstrate astro-h's capability to measure the chemical evolution in the high-z ( z < 3 ) universe by observing x-ray afterglows of gamma-ray bursts (grbs) and distant blazars. utilizing these sources as background light sources, the excellent energy resolution of astro-h/sxs allows us to detect emission and absorption features from heavy elements in the circumstellar material in the host galaxies, from the intergalactic medium (igm) and in the ejecta of grb explosions. in particular, we can constrain the existence of the warm-hot intergalactic medium (whim), thought to contain most of the baryons at redshift of z < 3, with a typical exposure of one day for a follow-up observation of a grb afterglow or 300 ks exposure for several distant blazars. in addition to the chemical evolution study, the combination of the sgd, hxi, sxi and sxs will measure, for the first time, the temporal behavior of the spectral continuum of grb afterglows and blazars over a broad energy range and short time scales allowing detailed modeling of jets. the ability to obtain these data from grb afterglows will depend critically on the availability of grb triggers and the capability of astro-h to respond rapidly to targets of opportunity. at the present time it seems as if swift will still be functioning normally during the first two years of astro-h operations providing the needed triggering capability. | future astro-h observations of chemical evolution in high-z universe |
swift-xrt has performed follow-up observations of the integral-detected burst grb 200715a (mereghetti et al. gcn circ. 28110), collecting 3.3 ks of photon counting (pc) mode data between t0+7.5 ks and t0+26.2 ks. an uncatalogued x-ray source is detected consistent with being within 266 arcsec of the integral position and is above the rass limit, and is therefore likely the grb afterglow. the position of this source is ra, dec=248.5377, -51.8356 which is equivalent to: ra (j2000): 16:34:9.04 dec(j2000): -51:50:08.0 with an uncertainty of 3.7 arcsec (radius, 90% confidence). this position is 13 arcsec from the integral position (mereghetti et al. gcn circ. 28110). the light curve can be modelled with a power-law decay with a decay index of alpha=1.06 (+0.32, -0.27). a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 2.1 (+/-0.5). the best-fitting absorption column is 1.06 (+0.60, -0.29) x 10^22 cm^-2, consistent with the galactic value of 7.6 x 10^21 cm^-2 (willingale et al. 2013). the counts to observed (unabsorbed) 0.3-10 kev flux conversion factor deduced from this spectrum is 4.8 x 10^-11 (9.4 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 1.06 (+0.60, -0.29) x 10^22 cm^-2 galactic foreground: 7.6 x 10^21 cm^-2 excess significance: <1.6 sigma photon index: 2.1 (+/-0.5) if the light curve continues to decay with a power-law decay index of 1.06, the count rate at t+24 hours will be 6.2 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 kev flux of 3.0 x 10^-13 (5.8 x 10^-13) erg cm^-2 s^-1. the results of the xrt-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021018. the results of the full analysis of the xrt observations are available at https://www.swift.ac.uk/too_grbs/00021018. this circular is an official product of the swift-xrt team. | grb 200715a: swift-xrt afterglow detection |
at 10:27:23 ut, the swift burst alert telescope (bat) triggered and located grb 200528a (trigger=974827). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 176.637, +58.147 which is ra(j2000) = 11h 46m 33s dec(j2000) = +58d 08' 50" 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 60 sec. the peak count rate was ~19000 counts/sec (15-350 kev), at ~33 sec after the trigger. the xrt began observing the field at 10:28:33.9 ut, 70.2 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 176.6438, 58.1921 which is equivalent to: ra(j2000) = 11h 46m 34.51s dec(j2000) = +58d 11' 31.6" with an uncertainty of 5.2 arcseconds (radius, 90% containment). this location is 162 arcseconds from the bat onboard position, within the bat error circle. no event data are yet available to determine the column density using x-ray spectroscopy. the initial flux in the 0.1 s image was 4.08e-08 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 80 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.01. burst advocate for this burst is 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 200528a: swift detection of a burst |
we observed the field of grb 200729a (evans et al., gcn 28165) with the nordic optical telescope equipped with the alfosc imager. observations were carried out in the r and z filters, and started on 2020 jul 29.911 ut (2.2 hr after the trigger), as soon as visibility allowed. within the xrt position of the candidate afterglow (osborne et al., gcn 28168), we detect no new sources compared to archival pan-starrs images. the 3-sigma limiting magnitudes are: r > 22.5 ab z > 22.0 ab as noted by evans et al. (gcn 28165), the location of the x-ray source lies on top of the nearby galaxy ngc 4242, whose distance is ~5.5 mpc (from simbad, which however presents values up to 10 mpc). we note that, if the grb is associated with ngc 4242, our limit would correspond to an absolute magnitude m_r > -6.2, which, in lack of significant extinction, provides a deep limit to the grb optical luminosity. for example, the earliest detection of sn 2008d (3.5 hr after the outburst; soderberg et al. 2008, nat, 453, 469) had an absolute u-band magnitude m(u) = -12.3 (even before correcting for the significant extinction). at 5.5 mpc, the gamma-ray fluence of 8*10^-7 erg cm^-2 (taken from https://gcn.gsfc.nasa.gov/notices_s/984929/ba/) would correspond to 3*10^45 erg - fainter than the low-luminosity events grb 980425, grb 170817a, and the x-ray output of sn 2008d. while the visibility of this target from la palma is now over, we encourage further observations from other locations. | grb 200729a: not optical upper limits |
