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at 22:24:42 ut, the swift burst alert telescope (bat) triggered and located grb 220715b (trigger=1116441). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 254.889, -33.597 which is ra(j2000) = 16h 59m 33s dec(j2000) = -33d 35' 48" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 50 sec. the peak count rate was ~2400 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 22:26:20.9 ut, 98.8 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 254.87520, -33.59766 which is equivalent to: ra(j2000) = 16h 59m 30.05s dec(j2000) = -33d 35' 51.6" with an uncertainty of 5.7 arcseconds (radius, 90% containment). this location is 41 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 3.58 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 102 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. because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. no correction has been made for the expected extinction corresponding to e(b-v) of 0.525. burst advocate for this burst is e. troja (nora.gsfc at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 220715b: swift detection of a burst |
"at 20:42:39.05 ut on 03 april 2022, the fermi gamma-ray burst monitor (gbm) triggered and located grb 220403b (trigger 670711364 / 220403863), which was also detected by the swift/bat and the swift/xrt (klingler et al. 2022, gcn 31820). additionally, the optical afterglow was detected by the swift/uvot (klingler et al. 2022, gcn 31820), d50 (jelinek et al. 2022, gcn 31821), nanshan/next (zhu et al. 2022, gcn 31823) and lbt (rossi 2022, gcn 31826). the angle from the fermi lat boresight at the gbm trigger time is 43 degrees. the gbm light curve shows broad rise with multiple peaks with a duration (t90) of about 28 s (50-300 kev). the time-averaged spectrum from t0-6.1 s to t0+21.5 s is best fit by a power law function with an exponential high-energy cutoff. the power law index is -1.2 +/- 0.1 and the cutoff energy, parameterized as epeak, is 79 +/- 3 kev. the spectrum is also well fit by a band function with epeak = 70 +/- 5, alpha = -1.1 +/- 0.1, and beta = -2.6 +/- 0.2. the event fluence (10-1000 kev) in this time interval is (5.2 +/- 0.1)e-06 erg/cm^2. the 1-sec peak photon flux measured starting from t0+7.6 s in the 10-1000 kev band is 4.3 +/- 0.2 ph/s/cm^2. the spectral analysis results presented above are preliminary; final results will be published in the gbm grb catalog: https://heasarc.gsfc.nasa.gov/w3browse/fermi/fermigbrst.html for fermi gbm data and info, please visit the official fermi gbm support page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" | grb 220403b: fermi gbm detection |
swift-xrt has performed follow-up observations of the swift/bat-guano-detected burst grb 220606b (tohuvavohu et al., gcn circ. 32167), collecting 4.9 ks of photon counting (pc) mode data between t0+44.9 ks and t0+68.8 ks. no credible x-ray afterglow candidate has been detected within the bat-guano error circle (tohuvavohu, gcn circ. 32170) down to a 0.3 - 10 kev count-rate upper limit of ~ 2e-3 ct/s (3sigma c.l.). 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/00021504. swift-uvot began settled observations 45.1 ks after the trigger. no optical afterglow consistent with the bat-guano position is detected. the 3.9 ks exposure in the white filter gives an upper limit of >21.9 mag. this circular is an official product of the swift team. | grb 220606b: swift follow-up observations |
continuing the recovery from the reaction wheel anomaly, swift has performed a follow-up observation of grb 220302a which occurred at 07:40:19 ut (troja et al., gcn 31661). the xrt began observing the field at 16:41:18.7 ut, 32459.3 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 301.43151, 49.38868 which is equivalent to: ra(j2000) = 20h 05m 43.56s dec(j2000) = +49d 23' 19.2" with an uncertainty of 4.7 arcseconds (radius, 90% containment). this location is 1.6 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. we cannot determine whether the source is fading at the present time. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 3.44 x 10^21 cm^-2 (willingale et al. 2013). uvot took a finding chart exposure of 150 seconds with the white filter starting 32463 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 0.216. burst advocate for this burst is e. troja (nora.gsfc at gmail.com). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 220302a: swift afterglow detection |
in this paper, we collect 54 gamma-ray burst (grb) afterglows rebrightening in x-ray, optical, and radio bands to build the biggest sample so far, of which 18 type-ic/b supernova (sn)-associated grbs have been deeply investigated. we confirm that the distribution of spectral luminosities of sn-associated grbs has a wider scope of five orders of magnitude. after excluding short- and low-luminosity sn/grbs, we obtain the mean light curves of high-luminosity sn/grbs at different radio frequencies. it is found that the mean radio light curves peak twice on the tens of days and several months in each since the burst trigger. there is a time delay between radio afterglows at different frequencies, i.e. the high-frequency emissions come earlier than those low-frequency ones. we study in detail the multiband rebrightening behaviors of grb 980425 and grb 030329 with the most radio observation data at present. unlike grb 980425, the rebrightening component contributed from grb 030329/sn 2003dh is indistinguishable. however, we predict that both sn/grbs will produce the considerable mjy-level rebrightening emissions from their individual sn remnants on the late-times of 103th years for grb 980425 and 64th years for grb 030329, which is observable for the current facilities and would be detected by the forthcoming radio telescopes. | rebrightening properties of multi-wave band afterglows in grbs associated with supernovae |
classical gamma-ray bursts have two distinct emission episodes: prompt emission from ultra-relativistic ejecta and afterglow from shocked circumstellar material. while both components are extremely luminous in known gamma-ray bursts, a variety of scenarios predict the existence of luminous afterglow emission with little or no associated high-energy prompt emission. we present ztf19abvizsw, the best candidate of this phenomenon to date. serendipitously discovered during follow-up of a recent gravitational-wave trigger and located in an active tess sector, it is hallmarked by a very fast-rising (< 30 minutes), luminous (mpeak ~ -24.4 mag) optical transient with accompanying luminous x-ray and radio emission. no gamma-ray emission consistent with the time and location of the transient was detected by fermi-gbm or by konus, placing strong limits on an accompanying gamma-ray burst. however, a moderately subluminous grb cannot be ruled out. an intensive search of four years of the ztf archive finds only a handful of comparable events, indicating that the rate of gamma-ray "dark" afterglows is at best comparable to the rate of classical grbs (at similar intrinsic optical luminosity). this suggests that gamma-ray-dark afterglows are not a dominant source of optical transients or that they are much fainter in the optical band than their grb analogs. | ztf19abvizsw: a gamma-ray burst afterglow without a gamma-ray burst |
swift-xrt has performed follow-up observations of the fermi/gbm-detected burst grb 230812b in a series of observations tiled on the sky. the total exposure time is 8.3 ks, distributed over 27 tiles; the maximum exposure at a single sky location was 4.6 ks. the data were collected between t0+25.4 ks and t0+38.1 ks, and are entirely in photon counting (pc) mode. four uncatalogued x-ray sources are detected, of which one ("source 7") is above the rass 3-sigma upper limit at this position, and is therefore likely the grb afterglow. using 4926 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 = 249.13196, +47.85892 which is equivalent to: ra (j2000): 16h 36m 31.67s dec(j2000): +47d 51' 32.1" with an uncertainty of 2.1 arcsec (radius, 90% confidence). this position is 106.5 arcmin from the fermi/gbm position, but only 6.7 arcmin from the fermi/lat position. the light curve can be modelled with a power-law decay with a decay index of alpha=1.8 (+/-0.4). a spectrum formed from the pc mode data can be fitted with an absorbed power-law with a photon spectral index of 1.82 (+/-0.15). the best-fitting absorption column is 9.6 (+4.3, -3.9) x 10^20 cm^-2, in excess of the galactic value of 2.0 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 3.4 x 10^-11 (4.0 x 10^-11) erg cm^-2 count^-1. a summary of the pc-mode spectrum is thus: total column: 9.6 (+4.3, -3.9) x 10^20 cm^-2 galactic foreground: 2.0 x 10^20 cm^-2 excess significance: 3.2 sigma photon index: 1.82 (+/-0.15) if the light curve continues to decay with a power-law decay index of 1.8, the count rate at t+24 hours will be 0.038 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 kev flux of 1.3 x 10^-12 (1.5 x 10^-12) erg cm^-2 s^-1. the results of the xrt-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021589. the results of the full analysis of the tiled xrt observations are available at https://www.swift.ac.uk/xrt_products/tiled_grb00115. this circular is an official product of the swift-xrt team. | grb 230812b: swift-xrt afterglow detection |
at 23:27:34 ut, the swift burst alert telescope (bat) triggered and located grb 230818a (trigger=1186032). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 285.883, +40.876 which is ra(j2000) = 19h 03m 32s dec(j2000) = +40d 52' 35" 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 10 sec. the peak count rate was ~6000 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 23:29:55.4 ut, 141.1 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 285.88966, 40.89504 which is equivalent to: ra(j2000) = 19h 03m 33.52s dec(j2000) = +40d 53' 42.1" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 70 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. 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 1.13 x 10^21 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. 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. 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 0.101. burst advocate for this burst is a. tohuvavohu (aaron.tohu 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 230818a: swift detection of a burst |
even after more than half a century from the discovery of gamma-ray bursts (grbs), the observed emission mechanism of these energetic astrophysical phenomena is still an enigma. the spectroscopic study of the prompt emission of grbs provides valuable information, yet, alone is inadequate to discriminate between the models. thus, one more constraining observable, polarisation, is of great importance for unravelling the emission mechanism. the polarisation measurement in x-ray astronomy is an emerging hot topic and quite challenging for transient events such as grbs. cadmium zinc telluride imager (czti) onboard astrosat is actively measuring polarisation in hard x-rays. in this paper, the novel technique of spectro-polarimetry has been presented for understanding the science of grbs. the joint observations from astrosat, fermi and swift have been utilised for understanding the observed emission mechanism in grbs. time-resolved spectro-polarimetric studies of a few bright grbs reveal variation in the polarisation with a concurrent change in spectrum. for the first time, a highly statistically significant measurement of linear polarisation and varying polarisation across a single pulse emission in grb~160821a have been reported. this study provides conclusive evidence for synchrotron emission produced in an ordered magnetic field. the spectro-polarimetric study grb~160325a presents a change in polarisation fraction with a simultaneous change in the spectrum. the composite modelling of the spectrum, polarisation and afterglow observations from grb~160325a has been utilised for understanding the nature of the outflow. more such polarisation measurements in hard x-rays along with spectral study constitute an important contribution to the science of grbs. | grb spectropolarimetry science with astrosat |