at 20:19:50 ut, the swift burst alert telescope (bat) triggered and located grb 201029a (trigger=1003002). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 229.601, +44.464 which is ra(j2000) = 15h 18m 24s dec(j2000) = +44d 27' 50" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single complex peak structure with a duration of about 40 sec. the peak count rate was ~1800 counts/sec (15-350 kev), at ~5 sec after the trigger. the xrt began observing the field at 20:21:52.3 ut, 122.3 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 229.58280, 44.45975 which is equivalent to: ra(j2000) = 15h 18m 19.87s dec(j2000) = +44d 27' 35.1" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 49 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 7.42e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 131 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. burst advocate for this burst is 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 201029a: swift detection of a burst |
swift-xrt has performed follow-up observations of the integral-detected burst grb 201214a (mereghetti et al. gcn circ. 29037), collecting 4.1 ks of photon counting (pc) mode data between t0+5.2 ks and t0+23.6 ks. one uncatalogued x-ray source has been detected consistent with being within 246 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 2: ra (j2000.0): 170.92446 = 11:23:41.87 dec (j2000.0): +33.86930 = +33:52:09.5 error: 2.2 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0182 +/- 0.0024 ct s^-1 distance: 36 arcsec from integral position. flux: (4.48 +/- 0.60)e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) three uncatalogued sources were also detected too far from the grb position to be likely afterglow candidates. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021406. this circular is an official product of the swift-xrt team. | grb 201214a: swift-xrt observations |
at 22:50:39 ut, the swift burst alert telescope (bat) triggered and located grb 200306c (trigger=960102). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 198.582, +11.255 which is ra(j2000) = 13h 14m 20s dec(j2000) = +11d 15' 18" 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 ~1800 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 22:52:35.9 ut, 116.9 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 198.55562, 11.26981 which is equivalent to: ra(j2000) = 13h 14m 13.35s dec(j2000) = +11d 16' 11.3" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 107 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 (1.91 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 2.8 (+2.73/-2.37) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 250 seconds with the u filter starting 117 seconds after the bat trigger. there is a candidate afterglow in the list of sources generated on-board at ra(j2000) = 13:14:13.44 = 198.55602 dec(j2000) = +11:16:11.5 = 11.26985 with a 90%-confidence error radius of about 1.10 arc sec. this position is 1.4 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.47. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. 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 200306c: swift detection of a burst with an optical counterpart |
observations of the gamma-ray burst (grb) afterglows of gravitational wave (gw) detected binary neutron star (bns) mergers are likely to be valuable and, in the immediate future, rare. valuable, in part, because the afterglow encodes information about the inclination between the jet and earth, which can aid gw cosmology by breaking the distance-inclination degeneracy. rare because isotropy implies these bns mergers will predominantly occur at large inclination: earth will generally lie far off the jet axis and the afterglow emission will be delayed and dim. the observable afterglows will be prime targets for intensive and long-term follow-up. we present an updated theoretical modelling framework designed to make the best use of both photometric and astrometric observations of gw-grb afterglows, particularly at late times. as an application we perform a comprehensive analysis of the gw170817 afterglow, directly including high precision vlbi astrometry, faint source statistics, and modelling of the trans-relativistic evolution of the electron population. this analysis produces a measurement of the gw170817 viewing angle accurate to ~10% and allows a robust assessment of whether a new x-ray emitting source is contributing to the late-time observations. finally, we explore what we may be able to learn from observations in ligo o4 and beyond. | modelling the long-term electromagnetic counterparts to gravitational wave events |
at 14:54:48 ut, the swift burst alert telescope (bat) triggered and located grb 230328b (trigger=1162001). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 290.986, +80.016 which is ra(j2000) = 19h 23m 57s dec(j2000) = +80d 00' 58" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex grb structure with a duration of about 20 sec, followed by a bright flaring afterglow visible below 25 kev for at least 200 s. the peak count rate was ~4375 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 14:56:38.8 ut, 110.3 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 291.00418, 80.00951 which is equivalent to: ra(j2000) = 19h 24m 01.00s dec(j2000) = +80d 00' 34.2" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 25 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 (6.28 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.6 (+1.76/-1.56) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 114 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 19:24:01.84 = 291.00765 dec(j2000) = +80:00:34.5 = 80.00959 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 18.22 with a 1-sigma error of about 0.15. no correction has been made for the expected extinction corresponding to e(b-v) of 0.070. 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 230328b: swift detection of a burst with an optical afterglow |
at 05:47:26 ut, the swift burst alert telescope (bat) triggered and located grb 201020a (trigger=1000926). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 261.246, +31.425 which is ra(j2000) = 17h 24m 59s dec(j2000) = +31d 25' 30" 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 ~1800 counts/sec (15-350 kev), at ~17 sec after the trigger. the xrt began observing the field at 05:49:47.6 ut, 141.5 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 261.2279, 31.4288 which is equivalent to: ra(j2000) = 17h 24m 54.71s dec(j2000) = +31d 25' 43.8" with an uncertainty of 2.2 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. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 3.70 x 10^20 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 144 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 17:24:54.67 = 261.22779 dec(j2000) = +31:25:42.0 = 31.42834 with a 90%-confidence error radius of about 0.62 arc sec. this position is 5.4 arc sec. from the center of the xrt error circle. the estimated magnitude is 18.14 with a 1-sigma error of about 0.15. no correction has been made for the expected extinction corresponding to e(b-v) of 0.04. 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 201020a: swift detection of a burst with an optical counterpart. |
grb 200405b (gcn 27497) occurred in a field that has been observed 5 times as part of the askap variables and slow transients (vast; murphy et al. 2013) pilot survey between 2019-08-27 and 2020-01-25. we have searched for radio emission from the bat ground-calculated position and the 4 uncatalogued x-ray sources detected by swift (gcn 27500) and find no radio counterparts to a detection limit of ~1.5 mjy at 888 mhz. we also performed follow-up observations of all 5 positions with the atca between 2020-04-09 05:00-10:30 utc with 2x2 ghz bands centered on 5.5 and 9 ghz. no radio emission was detected coincident with any of the sources, we list 3-sigma upper limits below source 5.5 ghz (ujy) 9 ghz (ujy) bat pos 81 54 source 1 90 120 source 2 84 96 source 3 87 90 source 4 90 114 we do detect a radio source at coordinates of 04:10:26.8, -51:31:55 (offset 7.2 arcsec from source 4), coincident with wisea j041026.82-513155.2, with a flux density of ~4 mjy at 5.5 ghz and ~7 mjy at 9 ghz. this source is also detected in the vast pilot survey with a flux density of ~10 mjy. we do not consider this a candidate afterglow for the grb. further observations with atca and as part of the vast program are planned. thank you to csiro staff for supporting these observations during these especially difficult times. | grb 200405b: atca follow-up and askap limits on pre-burst radio emission |
at 19:58:03 ut, the swift burst alert telescope (bat) triggered and located grb 230405b (trigger=1163119). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 271.467, -47.070 which is ra(j2000) = 18h 05m 52s dec(j2000) = -47d 04' 12" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single-peaked structure with a duration of about 10 sec. the peak count rate was ~16000 counts/sec (15-350 kev), at ~2 sec after the trigger. the xrt began observing the field at 19:59:09.2 ut, 65.7 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 271.44108, -47.06898 which is equivalent to: ra(j2000) = 18h 05m 45.86s dec(j2000) = -47d 04' 08.3" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 63 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. no spectrum from the promptly downlinked event data is yet available to determine the column density. the initial flux in the 2.5 s image was 9.19e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 74 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. no correction has been made for the expected extinction corresponding to e(b-v) of 0.166. burst advocate for this burst is k. l. page (kimlpage1978 at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 230405b: swift detection of a burst |
report using the bepicolombo (mgns) data we have further improved the previous ipn box for grb 230307a (kozyrev et al., gcn circ. 33425). the coordinates of the updated 3 sigma error box are: --------------------------------------------- ra(2000), deg dec(2000), deg --------------------------------------------- center: 60.867 (04h 03m 28s) -75.382 (-75d 22' 57") corners: 60.846 (04h 03m 23s) -75.417 (-75d 25' 03") 61.006 (04h 04m 01s) -75.357 (-75d 21' 26") 60.889 (04h 03m 33s) -75.348 (-75d 20' 51") 60.728 (04h 02m 55s) -75.408 (-75d 24' 28") --------------------------------------------- the error box area is 8 sq. arcmin, and its maximum dimension is 5 arcmin (the minimum one is 1.8 arcmin). the sun distance was 80 deg. this box may be further improved. the distance between the ipn box center and x-ray/optical transient position (x-ray source #2 in burrows et al., gcn circ. 33429; levan et al., gcn circ. 33439; lipunov et al. gcn circ. 33441; o'connor et al., gcn circ. 33447; im et al., gcn circ. 33449; vanderspek et al., gcn circ. 33453) is 15 arcsec, which further strengthen the interpretation of transient as the burst afterglow. an updated triangulation map and healpix fits file are posted at http://www.ioffe.ru/lea/grbs/grb230307_t56646/ipn | further improved ipn localization for grb 230307a |
at 20:27:18 ut, the swift burst alert telescope (bat) triggered and located grb 201021c (trigger=1001130). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 12.550, -55.839 which is ra(j2000) = 00h 50m 12s dec(j2000) = -55d 50' 20" 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 25 sec. the peak count rate was ~1200 counts/sec (15-350 kev), at ~2 sec after the trigger. the xrt began observing the field at 20:29:00.6 ut, 102.0 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 12.53057, -55.86729 which is equivalent to: ra(j2000) = 00h 50m 07.34s dec(j2000) = -55d 52' 02.2" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 109 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 2.05 x 10^20 cm^-2 (willingale et al. 2013). 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 list of sources generated on-board at ra(j2000) = 00:50:06.85 = 12.52855 dec(j2000) = -55:51:56.7 = -55.86576 with a 90%-confidence error radius of about 1.10 arc sec. this position is 2.8 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.19. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. 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 201021c: swift detection of a burst with an optical counterpart |