"at 06:08:30.73 ut on 27 august 2023, the fermi gamma-ray burst monitor (gbm) triggered and located grb 230827b (trigger 714809315/230827256). the optical afterglow of grb 230827b was also detected by ztf (gcn 34574), git (gcn 34576), and ako (gcn 34579). the location of the afterglow is consistent with the gbm on-ground calculated location, which is ra = 299.32, dec = +56.47 (j2000 degrees, equivalent to j2000 19h 57m 17s, +56d 28' 12"), with a statistical uncertainty of 2.17 degrees. the angle from the fermi lat boresight is 140 degrees. the gbm light curve shows a multi-peaked lightcurve with a duration (t90) of about 11 s (50-300 kev). the time-averaged spectrum from t0+0.002 to t0+10.240 s is best fit by a power law function with an exponential high-energy cutoff. the power law index is -1.37 +/- 0.05 and the cutoff energy, parameterized as epeak, is 352 +/- 52 kev. a band function fits the spectrum equally well with epeak= 256 +/- 51 kev, alpha = -1.28 +/- 0.08 and beta = -2.2 +/- 0.2. the event fluence (10-1000 kev) in this time interval is (1.08 +/- 0.04)e-05 erg/cm^2. the 1-sec peak photon flux measured starting from t0+4.7 s in the 10-1000 kev band is 16.4 +/- 0.9 ph/s/cm^2. the spectral analysis results presented above are preliminary; final results will be published in the gbm grb catalog: https://heasarc.gsfc.nasa.gov/w3browse/fermi/fermigbrst.html for fermi gbm data and info, please visit the official fermi gbm support page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" | grb 230827b / grb 230827256: fermi gbm observation |
the veritas imaging atmospheric cherenkov telescopes at the fred lawrence whipple observatory in southern arizona have been performing rapid follow-up observations of gamma-ray bursts in the very high-energy (>100 gev) band since 2006. grb 221009a occurred near the time of the full moon on a day when veritas observations were not scheduled. we report on observations obtained starting on ut 2022-10-11, about 36 hours after the burst — still under challenging bright moonlight conditions — and continuing until about 21 days after the burst. we also present results of a study of nearly one hundred additional grbs with few arcminute or better localizations having follow-up observations with veritas, and we discuss these observations in the context of the x-ray afterglow emission for these bursts. | veritas observations of grb 221009a and other gamma-ray bursts |
at 16:43:59 ut, the swift burst alert telescope (bat) triggered and located grb 231205b (trigger=1200812). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 54.154, +27.146 which is ra(j2000) = 03h 36m 37s dec(j2000) = +27d 08' 47" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single peak structure with a duration of about 40 sec. however there may be activity before the start of the immediately-available data, as the burst occurred during a pre-planned slew. the peak count rate was ~6000 counts/sec (15-350 kev), at t-3, before the nominal trigger time. the xrt began observing the field at 16:47:54.0 ut, 234.5 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 54.14912, 27.14099 which is equivalent to: ra(j2000) = 03h 36m 35.79s dec(j2000) = +27d 08' 27.6" with an uncertainty of 3.5 arcseconds (radius, 90% containment). this location is 23 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. no spectrum from the promptly downlinked event data is yet available to determine the column density. uvot took a finding chart exposure starting 237 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. burst advocate for this burst is p. a. evans (pae9 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 231205b: swift detection of a burst |
the detection of grb 170817 has offered a unique insight into the physics of binary neutron star mergers (bns), the production of short gamma-ray bursts (sgrb) jets, and their interaction with external media to produce an afterglow. using a publicly available model of afterglow light curves, named afterglow.py, we will implement monte-carlo simulations to generate the afterglow modeling parameters. these parameters will then be used to predict afterglow light curves of similar events at arbitrary observing angles. these predictions will guide our interpretation of future multi-messenger observations of these events. | modelling the afterglow and prompt emission of neutron star mergers |
relativistic jets are collimated outflows with speeds close to light speed, which are associated with gamma-ray bursts (grbs), active galactic nuclei (agns), and so on. this article mainly overviews recent developments of polarimetric studies of grbs and their afterglows in the gamma-ray and optical wavebands as well as the first detections of their radio polarization. polarimetric observations and theoretical modelings can address the emission mechanism, magnetic field structure, and energetics of grb jets and related collisionless plasma physics. some of the discussed key physics are common with agn jets. furthermore, we mention that polarimetry of agn jets and protoplanetary disks may be a novel approach to search for ultra-light axion dark matter. | polarimetric studies of grbs, agn jets, and axion dark matter |
the visible telescope (vt), which is the primary payload for the chinese-french space multi-band variable object monitor (svom) mission, is designed to observe the optical afterglow of gamma-ray bursts (grbs). while calibration is one of the key factors to validate that vt achieves its scientific objectives in terms of detection limit, photometric accuracy and photometric system deviation. in the dissertation, based on the scientific objectives and optomechanical parameters of svom vt, the calibration techniques for space-based astronomical telescopes are studied. we have carried out comprehensive characterization and high-precision calibration of vt qualification model in three phases: detector, instrumentation and in-orbit laboratory verification, and all tests have reached the desired results and meet the requirements of calibration indicators. | research on radiometric calibration of the svom visible telescope |
grb 070707 was the first short gamma-ray burst (grb) detected by integral and the optical afterglow was attributed to the prolonged activity of the central engine in the literature. here, we reanalyse the afterglow data and examine the physical origin of the emission. the redshift of this burst is uncertain and in this work we assume an association with a galaxy at the redshift of 0.2394 for a chance coincidence probability pcc = 0.046. it is found that the sole forward shock radiation cannot well reproduce the data, while including a kilonova component similar to at2017gfo is very helpful in reproducing the multiwavelength afterglow emission. the properties of the candidate host galaxy have been studied in detail; its high metallicity, low star formation rate, and old stellar population age are similar to the host galaxies of other grbs associated with kilonovae. in view of the facts that a kilonova signal was identified in the first short grb with detected optical emission (i.e. grb 050709) and the first short grb with gravitational wave detection (i.e. grb 170817a), and now the identification of a kilonova signature in the first integral short grb strongly indicates that kilonovae are rather common among the neutron star merger events. | the afterglow of grb 070707 and a possible kilonova component |
the not has a long tradition in the follow-up of gamma-ray bursts, starting with observations of the very first afterglow back in 1997. focus has been both on the physics of these events and their use as probes of the distant universe. twenty-five years later, the not has become a major worldwide contributor to this field. starting in 2017, the parallel branch of gravitational wave sources electromagnetic follow-up has also sprouted. this presentation reviews past seminal not contributions and highlights new science goals which can be tackled using the forthcoming nte, whose design has been optimized for transient sources. | relativistic explosions from the not |
grb 160509a was discovered by the fermi lat on 2016 may 09 at 08:59:04.36 utc (longo+ 2016gcn..19403...1l). we observed the afterglow with the vla starting at 0.36 days. we tracked the flux density of the afterglow over multiple epochs spanning 1.2-33.5ghz, using 3c48, 3c286, and 3c147 as flux and bandpass calibrators, and j2005+7752 as the gain calibrator. our vla observations spanning 0.36-20 days after the burst clearly reveal the presence of multiple spectral components in the radio afterglow. (1 data file). | vizier online data catalog: grb 160509a vla monitoring campaign results (laskar+, 2016) |
at 00:43:13 ut, the swift burst alert telescope (bat) triggered and located grb 180618a (trigger=842475). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 169.937, +73.848 which is ra(j2000) = 11h 19m 45s dec(j2000) = +73d 50' 52" 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 20 sec. the peak count rate was ~10000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 00:44:30.5 ut, 77.6 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 169.9415, 73.8358 which is equivalent to: ra(j2000) = +11h 19m 45.96s dec(j2000) = +73d 50' 08.9" with an uncertainty of 5.4 arcseconds (radius, 90% containment). this location is 44 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 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 86 seconds after the bat trigger. there is a candidate afterglow in the list of sources generated on-board at ra(j2000) = 11:19:45.78 = 169.94074 dec(j2000) = +73:50:13.3 = 73.83704 with a 90%-confidence error radius of about 1.10 arc sec. this position is 4.5 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.81. no correction has been made for the expected extinction corresponding to e(b-v) of 0.07. burst advocate for this burst is s. j. laporte (extragsam 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/too.html.) | grb 180618a: swift detection of a burst with an optical counterpart |
supernovae (sne), kilonovae (kne), tidal disruption events (tdes), optical afterglows of gamma ray bursts (grbs), and many other optical transients are important phenomena in time-domain astronomy. fitting the multi-band light curves (lcs) or the synthesized (pseudo-)bolometric lcs can be used to constrain the physical properties of optical transients. the (uv absorbed) blackbody module is one of the most important modules used to fit the multi-band lcs of optical transients having (uv absorbed) blackbody spectral energy distributions (seds). we find, however, that the seds of some sne show uv excesses, which cannot be fitted by the model including a (uv absorbed) blackbody module. we construct the bolometric lcs and employ the (cooling plus) \ni model to fit the constructed bolometric lcs, obtaining decent fits. our results demonstrate that the optical transients showing uv excesses cannot be fitted by the multi-band models that include (uv-absorbed) blackbody module, but can be well modeled by constructing and fitting their bolometric lcs. | the uv excesses of supernovae and the implications for studying supernovae and other optical transients |
boxfit calculates light curves and spectra for arbitrary observer times and frequencies and of performing (broadband) data fits using the downhill simplex method combined with simulated annealing. the flux value for a given observer time and frequency is a function of various variables that set the explosion physics (energy of the explosion, circumburst number density and jet collimation angle), the radiative process (magnetic field generation efficiency, electron shock-acceleration efficiency and synchrotron power slope for the electron energy distribution) and observer position (distance, redshift and angle). the code can be run both in parallel and on a single core. because a data fit takes many iterations, this is best done in parallel. single light curves and spectra can readily be done on a single core. | boxfit: gamma-ray burst afterglow light curve generator |
gamma ray bursts (grbs) represent one of the most fascinating topics in astrophysics. despite huge steps forward have been computed during the last two decades in our understanding of their origin, still a number of open questions need to be answered. among the most compelling ones there is the nature of the remnant compact object. whether a black hole or a neutron star is formed after the catastrophic main event has enormous implications not only on the physics of grbs but also on the equation of state of matter at extreme conditions, and provide interesting implications for gravitational wave observations from such sources with next generation detectors. the fast slew capabilities (minutes) of the x-ray telescope (xrt) onboard the neil gehrels swift observatory launched on november 2004 enabled to discovery several features not predicted by the standard fireball model in the grb early afterglow light curve stages (<0.5 day). in particular, a large fraction of grbs show a peculiar shallow flux decay phase ("plateau") on the origin of which no firm conclusion has been reached so far. plateaus might be the evidence of a prolonged energy injection from the grb central remnant. in this talk we discuss recent advances on the plateau properties in the framework of a spinning-down magnetar pumping energy into the fireball forward shock. | on the grb x-ray afterglow plateau origin |
fast radio bursts (frbs) are extra-galactic origin milli-second duration bright radio bursts. theoretically, frbs may produce optical counterparts with durations from milliseconds to hours. the frb optical counterparts may be detectable in future large field telescopes in china, including the china space station survey space telescope (csst), the 2.5-meter large field survey telescope (wfst) of the university of science and technology of china (ustc), and the purple mountain observatory (pmo), and earth 2.0 (et). the fast radio burst optical counterparts are grouped into millisecond time-scale optical counterparts, hourly time-scale optical counterparts, and optical afterglow for our study. the first two can be generated by the high-energy extension of frbs or the radio radiation of fast radio bursts and the inverse compton scattering of high-energy electrons. the event rates highly depend on the optical-radio flux ratio $\eta_{\rm \nu}$. for millisecond duration optical counterparts, the detection rate of wfst, csst, and et can reach hundreds per year in an ideal case. if $\eta_{\rm \nu} \sim 10^{-3}$, the corresponding annual detection rates of wfst and csst are in the order of 1, and the annual detection rate of et is 19.5. for the hourly optical counterparts, ideally, the age of the supernova remnant is 5 years, $\eta_{\nu}$ is about 10$^{-6}$, and the annual detection rates are above 100. the x-ray counterpart of frb 200428 indicates that frbs may produce relativistic outflow, which will interact with the interstellar medium to produce optical afterglows. combined with the standard afterglow model, the detectability of optical afterglow is explored with a simulation of fast radio bursts following the redshift and energy distribution from the literature. with a total energy-radio energy ratio similar to frb 200428, $\zeta=10^5$, the estimated annual detection rates of csst, wfst, and et are 1.3, 1.0, and 67, respectively. | detectability of fast radio burst optical counterparts with the future chinese wide field telescopes |
gamma-ray bursts (grbs) are fascinating events due to their panchromatic nature. we study optical plateaus in grb afterglows via an extended search into archival data. we comprehensively analyze all published grbs with known redshifts and optical plateaus observed by many ground-based telescopes (e.g., subaru telescope, ratir) around the world and several space-based observatories such as the neil gehrels swift observatory. we fit 500 optical light curves, showing the existence of the plateau in 179 cases. this sample is 75% larger than the previous one, and it is the largest compilation so far of optical plateaus. we discover the 3d fundamental plane relation at optical wavelengths using this sample. this correlation is between the rest-frame time at the end of the plateau emission, topt * , its optical luminosity, lopt, and the peak in the optical prompt emission, lpeak,opt, thus resembling the three-dimensional (3d) x-ray fundamental plane (the so-called 3d dainotti relation). we correct our sample for redshift evolution and selection effects, discovering that this correlation is indeed intrinsic to grb physics. we investigate the rest-frame end-time distributions in x-rays and optical (topt * , tx *), and conclude that the plateau is achromatic only when selection biases are not considered. we also investigate if the 3d optical correlation may be a new discriminant between optical grb classes and find that there is no significant separation between the classes compared to the gold sample plane after correcting for evolution. | the optical two and three-dimensional fundamental plane correlations for nearly 180 gamma-ray burst afterglows with swift/uvot, ratir, and the subaru telescope |
gamma-ray bursts (grbs) are the most luminous electromagnetic burst in the universe. they occur when a rapidly rotating massive star collapses or a binary neutron star merges. these events leave a newborn central compact object, either a black hole or neutron star, which launches relativistic jets that emit the luminous gamma-ray signals. these jets can accelerate non-thermal protons, which are expected to produce high-energy neutrinos via photohadronic interactions. this chapter briefly summarizes the current physical picture of grbs, and discusses neutrino emissions from grbs, including both prompt and afterglow phases. neutrinos from sub-classes of grbs, including low-luminosity grbs and short grbs, are also discussed. | neutrinos from gamma-ray bursts |
at 04:42:52 ut, the swift burst alert telescope (bat) triggered and located grb 191024a (trigger=931242). swift slewed to the burst after a delay to clear the earth limb observing constraint. the bat on-board calculated location is ra, dec 10.147, -67.139 which is ra(j2000) = 00h 40m 35s dec(j2000) = -67d 08' 21" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the first 8 seconds of the bat light curve showed a fred structure structure with an extrapolated duration of about 12 sec. (further light curve data will not be available until the full dataset is downlinked to the ground.) the peak count rate was ~2000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 04:56:41.7 ut, 829.1 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source located at ra, dec 10.11387, -67.14323 which is equivalent to: ra(j2000) = 00h 40m 27.33s dec(j2000) = -67d 08' 35.6" with an uncertainty of 4.5 arcseconds (radius, 90% containment). this location is 48 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 832 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 191024a: swift detection of a burst |
time resolved characterization of plasma x-ray emission represents an innovative technique to characterize non-equilibrium phases in electron cyclotron resonance ion sources (ecris). indeed, although ecris plasmas are usually in dynamical equilibrium, many relevant phenomena are characterized by fast transients and require a dedicated diagnostics to be fully investigated. in particular, time resolved diagnostics can be applied to characterize the x ray emission during the plasma turn on and off and during the turbulence phenomena induced by cyclotron-maser instability. this paper presents the experimental set-up used during the last campaign at measurement carried out at the istituto nazionale fisica nucleare -laboratori nazionali del sud (infn-lns), together with the main achieved results. particular relevance will be given to the characterization of the afterglow phase, which highlighted the existence of two electron populations characterized by different mean lifetime. evidences of x-ray bursts emission in the afterglow phase, compatible with cyclotron maser instability, will be also shown. | time resolved x-ray emission diagnostics in an axis-symmetric simple mirror trap |
neutron star mergers result in the formation of an accretion disk that evolves on timescales much longer than the orbital time, thereby ejecting mass that contributes to the r-process kilonova transient. it is widely accepted that angular momentum transport in astrophysical disks is mediated by magnetic turbulence, but thus far very few simulations of these disks have included this effect. i will present results of three-dimensional grmhd simulations of neutron star merger accretion disks around kerr black hole remnants, evolved for long enough to achieve completion of mass ejection far from the disk. comparing to viscous hydrodynamic simulations, we find that inclusion of magnetic fields result in a factor of two more mass ejected, at higher velocities, and with a wider electron fraction. given our initial magnetic field geometry, we also obtain a powerful relativistic jet capable of powering a short gamma-ray burst and its non-thermal afterglow. we acknowledge support from nserc of canada, university of alberta, northwestern university, simons foundation, david & lucile packard foundation, gordon & betty moore foundation, nasa, and doe office of science, office of nuclear physics. | long-term grmhd simulations of neutron star merger accretion disks |
at 22:26:10 ut, the swift burst alert telescope (bat) triggered and located grb 230628e (trigger=1177054). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 171.841, -11.447 which is ra(j2000) = 11h 27m 22s dec(j2000) = -11d 26' 47" 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 ~600 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 22:29:48.3 ut, 217.7 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 171.8499, -11.4641 which is equivalent to: ra(j2000) = +11h 27m 23.77s dec(j2000) = -11d 27' 50.2" with an uncertainty of 1.9 arcseconds (radius, 90% containment). this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. 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 221 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 0.040. 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 230628e: swift detection of a burst |
we propose a strategy for detecting and analyzing optical afterglows (oas) of long gamma-ray bursts (grbs) without the need to obtain their light curves. this approach is useful for the gaia satellite, which provides sampled optical ultra-low-dispersion spectroscopic observations of the sky. for this purpose, we show that most oas of long grbs display specific values of some of their color indices, representing synchrotron emission of the jet. they are stable in time during the event. these indices, which can be determined from the spectra, are very similar for the ensemble of oas with redshift z < 3.5 and display a strong clustering in some color-color diagrams. these indices also enable to constrain the properties of the local interstellar medium of grbs. the long-lasting mapping of the sky with the gaia instruments also gives us a hope to search for the so-called orphan afterglows, which, according to some authors, can be considerably more numerous than oas of the observed grbs. we also show how to resolve oas from other transients in the gaia data. the color indices and the properties of the quiescent sources (host galaxies of oas detectable later by the large ground-based telescopes at the co-ordinates of the oa determined by gaia) would tell us which one, among transients detected by gaia, is a grb oa. | perspectives of observing the color indices of optical afterglows of gamma-ray bursts with esa gaia |
gamma-ray bursts (grbs), which have isotropic energy up to $10^{54}$ erg, would be the ideal tool to study the properties of early universe: including dark energy, star formation rate, and the metal enrichment history of the universe. we will briefly review the progress on the field of grb cosmology. meanwhile, x-ray flares, which may have important clues to the central engine, are common phenomena in the grb afterglows. we present statistical results of x-ray flares, i.e., energy, duration time and waiting time distributions, and compare the results with solar flares. the similarity between the two kinds of flares are found, which may indicates that the physical mechanism of grb x-ray flares is magnetic reconnection. | grb cosmology and self-organized criticality in grbs |