at 10:49:55 ut, the swift burst alert telescope (bat) triggered and located grb 230815a (trigger=1185505). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 184.772, -58.065 which is ra(j2000) = 12h 19m 05s dec(j2000) = -58d 03' 53" 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 ~6000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 10:52:04.0 ut, 128.1 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 184.72347, -58.05386 which is equivalent to: ra(j2000) = 12h 18m 53.63s dec(j2000) = -58d 03' 13.9" with an uncertainty of 3.5 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 in excess of the galactic value (4.94 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 7.8 (+3.75/-3.24) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 2.07e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 155 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. data from the list of sources generated on-board are not available at this time. no correction has been made for the large, but uncertain, extinction expected. 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 230815a: swift detection of a burst |
at 02:50:03 ut, the swift burst alert telescope (bat) triggered and located grb 230728a (trigger=1181187). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 343.539, +28.151 which is ra(j2000) = 22h 54m 09s dec(j2000) = +28d 09' 03" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). due to a telemetry gap, bat lightcurve information is not immediately available. the xrt began observing the field at 02:51:33.5 ut, 90.3 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source with an enhanced position: ra, dec 343.51530, 28.17470 which is equivalent to: ra(j2000) = 22h 54m 03.67s dec(j2000) = +28d 10' 28.9" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 113 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (6.29 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 7.2 (+2.52/-2.21) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 7.13e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 99 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.079. burst advocate for this burst is c. salvaggio (chiara.salvaggio 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 230728a: swift detection of a burst |
we analyze the distribution of afterglow light-curve decay indices, α, for the data set of 176 gamma-ray bursts (grbs) with known redshifts, observed by swift from 2005 january to 2014 july. the fitted slopes and normalization parameters of the correlations presented in this paper are derived using the d'agostini (2005physics..11182d) method. the λcdm cosmology applied here uses the parameters h0=71km/s/mpc, ωλ=0.73, and ωm= 0.27. (1 data file). | vizier online data catalog: grb light-curve decay indices with swift (del vecchio+, 2016) |
at 11:23:51 ut, the swift burst alert telescope (bat) triggered and located grb 230805b (trigger=1183217). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 207.747, +31.185 which is ra(j2000) = 13h 50m 59s dec(j2000) = +31d 11' 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 60 sec. the peak count rate was ~1300 counts/sec (15-350 kev), at ~5 sec after the trigger. the xrt began observing the field at 11:27:03.3 ut, 192.3 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 207.74281, 31.19102 which is equivalent to: ra(j2000) = 13h 50m 58.28s dec(j2000) = +31d 11' 27.7" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 25 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 (1.41 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.6 (+2.86/-2.45) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 858 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 0.014. 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 230805b: swift detection of a burst |
swift-xrt obtained further observations of the field of the maxi-detected burst grb 210102b (guo et al. gcn circ. 29223). the data were collected between t0+209.5 ks and t0+312.5 ks for a total exposure time of 2.5 ks, and are entirely in photon counting (pc) mode. source 1 (burrows et al., gcn circ. 29230) is not detected down to a 3sigma upper limit of 0.004 ct/s. the source therefore has faded (with 2.2 sigma significance) with respect to the previous detection level (0.030 [+0.016, -0.012] ct s^-1 between t0+19.7 ks and t0+26.0 ks; burrows et al., gcn circ. 29230). we propose this source as the grb x-ray afterglow, in agreement with the results of the optical observations reported by pozanenko et al. (gcn circ. 29270). | grb 210102b: further swift-xrt observations |
at 09:46:31 ut, the swift burst alert telescope (bat) triggered and located grb 201017a (trigger=1000613). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 36.633, +66.673 which is ra(j2000) = 02h 26m 32s dec(j2000) = +66d 40' 22" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of at least 10 sec. data from ~t+10 s to ~t+100 s are currently unavailable. there might be additional burst emission during this interval. the peak count rate was ~1000 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 09:48:15.1 ut, 103.8 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 36.6186, 66.6787 which is equivalent to: ra(j2000) = 02h 26m 28.45s dec(j2000) = +66d 40' 43.4" with an uncertainty of 2.4 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 consistent with the galactic value of 5.70 x 10^21 cm^-2 (willingale et al. 2013). 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 1.20. 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 201017a: swift detection of a burst |