one of the most energetic gamma-ray bursts grb 110731a, was observed from optical to gev energy range by fermi and swift observatories, and by the moa and grond optical telescopes. the multiwavelength observations over different epochs (from trigger time to more than 800 s) showed that the spectral energy distribution was better fitted by a wind afterglow model. we present a leptonic model based on an early afterglow that evolves in a stellar wind to describe the multiwavelength light curves observations. in particular, the origin of the lat emission is explained through the superposition of synchrotron radiation from the forward shock and synchrotron self-compton emission from the reverse shock. the bulk lorentz factor required in this model is $\gamma\simeq520$ and the result suggests that the ejecta must be magnetized. | the early afterglow and magnetized ejecta present in grb 110731a |
at 21:23:31 ut, the swift burst alert telescope (bat) triggered and located grb 191031d (trigger=932608). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 283.275, +47.639 which is ra(j2000) = 18h 53m 06s dec(j2000) = +47d 38' 19" 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 0.4 sec. the peak count rate was ~18000 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 21:24:59.8 ut, 88.8 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 283.2890, 47.6438 which is equivalent to: ra(j2000) = 18h 53m 09.37s dec(j2000) = +47d 38' 37.7" with an uncertainty of 2.3 arcseconds (radius, 90% containment). this location is 38 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. uvot took a finding chart exposure of 150 seconds with the white filter starting 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 0.08. this grb was also detected by fermi/gbm (trignum=191031891, gcn 26111), and the integral/spiacs event (trignum=8402). we note that the fermi automated circular has misnamed this event grb 191031c. burst advocate for this burst is v. d'elia (delia at ssdc.asi.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 191031d: swift detection of a short hard burst |
in this talk we propose that coherent radio emission of young energetic pulsars and some millisecond pulsars is produced in the magnetospheric current sheet. magnetic reconnection in the pulsar sheet proceeds in the plasmoid-dominated regime. collisions of plasmoids with each other and with the upstream magnetic field eject fast-magnetosonic waves, which escape from the plasma as electromagnetic waves in radio band. we illustrate this mechanism with first-principles kinetic plasma simulations, which allow us to compute the radiation spectrum. this model explains many features of observed short bursts of radio emission: their phase coincidence with the gamma-ray emission, nano-second duration, and extreme instantaneous brightness. | pulsar radio nanoshots as a low-frequency afterglow of relativistic magnetic reconnection |
this table records high-level information for each swift observation and provides access to the data archive. each record is associated with a single observation that contains data from all instruments on board swift. the bat is the large field of view instrument and operates in the 10-300 kev energy band. the narrow field instruments, xrt and uvot, operate in the x-ray and uv/optical regime, respectively. an observation is defined as a collection of snapshots, where a snapshot is defined as the time spent observing the same position continuously. because of observing constraints, the length of a snapshot can be shorter than a single orbit and it can be interrupted because the satellite will point in a different direction of the sky or because the time allocated to that observation ends. the typical swift observing strategy for a gamma ray burst (grb) and/or afterglow, consists of a serious of observations aimed at following the grb and its afterglow evolution. this strategy is achieved with two different type of observations named automatic targets and pre-planned targets. the automatic target is initiated on board soon after an event is triggered by the bat. the figure of merit (fom) algorithm, part of the observatory's autonomy, decides if it is worth requesting a slew maneuver to point the narrow field instruments (nfi) on swift, xrt and uvot, in the direction of the trigger. if the conditions to slew to the new position are satisfied, the automatic target observation takes place; all the instruments have a pre-set standard configuration of operating modes and filters and about 20000 seconds on source will be collected. the pre-planned target observations instead are initiated from the ground once the trigger is known. these observations are planned on ground and uploaded onto the spacecraft. (1 data file). | vizier online data catalog: swift master catalog (heasarc, 2004-) |
gamma ray bursts (grbs) are extreme explosions that occur randomly in the universe. they release more energy in seconds than what the sun emits in its entire lifetime. we present a study focusing on grb afterglow flares; what are they? why do they occur? how are they related to the prompt grb itself? in order to begin the process of figuring this out, we fit ~350 x-ray afterglow light curves collected by the swift x-ray telescope. the fitting procedure uses the superposition of two mathematical models; the norris function and broken power laws. we minimized the fit residuals to establish a good fit, and search for a pattern in the residuals (hakkila et al.2015) which may show a characteristic signature present in prompt grb light curves. this residual signature may be related to details of the shock physics and provide a much better understanding of relativistic shocks. | gamma-ray bursts light curve fitting with swift xrt |
the rapid infrared imager/spectrograph (rimas) is an instrument designed to observe gamma ray burst afterglows. dispersion in the moderate resolution mode (r 4000) is provided by znse grisms: one covering the y and j bands and the other covering the h and k. each has a clear aperture of 44 mm. for the hk grism the blaze is 49.9° with a 20 line/mm period. the grooves cover an area of 69 mm x 45 mm. the hk grism was diamond machined on the precision engineering research lathe (perl) at llnl. chipping of the grooves increased from moderate to severe as the cutting progressed resulting in excess scattered light and reduced diffraction efficiency. high magnification optical microscopy and sem of the cutting edges indicated damage to the tool caused by wear. a comparison of the outcomes of znse gratings and grisms machined at llnl indicated that chipping was minimal in low blaze angle cuts but moderate to severe with the blaze angle near 45° as in the hk grism. vendor records showed that the (100) crystal planes of the diamond were aligned parallel to the tool shank. therefore the (100) planes are closely aligned with the cutting edge in low blaze angle tools but 45° off in the hk tool. we believe that this misalignment of the cutting edge with the (100) crystal plane in the hk tool produced excessive tool wear resulting in the chipped grooves observed. | machining of znse grisms for the rapid infrared imager spectrograph (rimas): effect of diamond crystal orientation |
long gamma-ray burst grb 151027a was observed by all three detectors onboard the swift spacecraft, and many more, including maxi, konus-wind and fermi gbm/lat instruments. this revealed a complex structure of the prompt and afterglow emission, consisting of a double-peak gammaray prompt with a quiescent period and a hrf/sxf within the x-ray afterglow, together with multiple bb components seen within the time-resolved spectral analysis. these features, within the fireshell model, are interpreted as the manifestation of the same physical process viewed at different angles with respect to the hn ejecta. here we present the time-resolved and time-integrated spectral analysis used to determine the energy of the e - e + plasma e tot and the baryon load b. these quantities describe the dynamics of the fireshell up to the transparency point. we proceed with the light-curve simulation from which cbm density values and its inhomogeneities are deduced. we also investigate the properties of grb 140206a, whose prompt emission exhibits a similar structure. | structure of the prompt emission of grb 151027a within the fireshell model |
a class of long gamma-ray bursts (grbs) presenting light curves with an extended plateau phase in their x-ray afterglows obey a two parameter correlation (dainotti et al. 2008) betweenthe rest frame end time of the plateau, t_a, and its corresponding x-ray luminosity, l_{a}. this correlation is a useful tool towards cosmological parameter inferences and yields important constraints on physical grb models.we here show through an analysis of 122 swift long grbs with known redshifts and presentingafterglow plateaus, that including also the peak luminosity in the prompt emission, l_{peak}, as a third parameter, a fundamental plane appears. a careful statistical analysis excludes the possibility of this correlation being due to detection thresholds or observational selection biases. the correlation is tightest when a class-specific grb sample is defined excluding grb-sne, x-ray flashes and short grbs with extended emission, and required also to have a good data coverage and an almost flat plateau. the intrinsic scatter, σ_{int}=0.27 ± 0.04, for the three-parameter correlation for this specific subclass (40 grbs) is 53.5% smaller than the (l_{a}, t_a) one,making this the tighest three parameter correlation involving the plateau phase. this result will hence enhance cosmological parameter determinations and grb model constraints. finally, we also show that a slightly noisier correlation is also present between l_{peak} and a proxy of the total energy emitted during the plateau phase, the product l_{a}t_{a}, hinting at the presence of an energy scaling between prompt and afterglow phases. | a fundamental plane for gamma ray bursts with x-ray plateaus |
searches for electromagnetic counterparts of gravitational-wave signals have redoubled since the first detection in 2017 of a binary neutron star merger with a gamma-ray burst, optical/infrared kilonova, and panchromatic afterglow. yet, one ligo/virgo observing run later, there has not yet been a second, secure identification of an electromagnetic counterpart. this is not surprising given that the localization uncertainties of events in ligo and virgo's third observing run, o3, were much larger than predicted. we explain this by showing that improvements in data analysis that now allow ligo/virgo to detect weaker and hence more poorly-localized events have increased the overall number of detections, of which well-localized, "gold-plated" events make a smaller proportion overall. we present simulations of the next two ligo/virgo/kagra observing runs, o4 and o5, that are grounded in the statistics of o3 public alerts. to illustrate the significant impact that the updated predictions can have, we study the follow-up strategy for the zwicky transient facility. realistic and timely forecasting of gravitational-wave localization accuracy is paramount given the large commitments of telescope time and the need to prioritize which events are followed up. we include a data release of our simulated localizations as a public proposal planning resource for astronomers. this is an archive of the github repository https://github.com/lpsinger/observing-scenarios-simulations, containing all of the scripts to reproduce the simulated gravitational-wave detections and localizations on a high performance computing cluster scheduled with htcondor or pbs. | data-driven expectations for electromagnetic counterpart searches based on ligo/virgo public alerts: cluster scripts |