at 10:11:55 on 2021-09-10 ut, the swift burst alert telescope (bat) triggered and located a burst from the soft gamma repeater swift j1555.2-5402 (trigger=1072706). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 238.773, -54.055 which is ra(j2000) = 15h 55m 05s dec(j2000) = -54d 03' 16" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single high bin at the 64 ms timescale, consistent with the 4 ms trigger duration. the peak count rate on the 64 ms timescale was ~1300 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 10:13:14.4 ut, 78.8 seconds after the bat trigger. using promptly downlinked data we find an x-ray source with an enhanced position: ra, dec 238.78912, -54.06236 which is equivalent to: ra(j2000) = 15h 55m 09.39s dec(j2000) = -54d 03' 44.5" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 43 arcseconds from the bat onboard position, within the bat error circle, and consistent with the known position of swift j1555.2-5402. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data does not constrain the column density. uvot took a finding chart exposure of 150 seconds with the white filter starting 82 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the large, but uncertain, extinction expected. | swift detection of a burst from sgr swift j1555.2-5402 |
we have analysed 852s of swift/xrt data for grb 230423a (r.brivio et al., gcn circ. 33677), from t-t0=704.5 s to t+t0=4893.3 s after the bat trigger 1165354. the trigger was previously indicated as non-burst due to a low bat significance detection and the absence of an xrt counterpart (gcn circ. 33677). we found an uncatalogued fading source with coordinates: ra (j2000): 08h 10m 19.94s dec (j2000): -21d 55' 33.5" with an uncertainty of 3.8" (radius, 90% confidence). we propose this source as the x-ray afterglow of grb 230423a. the results of the xrt-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01165354 this circular is an official product of the swift-xrt team | grb 230423a: swift-xrt afterglow detection |
at 21:10:10 ut, the swift burst alert telescope (bat) triggered and located grb 210104b (trigger=1015919). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 53.601, +37.931 which is ra(j2000) = 03h 34m 24s dec(j2000) = +37d 55' 51" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a double-peaked structure with a duration of about 30 sec. the peak count rate was ~1000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 21:11:31.2 ut, 80.5 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 53.5539, 37.9302 which is equivalent to: ra(j2000) = 03h 34m 12.93s dec(j2000) = +37d 55' 48.7" with an uncertainty of 2.5 arcseconds (radius, 90% containment). this location is 133 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 (2.67 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 1.6 (+1.04/-0.80) x 10^22 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 83 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 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 0.79. 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 210104b: swift detection of a burst |
at 00:45:35 ut, the swift burst alert telescope (bat) triggered and located grb 180404a (trigger=821881). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 83.564, -37.170 which is ra(j2000) = 05h 34m 15s dec(j2000) = -37d 10' 10" 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 ~1900 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 00:47:02.1 ut, 86.5 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 83.54900, -37.16824 which is equivalent to: ra(j2000) = 05h 34m 11.76s dec(j2000) = -37d 10' 05.7" with an uncertainty of 4.2 arcseconds (radius, 90% containment). this location is 43 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. 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 89 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 05:34:11.63 = 83.54846 dec(j2000) = -37:10:03.9 = -37.16774 with a 90%-confidence error radius of about 0.65 arc sec. this position is 2.3 arc sec. from the center of the xrt error circle. the estimated magnitude is 19.40 with a 1-sigma error of about 0.16. no correction has been made for the expected extinction corresponding to e(b-v) of 0.04. burst advocate for this burst is j.d. gropp (jdg44 at psu.edu). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/too.html.) | grb 180404a: swift detection of a burst with an optical afterglow |
we join gravitational-wave and electromagnetic data to implement a combined simultaneous fit of the gw170817 event. the ligo-virgo analysis includes the estimation of the inclination, the angle of the binary with respect to the gravitationa-wave detector network line of sight. from the observations of the afterglow, instead, we can recover the viewing angle. the inclination and the viewing angle are supplementary angles, and can be treated as a single parameter. the value of the inclination that we recover from the fit is in agreement with the ligo-virgo previous works, with an uncertainty that is 10-fold smaller, thanks to contribution of the electromagnetic data. moreover, with the inclusion of the gravitational-wave data, the degeneracy between the viewing angle and the jet opening angle is broken. this procedure is useful not only for analyzing gw170817, but any gravitational-wave event with an electromagnetic counterpart. | the neutron star neutron star merger gw170817: a multi-messenger study |
we propose a continuation of our successful too program to observe short grbs detected by swift to identify the afterglow in x-rays by a sub-arcsecond position from chandra. our too program will increase the number of short grbs having an unambiguous host galaxy identification, and also provide a much less biased sample host galaxies of short grbs. we request a maximum of 2 toos for 20 ksec each based on the estimation of previous swift short grb observations. our trigger criteria are 1) swift short grbs localized by swift/xrt and 2) no afterglow confirmation in optical within 5 hours after the burst. we request <1-3 days response to our too, so that the afterglow can be observed while still bright. | identification of the host galaxy of swift short grbs by the chandra sub-arcsecond position |