gamma ray bursts (grbs) are the the most luminous electromagnetic events known to occur throughout the universe. these violent explosions produce relativistic jets in a short burst of prompt emission and are followed by an afterglow emitted across the electromagnetic spectrum. during the afterglow, there are periods of sporadic increase in the x-ray flux, known as flares. only ~1/2 of all grbs produce flares. we present a sample selection of the brightest isolated flares observed by the swift x-ray telescope (xrt). using light curves from the xrt team repository at the university of leicester between 2005 and 2014, and our own light curve fits, the sample was filtered using a stringent set of criteria. we selected bursts that: 1) had a high peak flare flux to afterglow ratio, and/or 2) a high fluence (integrated flux). by further analyzing these flares, we will study the structure of flares, searching for the three components that have been seen in isolated prompt emission pulses: an initial small rapidly decaying pulse, followed by the main flare which then decays over time and is followed by another small but slower decaying pulse. seeing a similar behavior in x-ray flares as we see in prompt pulses will inform models for the physics of relativistic shocks. | a search for structure in gamma ray burst x-ray flares confirming whether they are similar to the three pulse structure found in propt emission pulses |
at 01:40:46 ut, the swift burst alert telescope (bat) triggered and located grb 170331a (trigger=744791). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 323.782, -24.414, which is ra(j2000) = 21h 35m 08s dec(j2000) = -24d 24' 48" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve shows a complicated set of overlapping peaks with a total duration of about 25 sec. the peak count rate was ~1400 counts/sec (15-350 kev), at ~5 sec after the trigger. the xrt began observing the field at 01:42:50.6 ut, 124.2 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 323.79260, -24.38604 which is equivalent to: ra(j2000) = 21h 35m 10.22s dec(j2000) = -24d 23' 09.7" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 105 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (4.65 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.1 (+3.11/-2.65) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 127 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 0.05. burst advocate for this burst is a. melandri (andrea.melandri at brera.inaf.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/too.html.) | grb 170331a: swift detection of a burst |
thanks to many space-borne detectors such as the swift and fermi satellites and numerous ground-based followed-up telescopes, gamma-ray bursts (grbs) are now quickly covered in virtually every wavelength in the electromagnetic spectrum. covering the energy range above 30 mev, the fermi-lat has seen more than a hundred grbs and have seen tens of photons above 10 gev from several bright grbs, limited by its collective area. in this talk, i will review recent grb observations at >10 gev up to nearly a day after the burst, including that of grb 130427a and some recent grbs, and discuss the corresponding radiation mechanisms in the afterglow at these energies. | gamma-ray bursts in the one of the last frontiers: the 10-100 gev energy band |
the recent discovery of gw170817 the first gravitational-wave detection where we also observed electromagnetic signals has enabled new studies of merging compact objects. what have we since learned about the radiation that emerges from these collisions?signs of a mergerbefore gw170817 was observed, our models predicted that when two compact objects either two neutron stars, or a neutron star and a black hole merge, a number of observable signals result:a spike of gravitational waves as the objects conclude their death spiral,a short gamma-ray burst, an explosion of gamma rays thought to be produced in the relativistic jets launched during the merger,an afterglow spanning x-rays to radio, caused when the jets slam into the surrounding environment and decelerate, andan optical/near-infrared transient signal called a kilonova, which occurs when neutron-rich ejected material forms heavy elements that then undergo radioactive decay.last augusts binary-neutron-star merger confirmed this picture beautifully: the discovery of gravitational-wave signal gw170817 was followed by detections of short gamma-ray burst sgrb 170817a and later observations of kilonova at 2017gfo.but though this was the first time for all of these signals to come together for a source, it wasnt our first observation of a short gamma-ray burst or a kilonova! how do past detections compare to this new one, and what can we consequently learn about the bursts of radiation from merging compact objects? a team of scientists led by ben gompertz (university of warwick, uk) have now tackled these questions.model fit to the kilonova at 2017gfo. [gompertz et al. 2018]diversity of kilonovaegompertz and collaborators compared the optical and near-infrared light curves of kilonova at 2017gfo to equivalent light curves for a sample of a dozen nearby short gamma-ray bursts. what they found was a diversity of signals: some with no evidence of a kilonova, despite observations sensitive enough to pick up a signal several magnitudes fainter than at 2017gfo; some with confirmed or suspected kilonovae brighter than at 2017gfo; and some with afterglows so bright that they could be masking kilonovae that are brighter still.how can we explain these vastly different kilonova outcomes from different mergers? the authors demonstrate that neither line-of-sight dust interference nor viewing angles can explain the differences we see in the optical and near-infrared signals.its all in the starting players?magnitudes of the optical and near-infrared emission for a sample of 12 short gamma-ray bursts, as compared to the kilonova at 2017gfo. [gompertz et al. 2018]instead, gompertz and collaborators propose that a dichotomy might exist in the short-gamma-ray-burst population, between those created by the merger of two neutron stars, and those created by the merger of a neutron star with a black hole. a neutron-starblack-hole merger can produce as much as ten times more ejecta than a binary-neutron-star merger perhaps allowing the former to power observable kilonovae, while the latter produce much fainter signals.future observations of these events can confirm or deny this picture, depending on whether the magnitude of kilonova emission continues to display a gap in brightness between two populations, or if it instead forms a continuum. either way, we can look forward to learning more about these explosive collisions soon!citationb. p. gompertz et al 2018 apj 860 62. doi:10.3847/1538-4357/aac206 | piecing together the light from colliding stars |
at 17:49:01 ut, the swift burst alert telescope (bat) triggered and located grb 190611a (trigger=907950). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 324.769, -56.082 which is ra(j2000) = 21h 39m 05s dec(j2000) = -56d 04' 54" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a complex structure with a duration of about 10 sec. the peak count rate was ~900 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 17:50:55.4 ut, 113.5 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 324.72043, -56.07370 which is equivalent to: ra(j2000) = 21h 38m 52.90s dec(j2000) = -56d 04' 25.3" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 102 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (3.25 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 4.3 (+3.64/-3.06) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 150 seconds with the white filter starting 116 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers none of the xrt error circle. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the expected extinction corresponding to e(b-v) of 0.04. burst advocate for this burst is v. d'elia (delia at ssdc.asi.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 190611a: swift detection of a burst |
swift-xrt has performed follow-up observations of the integral-detected burst grb 200914a (mereghetti et al. gcn circ. 28419), collecting 3.2 ks of photon counting (pc) mode data between t0+8.9 ks and t0+49.2 ks. one uncatalogued x-ray source has been detected consistent with being within 148 arcsec of the integral position, it is below the rass limit and shows no definitive signs of fading. therefore, at the present time we cannot confirm this as the afterglow. details of this source are given below: source 1: ra (j2000.0): 254.5202 = 16:58:4.84 dec (j2000.0): -36.2782 = -36:16:41.6 error: 6.5 arcsec (radius, 90% conf.) count-rate: (2.42 [+1.23, -0.93])e-3 ct s^-1 distance: 53 arcsec from integral position. flux: (10.0 [+5.0, -3.8])e-14 erg cm^-2 s^-1 (observed, 0.3-10 kev) within the 90% error circle of source 1 we note the presence of a relatively bright ir source reported in the 2mass and allwise catalogues (2mass 16580467-3616436 / allwise j165804.63-361643.5). 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/00021033. this circular is an official product of the swift-xrt team. | grb 200914a: swift-xrt observations |
swift-xrt has performed follow-up observations of the fermi-gbm and swift/bat (guano)-detected burst grb 200714e (gcn circs. 28098 and 28103), collecting 2.2 ks of photon counting (pc) mode data between t0+37.3 ks and t0+44.5 ks. 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): 196.8225 = 13:07:17.41 dec (j2000.0): -51.6390 = -51:38:20.4 error: 3.1 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.0138 +/- 0.0033 ct s^-1 distance: 96 arcsec from swift/bat position. flux: (6.2 +/- 1.5)e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) the results of the xrt-team automatic analysis of the xrt observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/too_grbs/00021017. further observations are planned. this circular is an official product of the swift-xrt team. | grb 200714e: swift-xrt observations |
at 09:58:51 ut, the swift burst alert telescope (bat) triggered and located grb 201001a (trigger=998344). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 110.070, -2.210 which is ra(j2000) = 07h 20m 17s dec(j2000) = -02d 12' 36" 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 30 sec. the peak count rate was ~1000 counts/sec (15-350 kev), at ~4 sec after the trigger. the xrt began observing the field at 10:00:47.5 ut, 116.0 seconds after the bat trigger. using promptly downlinked data we find an uncatalogued x-ray source with an enhanced position: ra, dec 110.0806, -2.2103 which is equivalent to: ra(j2000) = 07h 20m 19.33s dec(j2000) = -02d 12' 37.2" with an uncertainty of 4.4 arcseconds (radius, 90% containment). this location is 38 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. no spectrum from the promptly downlinked event data is yet available to determine the column density. uvot took a finding chart exposure of 150 seconds with the white filter starting 119 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 0.12. 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 201001a: swift detection of a burst |
at 21:33:41 ut, the swift burst alert telescope (bat) triggered and located grb 191004b (trigger=927839). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 49.177, -39.613, which is ra(j2000) = 03h 16m 42s dec(j2000) = -39d 36' 46" 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 40 sec. the peak count rate was ~9500 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 21:34:39.3 ut, 57.7 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 49.20403, -39.63494 which is equivalent to: ra(j2000) = 03h 16m 48.97s dec(j2000) = -39d 38' 05.8" with an uncertainty of 3.9 arcseconds (radius, 90% containment). this location is 108 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. no spectrum from the promptly downlinked event data is yet available to determine the column density. the initial flux in the 2.5 s image was 1.81e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 68 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 03:16:49.10 = 49.20458 dec(j2000) = -39:38:03.3 = -39.63425 with a 90%-confidence error radius of about 0.62 arc sec. this position is 2.9 arc sec. from the center of the xrt error circle. the estimated magnitude is 18.00 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. 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 191004b: swift detection of a burst with an optical counterpart |
since its commissioning at eso's very large telescope in 2009, the x-shooter spectrograph has become the reference instrument in gamma-ray burst (grb) afterglow spectroscopy. during this time our collaboration has collected more than 70 spectra of grb afterglows, with redshifts ranging from 0.06 to 6.3. thanks to their extreme luminosity and simple intrinsic shape, grb spectra are optimal tools for the study of galactic environments at basically any redshift. being produced by the death of short-lived massive stars, they are also tracers of star formation.i will present the sample of absorption spectral features identified in x-shooter's grb spectra describing observation and analysis techniques. the different features are compared with the characteristics of the explosion (duration, spectral shape, energetics, etc.) and with the properties of the host galaxy (mass, age, etc.) to improve our understanding of the nature of the explosions and how they interact with their environments. using the large redshift range of the spectra collection we perform studies of the evolution of grb environments across the history of the universe and their relation with the evolution of star formation. | the x-shooter sample of grb afterglow spectra: properties of the absorption features |
at 14:58:34 ut, the swift burst alert telescope (bat) triggered and located grb 190719c (trigger=915381). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 240.210, +12.977 which is ra(j2000) = 16h 00m 50s dec(j2000) = +12d 58' 39" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a total duration of about 100 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 14:59:35.3 ut, 60.9 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source located at ra, dec 240.20700, 12.99995 which is equivalent to: ra(j2000) = 16h 00m 49.68s dec(j2000) = +12d 59' 59.8" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 83 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (4.69 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 3.9 (+3.40/-2.88) x 10^21 cm^-2 (90% confidence). the initial flux in the 0.1 s image was 1.69e-08 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 71 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. the fermi gbm team announced the detection of grb 190719c (gcn circ 25104). given the temporal coincidence, it is likely that this is the same burst. 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 190719c: swift detection of a burst |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 200524a (fana dirirsa et al. gcn circ. 27797), collecting 5.0 ks of photon counting (pc) mode data between t0+36.4 ks and t0+55.7 ks. four uncatalogued x-ray sources are detected, of which one ("source 6") is believed to be the afterglow. using 1644 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 = 213.04474, +60.90538 which is equivalent to: ra (j2000): 14h 12m 10.74s dec(j2000): +60d 54' 19.4" with an uncertainty of 4.4 arcsec (radius, 90% confidence). this position is 9.2 arcmin from the fermi/lat position, and 3 arcsec from ztf20abbiixp (ho et al., gcn 27799). the light curve can be modelled with a power-law decay with a decay index of alpha=3.42 (+0.06, -2.83). the results of the xrt-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021001. the results of the full analysis of the xrt observations are available at https://www.swift.ac.uk/too_grbs/00021001. this circular is an official product of the swift-xrt team. | grb 200524a: swift-xrt afterglow detection |
at 07:36:49 ut, the swift burst alert telescope (bat) triggered and located grb 200219a (trigger=957271). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 342.644, -59.108 which is ra(j2000) = 22h 50m 35s dec(j2000) = -59d 06' 29" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a single peak with a duration of about 1 sec. the peak count rate was ~15000 counts/sec (15-350 kev), at ~0.3 sec after the trigger. the xrt began observing the field at 07:37:56.6 ut, 67.5 seconds after the bat trigger. using promptly downlinked data we find a bright, fading, uncatalogued x-ray source with an enhanced position: ra, dec 342.6376, -59.1200 which is equivalent to: ra(j2000) = 22h 50m 33.02s dec(j2000) = -59d 07' 11.8" with an uncertainty of 2.5 arcseconds (radius, 90% containment). this location is 44 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 (1.93 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 6.1 (+3.05/-2.63) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 4.22e-09 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. 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 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 200219a: swift detection of a short burst |
gamma-ray bursts (grbs) by virtue of their high luminosities are observed up to redshift z=9.4 (cucchiara et al. 2011), far beyond the most distant quasars orgalaxies. and thus have the potential to be vital cosmological probes of earlier processes in theuniverse, such as reionization, evolution of the star formation rate (sfr), in general, and formation of the firstgeneration (population iii) stars. this requires a relatively large sample of grbs with knownredshifts and well defined observational selection effects. most grb instruments provide sampleswith a well defined prompt gamma-ray peak flux threshold. however, samples with redshift, requiringlocalization at x-rays and optical-uv follow up observations, suffer from more complex truncations,which hampers the progress to this end. the swift satellite, the most successful instruments formeasuring spectroscopic redshifts of grbs, has provided redshifts only about one-third of grbs itdetected. the situation is even less promising for other instruments. thus, for more than 20 yearsthere have been attempts to increase the number of grbs with known z via a theoretical estimate ofredshift (so called pseudo-redshifts) using grb relations, but these approaches have led toinaccurate predictions. thus, we adopt here supervised machine learning approaches to estimateredshifts for grbs using existing data from many instruments; swift-(bat,xrt), fermi-gbm andkonus-wind. these methods will also allow us to estimate possible non-linear relations between the redshift andother grb characteristics. our approach brings a novelty on this research area,because, for the first time, it adds the afterglow plateau emission characteristics. weobtained best results using the ``generalized additive" model with a correlation coefficient of0.91 between the predicted and the observed redshifts and an overall dispersion of $0.2$.the addition of afterglow parameters improves the predictions by 45% compared to previous resultsin the published literature. we also show that using the predicted redshifts we obtaindistributions and cosmological evolutions very similar to those obtained from actual measuredredshifts. | use of supervised machine learning for determination of redshifts of gamma-ray bursts |
we observed again the optical afterglow of the bright, low-redshift grb 180728a (starling et al., gcn 23046; lipunov et al., gcb 23048; rossi et al., gcb 23055) with the eso vlt ut2 equipped with the x-shooter spectrograph. | grb 180728a: no evidence of sn in early vlt/x-shooter spectra |
gamma-ray burst (grb) afterglow modeling has long relied on only synchrotron emission to calculate the broadband spectrum and light-curves. although this works for many afterglows, certain physical conditions would require that synchrotron self-compton (ssc) effects be considered to properly describe the afterglow emission. even in cases where ssc effects are small, their inclusion further constrains grb parameter space. we present modifications to the hydrodynamic afterglow fitting routine boxfit that allows for the rigorous treatment of ssc effects for both electron cooling and emission on the afterglow spectrum over all of parameter space, by producing a smoothened approximation of the inverse-compton y parameter that is continuous and applicable for all times and physical parameter values. we further address first order klein-nishina corrections to ssc effects and modify our y parameter accordingly. finally, we discuss the overall effects of ssc on the parameter space when compared with synchrotron-only model fits of the emission, first by discussing the outcomes of synthetic data fitting, then by comparing results from fitting the afterglow of grb 070125. | beyond synchrotron effects in gamma-ray burst afterglows |
at 17:10:03 ut, the swift burst alert telescope (bat) triggered and located grb 190821a (trigger=921722). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 250.077, -34.022 which is ra(j2000) = 16h 40m 18s dec(j2000) = -34d 01' 16" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 100 sec. the peak count rate was ~2200 counts/sec (15-350 kev), at ~30 sec after the trigger. the xrt began observing the field at 17:11:21.8 ut, 78.0 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 250.05464, -34.00719 which is equivalent to: ra(j2000) = 16h 40m 13.11s dec(j2000) = -34d 00' 25.9" with an uncertainty of 3.6 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 http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (3.35 x 10^21 cm^-2, willingale et al. 2013), with an excess column of 3.2 (+2.68/-2.37) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 2.95e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 88 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. no correction has been made for the expected extinction corresponding to e(b-v) of 0.54. 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 190821a: swift detection of a burst |
the distribution of jet angles for short gamma-ray bursts (sgrbs) is critical to constrain because it directly affects the true energy scale and event rate. the event rate is of particular interest in the gravitational wave era. our current knowledge of the jet angle distribution comes almost exclusively from x-ray observations at >1 day after the burst. here, we propose for chandra too observations to monitor a sgrb afterglow and constrain its collimation, either from the detection of a jet break, or the non-detection of a break to place a lower limit of >5-20 deg. a precise calculation of the jet angle also requires broad-band afterglow observations. with our ongoing radio, and optical too programs, our group is uniquely poised to provide the tightest constraints on the jet angle. | the late-time x-ray behavior of short gamma-ray bursts: implications for energetics and rates |
the vla sky survey (vlass) is an ongoing project by the nrao to map ~34,000 deg2 of the sky at 3ghz, over 3 epochs spanning 6 years. in preparation for the full survey, a set of fields covering 2480 deg2 was recently observed as the vlass pilot project. we searched 1333 deg2 of the vlass pilot for radio transients with characteristic decay timescales between weeks and years, such as the synchrotron afterglows of supernovae, tidal disruption events, and long/short gamma ray bursts. these radio afterglows are thought to be roughly isotropic and extinction-free, allowing us to observe transients that would be missed by optical/high energy surveys due to obscuration or off-axis jetting.within the searched area, we identified 215 vlass sources that have no counterpart in the first survey and have a projected distance of < 50kpc from the nearest galaxy by angular distance in the clu and gwens galaxy catalogs. by selection, these targets are predominently located near low redshift (z < 0.05) galaxies, allowing us to study their host environments with a sub-kiloparsec spatial resolution. prioritizing based on visual association with sdss galaxies, we imaged and/or took spectra of the host environment of 60 targets with the low resolution imaging spectrometer (lris) on keck 1. in this talk, we present the radio and optical results for the most exciting vlass transients. | radio transients in 1333 deg2 of the vla sky survey pilot |
gamma ray bursts (grbs) are the most luminous explosions in the universe. these electromagnetic explosions produce jets demonstrated by a short burst of prompt gamma-ray emission followed by a broadband afterglow. there are sharp increases of flux in the x-ray light curves known as flares that occurs in about 50% of the afterglows. in this study, we characterized all of the x-ray afterglows that were detected by the swift x-ray telescope (xrt), whether with flares or without. we fit flares to the norris function (norris et al. 2005) and power laws with breaks where necessary (racusin et al. 2009). after fitting the norris function and power laws, we search for the residual pattern detected in prompt grb pulses (hakkila et al. 2014, 2015, 2017), that may indicate a common signature of shock physics. if we find the same signature in flares and prompt pulses, it provides insight into what causes them, as well as, how these flares are produced. | gamma-ray burst x-ray flares light curve fitting |