the rapid infrared imager/spectrograph (rimas) is an instrument designed to observe gamma ray burst afterglows in the near infrared between 0.9 and 2.4 μm. dispersion in the moderate resolution mode (r~4000) is provided by a pair of znse grisms: one covering the y and j bands and the other covering the h and k. the quality of the hk grism was less than desired, suffering from moderate to severe chipping of the grooves and mediocre wavefront error. as a result, several improvements in technique were implemented during the machining of the yj grism. groove chipping results from cumulative tool wear, which was reduced when the crystal axes of the diamond tool were aligned with the cutting edges. minimizing the total length of cut also reduces tool wear. we created a raised elliptical mesa on the substrate corresponding to the optical footprint of the beam, so that grooves are machined only within the optical footprint. finally, we modified the machining fixture to prevent oil build up beneath the grism blank. removing the buoyancy effect of the oil eliminated astigmatism in the finished grating and reduced the rms wavefront error by nearly a factor of 3. | machining a yj band grism in znse for the rapid infrared imager spectrograph (rimas): improvements in technique |
our objective is to examine the early periods of grb optical afterglow light curves to determine what fraction of the sample shows significant afterglow emission when swift uvot first arrives on target. therefore, we require a sample of grb afterglows that (a) are optically bright enough that we can expect to detect the afterglow in settling observations at a significant fraction of the peak flux, (b) were observed soon after the trigger, and (c) have redshifts so that their observed properties can be transformed to the rest frame. with these criteria in mind, we have started with the sample of grbs studied by oates et al. (2012mnras.426l..86o). the sample of oates et al. (2012mnras.426l..86o) was drawn from the second uvot grb catalogue (roming et al. 2017apjs..228...13r), which contains all of the grbs observed with swift uvot from the launch of swift until 2010 december 25. for our study we have included only objects which have a peak v magnitude of =<16.0, which corresponds to a sample of 23 grbs. all of the grbs in the sample were observed with swift uvot in automated target (at) mode, and the analysis is restricted to those observations obtained in the initial observing segment, roughly the first 24h from the detection of the burst. for each grb the uvot v-band sky images and event data were retrieved from the uk swift science data centre (http://www.swift.ac.uk). table a1 gives the photometry for the stars in each grb field of view. (1 data file). | vizier online data catalog: swift observations of gamma-ray burst afterglows (page+, 2019) |
using the andicam instrument on the 1.3m telescope at ctio, we obtained optical/ir imaging of the error region of grb 170531b (gcn 21171, evans et al.) at two epochs (with mid-exposure times of 2017-06-01 04:22 ut & 08:19 ut). for each epoch, several dithered images were obtained with total summed exposure times amounting to 36 minutes in i and 30 minutes in j. no source is detected at the position of the x-ray/optical afterglow (gcn 21175, osborne et al.; gcn 21174, pozanenko et al.; gcn 21177, de ugarte postigo et al.; gcn 21178, schady & kruehler; gcn 21179, tyurina et al.) to the approximate 3-sigma limiting magnitudes listed below: mid-exposure time post-burst (hours) i-limit j-limit 6.33056 >20.8 >18.5 10.27333 >21.2 >18.7 (optical photometry is calibrated against usno-b1.0 stars and ir photometry is calibrated against 2mass stars in the field.) | grb 170531b: smarts optical/ir observations |
swift-xrt has performed further follow-up observations of the fermi/gbm (von kienlin gcn 30340) and swift/bat-guano detected burst grb 210626a (tohuvavohu et al., gcn circ. 30325), collecting 7.9 ks of photon counting (pc) mode data between t0+29.7 ks and t0+143 ks. the x-ray source detected in the first 1.4 ks of data as possible grb afterglow candidate (perri et al. gcn 30329) has faded more than 3 sigma in the latest observation, and it is thus confirmed as the x-ray afterglow of the burst. the results of the full analysis of the xrt observations are available at https://www.swift.ac.uk/xrt_curves/00021453/. this circular is an official product of the swift-xrt team. | grb 210626a: swift/xrt afterglow confirmation |
at 05:46:04 ut, the swift burst alert telescope (bat) triggered and located grb 220408a (trigger=1101675). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 202.402, +47.061 which is ra(j2000) = 13h 29m 36s dec(j2000) = +47d 03' 41" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a double-peaked structure with a duration of about 5 sec. the peak count rate was ~3500 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 05:47:53.1 ut, 109.0 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 202.41670, 47.06870 which is equivalent to: ra(j2000) = 13h 29m 40.01s dec(j2000) = +47d 04' 07.3" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 45 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.98 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 4.6 (+4.76/-3.79) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 112 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 13:29:39.72 = 202.41548 dec(j2000) = +47:04:09.5 = 47.06931 with a 90%-confidence error radius of about 0.91 arc sec. this position is 5.1 arc sec. from the center of the xrt error circle. the estimated magnitude is 20.76 with a 1-sigma error of about 0.22. no correction has been made for the expected extinction corresponding to e(b-v) of 0.042. we note that this grb is in a direction near to that of m51, the whirlpool galaxy, although well outside of its optical disk. determining whether this is a coincidence will require further study. burst advocate for this burst is r. caputo (regina.caputo at nasa.gov). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 220408a: swift detection of a burst with an optical counterpart, possibly associated with m51 |