we observed the field of grb 180620a (swift trigger 843211; evans et al., gcn #22807) simultaneously in g'r'i'z'jhk with grond (greiner et al. 2008, pasp 120, 405) mounted at the 2.2 m mpg telescope at eso la silla observatory (chile). observations started at 04:35 ut on 2018-06-21, 20 hours after the grb trigger. they were performed at an average seeing of 1.4" and at an average airmass of 1.7. we detect a faint point source consistent with the position of the reported x-ray and optical afterglow (elenin et al., gcn #22800; osborne et al., gcn #22802; breeveld et al., gcn #22805). based on a total exposures time of around 30mins we estimate the following ab magnitudes: g' = 23.9 +/- 0.1 mag r' = 23.4 +/- 0.1 mag i' = 23.1 +/- 0.1 mag z' > 23.2 mag j > 21.2 mag h > 20.5 mag k > 19.3 mag given magnitudes are calibrated against panstarrs and 2mass field stars and are not corrected for the expected galactic foreground extinction corresponding to a reddening of e_(b-v)=0.11 in the direction of the burst (schlafly & finkbeiner 2011). we thank markus rabus for the excellent support from la silla. | grond observations of grb 180620a |
short duration gamma-ray bursts (grbs) are brief flashes of gamma-ray radiation followed by a longer lasting, broadband (from radio to x-rays) afterglow emission. nasa's swift mission provided breakthrough observations connecting these high-energy transients to the coalescence of two compact objects. short grbs are therefore prime candidate electromagnetic counterparts of gravitational wave sources detected by advanced ligo and virgo. we carried out a systematic observing campaign of short grbs aimed at characterizing their x-ray emission in order to 1) constrain the jet collimation and the true rate of events; 2) test the possible presence of isotropic emission components, not related to the standard afterglow emission. we present our preliminary results and discuss their implications for the follow-up of future gw detections. | an x-ray view of short duration gamma-ray bursts |
at 11:11:51 ut, the swift burst alert telescope (bat) triggered and located grb 180630a (trigger=845443). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 48.810, -87.482 which is ra(j2000) = 03h 15m 14s dec(j2000) = -87d 28' 54" 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 ~6500 counts/sec (15-350 kev), at ~4 sec after the trigger. the xrt began observing the field at 11:13:13.4 ut, 81.6 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 48.95887, -87.47850 which is equivalent to: ra(j2000) = 03h 15m 50.13s dec(j2000) = -87d 28' 42.6" with an uncertainty of 3.7 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 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 1.34 x 10^21 cm^-2 (willingale et al. 2013). the initial flux in the 2.5 s image was 6.12e-10 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 87 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 03:15:56.02 = 48.98342 dec(j2000) = -87:28:42.4 = -87.47844 with a 90%-confidence error radius of about 0.62 arc sec. this position is 5.7 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.44 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.13. burst advocate for this burst is p. d'avanzo (paolo.davanzo at brera.inaf.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/too.html.) | grb 180630a: swift detection of a burst with an optical counterpart |
the 60 cm bootes-5/javier gorosabel telescope at observatorio astronómico nacional in san pedro mártir (méxico) automatically responded to the swift trigger of grb 170519a (ukwatta et al., gcn 21106). the first unfiltered images (60 s exposures) were obtained at 05:15:08.9 ut (5 min after the burst). at the position of the swift x-ray afterglow, we confirm the optical afterglow detected by uvot, at a magnitude of 16.6+/-0.1 when compared to the gsc2.3 catalog, and fading during the late-time bootes-5/jgt observation. we thank the staff at observatorio astronómico nacional in san pedro mártir for its excellent support. [gcn ops note(19may17), at the request of the author, the last 3 authors were added.] | grb 170519a: bootes-5/jgt early optical detection |
synchrotron radiation from shock accelerated electrons has been well established as the source of the broadband afterglow emission accompanying gamma-ray bursts (grbs). the relativistic electrons producing this emission are expected to also produce synchrotron self-compton (ssc) emission, yet no convincing evidence has ever been found for such an emission component. late-time detections at gev energies by the fermi large area telescocpe (lat) have been shown to be consistent with the high energy extension of afterglow emission, without the need for ssc to explain most lat detections. the detection of very high energy emission in grb 190114c by fermi lat and magic is now the first conclusive detection of this elusive emission component and may shed further light on the physics of grb afterglows. we will review the fermi gamma-ray burst monitor (gbm) and lat observations of grb 190114c and discuss their implications for relativistic shock physics, future very high energy observatories, and possible constraints on the extra-galactic background light. | fermi observations of high energy emission from grb 190114c |
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 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 |
from the comprehensive statistical analysis of swift x-ray light-curves collected from the launch of the swift satellite until the end of 2010, we found a three-parameter correlation between the isotropic energy emitted in the rest frame 1-104 kev energy band during the prompt emission (eγ,iso), the rest frame peak of the prompt emission energy spectrum (epk), and the x-ray energy emitted in the rest frame 0.3-30 kev observed energy band (ex,iso), computed excluding the contribution of the flares. the importance of this scaling law is that it is followed by both long and short grbs, and, at the same time, involves prompt and afterglow emission quantities. therefore there are some properties which are shared by long and short grbs as a whole. we updated this correlation considering all grbs observed until june 2014, confirming the existence of this scaling law, and examining some particular grbs, as 090426 and 100816a. we also discuss the physics that is driving this correlation. | ten years of swift: a universal scaling for short and long gamma-ray bursts (ex,iso - eγ,iso - epk) |
gamma-ray bursts are exploding massive stars and some of the most luminous explosions in the universe. they can serve as powerful light houses that probe the structure and abundances of the dense ism in their hosts at almost any redshift and not accessible by other types of observations, e.g. using quasars. since 2009 our collaboration has collected uv to nir medium-resolution spectra of over 70 grb afterglows using the eso/vlt x-shooter spectrograph. our sample covers a redshift range from 0.06 to 6.3 allowing us to study the dynamics of the ism in star-forming galaxies from the nearby universe out to the epoch of reionization and for the first time in a statistically sound way. absorption lines usually show a rich structure of different components due to galaxy dynamics, turbulences or in-/outflows and different ionization levels seem to arise from different regions in the host. fine-structure lines some of which are uniquely observed in grb hosts are excited in the dense regions close to the grb site itself. for some host with z < 3 we can also simultaenously observe emission lines from the hot ism, comparing the origin of hot and cold gas within the same galaxy. the large wavelength coverage of the sample gives us the unique opportunity to study the evolution of gas dynamics across most of the time galaxies have existed, how the gas structure changed over time and what is the importance and consistency of in- and ouflows. here we will present the x-shooter grb afterglow sample, our results on the study of absorption and emission line features and compare the observed structures with theoretical models of galaxies to get a unique insight on the distrubution and dynamics of the ism in starforming galaxies at any redshift. | structure and dynamics of star-forming galaxies across the history of the universe using grbs |
at 09:45:20 ut, the swift burst alert telescope (bat) triggered and located grb 190701a (trigger=912310). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 28.063, +58.906 which is ra(j2000) = 01h 52m 15s dec(j2000) = +58d 54' 23" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 100 sec. the peak count rate was ~800 counts/sec (15-350 kev), at ~37 sec after the trigger. the xrt began observing the field at 09:47:41.9 ut, 141.1 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source located at ra, dec 28.08019, 58.91005 which is equivalent to: ra(j2000) = 01h 52m 19.25s dec(j2000) = +58d 54' 36.2" with an uncertainty of 3.7 arcseconds (radius, 90% containment). this location is 35 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 6.36 x 10^21 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. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 100% of the xrt error circle. the typical 3-sigma upper limit has been about 19.6 mag. the 8'x8' region for the list of sources generated on-board covers 100% of the xrt error circle. the list of sources is typically complete to about 18 mag. no correction has been made for the large, but uncertain, extinction expected. burst advocate for this burst is t. n. ukwatta (tilan.ukwatta 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 190701a: swift detection of a burst |
at 14:15:23 ut, the swift burst alert telescope (bat) triggered and located grb 191106a (trigger=933515). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 269.350, +46.052, which is ra(j2000)c = 17h 57m 24s dec(j2000) = +46d 03' 06" 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 5 sec. the peak count rate was ~2800 counts/sec (15-350 kev), at ~0 sec after the trigger. the xrt began observing the field at 14:16:34.2 ut, 70.3 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 269.3349, 46.0346 which is equivalent to: ra(j2000) = 17h 57m 20.38s dec(j2000) = +46d 02' 04.7" with an uncertainty of 2.4 arcseconds (radius, 90% containment). this location is 73 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (4.38 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 4 (+4.05/-3.32) x 10^21 cm^-2 (90% confidence). uvot took a finding chart exposure of 250 seconds with the u filter starting 130 seconds after the bat trigger. no credible afterglow candidate has been found in the initial data products. the 2.7'x2.7' sub-image covers 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 0.06. burst advocate for this burst is f. e. marshall (marshall at milkyway.gsfc.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 191106a: swift detection of a burst |
svom is a french-chinese space mission to be launched in 2021, whose goal is the study of gamma-ray bursts, the most powerful stellar explosions in the universe. the micro-channel x-ray telescope (mxt) is an x-ray focusing telescope, on board svom, with a field of view of 1 degree (working in the 0.2-10 kev energy band), dedicated to the rapid follow-up of the gamma-ray bursts counterparts and to their precise localization (smaller than 2 arc minutes). in order to reduce the optics mass and to have an angular resolution of few arc minutes, a "lobster-eye" configuration has been chosen. using a numerical model of the mxt point spread function (psf) we simulated mxt observations of point sources in order to develop and test different localization algorithms to be implemented on board mxt. we included preliminary estimations of the instrumental and sky background. the algorithms on board have to be a combination of speed and precision (the brightest sources are expected to be localized at a precision better than 10 arc seconds in the mxt reference frame). we present the comparison between different methods such as barycentre, psf fitting in one or two dimensions. the temporal performance of the algorithms is being tested using the x-ray afterglow data base of the xrt telescope on board the nasa swift satellite. | localization algorithms for micro-channel x-ray telescope on board svom space mission |