"at 13:20:34.42 ut on 24 october 2023, the fermi gamma-ray burst monitor (gbm) triggered and located grb 231024a (trigger 719846439/231024556). this trigger was later followed up by goto (gompertz et al. 2023, gcn 34878), lcogt and ztf (iglesias-lópez et al. 2023, gcn 34881), and x-shooter (saccardi et al. 2023, gcn 34882) identifying a candidate afterglow (at2023vuc/goto23baj) and suggested it was the counterpart. the fermi gbm final localization was reported in gcn 34876. the angle from the fermi lat boresight is 89 degrees. the gbm light curve consists of a single peak with a duration (t90) of about 0.05s. the time-averaged spectrum from t0-0.064 to t0+0.064 s is best fit by a power law function with an exponential high-energy cutoff. the power law index is -0.76 +/- 0.26 and the cutoff energy, parameterized as epeak, is 516 +/- 202 kev. a band function fits the spectrum equally well with epeak = 519 +/- 203 kev, alpha = -0.75 +/- 0.26 and beta = -8.82 +/- 0.01. the event fluence (10-1000 kev) in this time interval is (2.9 +/- 0.4)e-07 erg/cm^2. the 64-msec peak photon flux measured starting from t0-0.06 s in the 10-1000 kev band is 8 +/- 1 ph/s/cm^2. due to the large gbm localization error radius of 12.6 degrees, as reported in gcn 34876, we are currently unable to confirm or deny the association between grb 231024a and at2023vuc/goto23baj. however, considered the spectroscopic classification of the optical transient as an early supernova we expect it to be unrelated to the gamma-ray trigger. the alignment in time and space is likely coincidental, in part due to the large localization region. the spectral analysis results presented above are preliminary; final results will be published in the gbm grb catalog: https://heasarc.gsfc.nasa.gov/w3browse/fermi/fermigbrst.html for fermi gbm data and info, please visit the official fermi gbm support page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" | grb 231024a: fermi gbm observation |
at 19:23:03 ut, the swift burst alert telescope (bat) triggered and located grb 220813a (trigger=1120270). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 81.501, -32.985 which is ra(j2000) = 05h 26m 00s dec(j2000) = -32d 59' 06" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single-peak structure with a duration of about 30 sec. the peak count rate was ~1200 counts/sec (15-350 kev), at ~2 sec after the trigger. the xrt began observing the field at 19:24:34.2 ut, 90.6 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 81.53235, -33.01546 which is equivalent to: ra(j2000) = 05h 26m 07.76s dec(j2000) = -33d 00' 55.7" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 144 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 (2.32 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.7 (+3.14/-2.65) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 100 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 05:26:07.57 = 81.53155 dec(j2000) = -33:00:58.9 = -33.01636 with a 90%-confidence error radius of about 0.67 arc sec. this position is 4.7 arc sec. from the center of the xrt error circle. the estimated magnitude is 19.61 with a 1-sigma error of about 0.17. no correction has been made for the expected extinction corresponding to e(b-v) of 0.022. 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 220813a: swift detection of a burst with an optical counterpart |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 220511a (delaunay et al. gcn circ. 32023), collecting 5.0 ks of photon counting (pc) mode data between t0+37.4 ks and t0+49.1 ks. the burst was also detected by fermi-gbm (gcn circ. 32018), agile (ursi et al., gcn 32021) and astrosat czti (gopalakrishnan et al., gcn 32028). 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): 287.4316 = 19:09:43.59 dec (j2000.0): +17.7297 = +17:43:46.9 error: 5.4 arcsec (radius, 90% conf.) count-rate: (4.7 +/- 1.2)e-3 ct s^-1 distance: 59 arcsec from swift/bat-guano position. flux: (1.94 +/- 0.51)e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 3: ra (j2000.0): 287.5100 = 19:10:2.41 dec (j2000.0): +17.7394 = +17:44:21.8 error: 4.0 arcsec (radius, 90% conf. [enhanced position]) count-rate: (3.9 [+1.2, -1.0])e-3 ct s^-1 distance: 219 arcsec from swift/bat-guano position. flux: (7.9 [+2.5, -2.1])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) a catalogued source was also detected. the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021498. this circular is an official product of the swift-xrt team. | grb 220511a: swift-xrt observations |
at 01:47:39 ut, the swift burst alert telescope (bat) triggered and located grb 231104a (trigger=1194500). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 23.789, +83.791 which is ra(j2000) = 01h 35m 09s dec(j2000) = +83d 47' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the available bat light curve (up to t+8s) showed a complex structure with a duration of at least 12 sec. the peak count rate was ~50,000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 01:49:10 ut, 90.2 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 23.8113, 83.7912 which is equivalent to: ra(j2000) = 01h 35m 14.7s dec(j2000) = +83d 47' 28" with an uncertainty of 3.8 arcseconds (radius, 90% containment). this location is 9 arcseconds from the bat onboard position. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. uvot took a finding chart exposure of 150 seconds with the white filter starting 860 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 25% of the bat 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 bat 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 0.157. 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 231104a: swift detection of a bright burst |
swift-xrt has performed follow-up observations of the fermi/gbm-detected burst grb 231129c in a series of observations tiled on the sky. the total exposure time is 1.5 ks, distributed over 4 tiles; the maximum exposure at a single sky location was 633 s. the data were collected between t0+19.3 ks and t0+35.4 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 2: ra (j2000.0): 11.1769 = 00:44:42.45 dec (j2000.0): -81.9936 = -81:59:37.0 error: 9.5 arcsec (radius, 90% conf.) count-rate: 0.0208 [+0.0113, -0.0084] ct s^-1 distance: 1341 arcsec from fermi/gbm position. flux: (8.6 [+4.7, -3.5])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) a catalogued source was also detected. the results of the xrt-team automatic analysis of the tiled xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/xrt_products/tiled_grb00117. this circular is an official product of the swift-xrt team. | grb 231129c: swift-xrt observations |
the afterglow of some short grbs displays a late-time rebrightening, visible in the near-infrared a few days after the burst. this late-time bump could be explained as kilonova emission, providing a direct link to neutron star mergers, and a compelling proof for the synthesis of heavy nuclei through the rapid neutron capture process (r-process). we propose a multi-wavelength follow-up campaign of a nearby (z<0.4) short grb in order to detect the expected kilonova bump and constrain its properties. multi-band observations, and in particular x-rays, are critical to pin down the nature of the observed rebrightening, and to distinguish it from the standard afterglow emission. | identifying the fingerprints of r-process heavy metals in a short grb |
at 04:56:57 ut, the swift burst alert telescope (bat) triggered and located grb 230409b (trigger=1163401). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 329.530, +52.854 which is ra(j2000) = 21h 58m 07s dec(j2000) = +52d 51' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the immediately available bat light curve starts at ~ a few seconds after the bat trigger time. the light curve shows a small hump from ~50 to 100 s, however, further ground data will be required to determine whether the hump is due to background fluctuation. the xrt began observing the field at 04:58:38.0 ut, 101.2 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 329.51486, 52.83228 which is equivalent to: ra(j2000) = 21h 58m 03.57s dec(j2000) = +52d 49' 56.2" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this location is 84 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 7.56 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 386 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. no correction has been made for the large, but uncertain, extinction expected. 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 230409b: swift detection of a burst |
photospheric emission from relativistic outflows may originate in two different regimes: photon decoupling within the outflow or radiative diffusion. i show that observed thermal component in the early afterglows of gamma-ray bursts can originate from such diffusive photospheres. | on diffusive photospheres in gamma-ray bursts |
at 21:00:34 ut, the swift burst alert telescope (bat) triggered and located grb 220427a (trigger=1104343). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 275.869, -56.253 which is ra(j2000) = 18h 23m 29s dec(j2000) = -56d 15' 09" 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 80 sec. the peak count rate was ~4000 counts/sec (15-350 kev), at ~10 sec after the trigger. the xrt began observing the field at 21:03:33.0 ut, 178.1 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 275.88860, -56.25508 which is equivalent to: ra(j2000) = 18h 23m 33.26s dec(j2000) = -56d 15' 18.3" 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. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.02 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 2.9 (+3.18/-2.73) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 181 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 18:23:33.32 = 275.88882 dec(j2000) = -56:15:18.3 = -56.25507 with a 90%-confidence error radius of about 0.61 arc sec. this position is 1.4 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.23 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.097. the original bat position notice found an approximate coincidence (~10 arcmin) with the position of igr j18244-5622 (which in turn is coincident with the sey2 galaxy ic 4709 at z=0.017). however, the position of the x-ray and optical counterpart excludes this source and galaxy, indicating that this is a new grb. 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 220427a: swift detection of a burst with an optical counterpart |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 190531b (axelsson et al. gcn circ. 24701), collecting 5.0 ks of photon counting (pc) mode data between t0+18.2 ks and t0+29.7 ks. eleven uncatalogued x-ray sources are detected, of which one ("source 8") is above the rass limit, and is therefore likely the grb afterglow. using 1291 s of pc mode data and 1 uvot image, we find an enhanced xrt position (using the xrt-uvot alignment and matching uvot field sources to the usno-b1 catalogue): ra, dec = 24.29620, -41.95841 which is equivalent to: ra (j2000): 01h 37m 11.09s dec(j2000): -41d 57' 30.3" with an uncertainty of 1.6 arcsec (radius, 90% confidence). this position is 3.4 arcmin from the fermi/lat position. the light curve can be modelled with a power-law decay with a decay index of alpha=1.0 (+/-0.3). a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 2.20 (+0.15, -0.14). the best-fitting absorption column is 9.1 (+1.2, -1.1) x 10^21 cm^-2, in excess of the galactic value of 1.8 x 10^20 cm^-2 (willingale et al. 2013). the counts to observed (unabsorbed) 0.3-10 kev flux conversion factor deduced from this spectrum is 4.2 x 10^-11 (9.0 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 9.1 (+1.2, -1.1) x 10^21 cm^-2 galactic foreground: 1.8 x 10^20 cm^-2 excess significance: 12.8 sigma photon index: 2.20 (+0.15, -0.14) if the light curve continues to decay with a power-law decay index of 1.0, the count rate at t+24 hours will be 0.14 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 kev flux of 5.9 x 10^-12 (1.3 x 10^-11) erg cm^-2 s^-1. the results of the xrt-team automatic analysis of the likely afterglow are at http://www.swift.ac.uk/too_grbs/00020895/source8.php. the results of the full analysis of the xrt observations are available at http://www.swift.ac.uk/too_grbs/00020895. this circular is an official product of the swift-xrt team. | grb 190531b: swift-xrt afterglow detection |
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