we present a correlation observed in both the optical and x-ray afterglows of long duration gamma-ray bursts (grbs), between the initial luminosity (measured at restframe 200s) and average afterglow decay rate. this correlation does not depend on the presence of specific light curve features and is potentially applicable to all long grb afterglows. we explore how the correlation parameters from the optical and x-ray bands relate to each other and to the prompt emission phase. we will also explore the implications and test if the observations are consistent with the expectations of the standard afterglow model. | exploring the behaviour of long gamma-ray bursts with intrinsic afterglow correlations |
swift-xrt has performed follow-up observations of the fermi/lat-detected burst grb 170522a (arimoto et al. gcn circ. 21127) in a series of observations tiled on the sky. the total exposure time is 4.7 ks, distributed over 5 tiles; the maximum exposure at a single sky location was 3.3 ks. the data were collected between t0+39.4 ks and t0+51.3 ks, and are entirely in photon counting (pc) mode. four uncatalogued x-ray sources have been detected, however none of them is above the rass limit or shows definitive signs of fading. therefore, at the present time we cannot identify which, if any, is the afterglow. details of these sources are given below: source 1: ra (j2000.0): 139.1534 = 09:16:36.82 dec (j2000.0): +25.4844 = +25:29:03.9 error: 3.8 arcsec (radius, 90% conf. [enhanced position]) count-rate: (9.7 [+3.1, -2.6])e-3 ct s^-1 distance: 901 arcsec from fermi/lat position. flux: (4.2 [+1.3, -1.1])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 139.2381 = 09:16:57.13 dec (j2000.0): +25.4737 = +25:28:25.5 error: 6.0 arcsec (radius, 90% conf.) count-rate: (6.7 [+3.3, -2.5])e-3 ct s^-1 distance: 780 arcsec from fermi/lat position. flux: (4.4 [+2.2, -1.6])e-13 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 3: ra (j2000.0): 139.1099 = 09:16:26.38 dec (j2000.0): +25.8756 = +25:52:32.2 error: 6.5 arcsec (radius, 90% conf.) count-rate: (6.6 [+2.9, -2.2])e-3 ct s^-1 distance: 1050 arcsec from fermi/lat position. source 4: ra (j2000.0): 139.0535 = 09:16:12.85 dec (j2000.0): +25.6179 = +25:37:04.5 error: 10.2 arcsec (radius, 90% conf.) count-rate: (5.6 [+3.1, -2.3])e-3 ct s^-1 distance: 948 arcsec from fermi/lat position. the results of the xrt-team automatic analysis of the tiled xrt observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/xrt_products/tiled_grb00068. this circular is an official product of the swift-xrt team. | grb 170522a: swift-xrt observations |
at 02:45:47 ut, the swift burst alert telescope (bat) triggered and located grb 170705a (trigger=760064). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 191.705, +18.293 which is ra(j2000) = 12h 46m 49s dec(j2000) = +18d 17' 35" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve showed a multi-peaked structure with a duration of about 40 sec. the peak count rate was ~17000 counts/sec (15-350 kev), at ~13 sec after the trigger. the xrt began observing the field at 02:46:59.3 ut, 72.3 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 191.70472, 18.30811 which is equivalent to: ra(j2000) = 12h 46m 49.13s dec(j2000) = +18d 18' 29.2" with an uncertainty of 3.8 arcseconds (radius, 90% containment). this location is 54 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the galactic value (1.46 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 4.6 (+3.03/-2.52) x 10^21 cm^-2 (90% confidence). the initial flux in the 2.5 s image was 1.57e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 81 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 12:46:48.97 = 191.70406 dec(j2000) = +18:18:26.2 = 18.30727 with a 90%-confidence error radius of about 0.76 arc sec. this position is 3.7 arc sec. from the center of the xrt error circle. the estimated magnitude is 18.65 with a 1-sigma error of about 0.15. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. burst advocate for this burst is r. l. c. starling (rlcs1 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 170705a: swift detection of a burst with an optical counterpart |
at 05:10:02 ut, the swift burst alert telescope (bat) triggered and located grb 170519a (trigger=753445). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 163.450, +25.378 which is ra(j2000) = 10h 53m 48s dec(j2000) = +25d 22' 41" 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 ~1500 counts/sec (15-350 kev), at ~3 sec after the trigger. the xrt began observing the field at 05:11:23.2 ut, 80.4 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 163.42823, 25.37377 which is equivalent to: ra(j2000) = 10h 53m 42.78s dec(j2000) = +25d 22' 25.6" with an uncertainty of 4.8 arcseconds (radius, 90% containment). this location is 72 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. the initial flux in the 2.5 s image was 3.58e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 91 seconds after the bat trigger. there is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at ra(j2000) = 10:53:42.46 = 163.42693 dec(j2000) = +25:22:27.4 = 25.37429 with a 90%-confidence error radius of about 0.75 arc sec. this position is 1.4 arc sec. from the center of the xrt error circle. the estimated magnitude is 17.07 with a 1-sigma error of about 0.14. no correction has been made for the expected extinction corresponding to e(b-v) of 0.03. burst advocate for this burst is t. n. ukwatta (tilan.ukwatta 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/too.html.) | grb 170519a: swift detection of a burst with an optical counterpart |
a class of long gamma-ray bursts (grbs) with a plateau phase in their x-ray afterglows obeys a three-dimensional (3d) relation (dainotti et al. 2016), between the rest-frame time at the end of the plateau, ta, its corresponding x-ray luminosity, la, and the peak luminosity in the prompt emission, lpeak. we extended the original analysis with x-ray data from july 2014 to july 2016 achieving a total sample of 183 swift grbs with afterglow plateaus and known redshifts. we added the most recent grbs to the previous ‘gold sample’ (now including 45 grbs) and obtained a relation plane with intrinsic scatter compatible within one σ with the previous result. we compared several grb categories, such as short with extended emission, x-ray flashes, grbs associated with sne, long-duration grbs, and the gold sample, composed only by grbs with light curves with good data coverage and relatively flat plateaus and evaluated their relation planes. we found that they are not statistically different from the fundamental plane derived from the gold sample and that the fundamental plane still has the smallest scatter. we compared the jet opening angles tabulated in literature with the angles derived using the eiso-egamma relation of the method in pescalli et al. (2015) and calculated the relation plane for a sample of long grbs accounting for the different jet opening angles. we observed that this correction does not significantly reduce the scatter. in an extended analysis, we found that the fundamental plane is independent from several prompt and afterglow parameters. | a study of the gamma-ray burst fundamental plane |
we review the current observational and theoretical status of the polarization measurements of gamma-ray bursts at all wavelengths. gamma-ray bursts are thought to be produced by an ultra-relativistic jet, possibly powered by a black hole. one of the most important open point is the composition of the jet: the energy may be carried out from the central source either as kinetic energy (of baryons and/or pairs), or in electromagnetic form (poynting flux). the polarization properties are expected to help disentangling main energy carrier. the prompt emission and afterglow polarization are also a powerful diagnostic of the jet geometry. | gamma-ray bursts polarization |
we investigate nucleosynthesis inside the gamma-ray burst (grb) accretion disks formed by the type ii collapsars and outflows launched from these disks. we deal with accretion disks having relatively low accretion rates: 0.001m_ ⊙ s^{ - 1} ≲ dot m ≲ 0.01m_ ⊙ s^{ - 1} and hence they are predominantly advection dominated. we report the synthesis of several unusual nuclei like 31p, 39k, 43sc, 35cl and various isotopes of titanium, vanadium, chromium, manganese and copper in the disk. we also confirm that isotopes of iron, cobalt, nickel, argon, calcium, sulphur and silicon get synthesized in the disk, as shown by previous authors. much of these heavy elements thus synthesized are ejected from the disk and survive in the outflows. indeed, emission lines of many of these heavy elements have been observed in the x-ray afterglows of several grbs. | nucleosynthesis in the gamma-ray burst accretion disks and associated outflows |
we present two very rare cases of short grbs with a shallow decay phase in the optical afterglow: grb 130912a and grb 150424a. we interpret the light curves and seds in the context of the fireball model. | grb 130912a and grb 150424a: two short gamma ray bursts with a plateau phase in the optical after-glow challenge the compact binary merger scenario |
as the universe's most luminous transient events, long gamma-ray bursts (grbs) are observed at cosmological distances. the afterglow emission generated by the burst's interaction with the surrounding medium presents the opportunity to study the local environment, as well as intervening systems. the transient nature of these events requires observations starting within minutes of the grb to maximize the scientific opportunities.this dissertation work comprises efforts to advance the field with a new instrument, the rapid infrared imager and spectrograph (rimas). the optical design is complicated by the broad band coverage (0.97 to 2.39 microns) and the necessity of transmissive optics due to space and weight limitations on the telescope. additionally, the entire optical system must be cooled to cryogenic temperatures to decrease the background from thermal emission. the completed instrument will be permanently installed on lowell observatory's new 4.3 meter discovery channel telescope (dct) located in happy jack, arizona. the fast slew time of the telescope, combined with the instrument's ability to image in two bands simultaneously and switch to spectroscopic configurations in under a minute will allow observers to obtain photometric data within minutes and spectra within ~ ten minutes.in addition to instrumentation work on rimas's optics, early time photometric light curves have been studied primarily using data from the reionization and transients infrared/optical project (ratir). early time photometric data in six optical and near-infrared (nir) bands has allowed a study of color evolution in the early to late time seds. this study probes possible impacts of the grb on the local medium as well as intrinsic changes in the afterglow emission.this work is made possible by the ratir and rimas collaborations as well as financial support by the nsf. | fast-response optical and near-infrared grb science with ratir and rimas |
gamma ray burst (grb's), extremely energetic flashes of gamma rays, are caused by either deaths of massive unstable stars or colliding binary neutron stars. a unique burst, grb 150518a, had two recorded bursts fifteen minutes apart which is very rare and is considered to be ultra-long, lasting around thirty minutes total and is associated with a supernova explosion. gbr 150518a is also extremely close compared to the average burst being measured to have a redshift of .2, this is important to note because grb's measuring less than a redshift of .3 only are seen every ten years. gamma rays are emitted by supernovae, neutron stars, black holes, and quasars and by studying grb's it allows us to see more deeply into how these objects function. the first few days of grb 150518as' detected afterglow was plotted in different wavelengths, including optical, x-ray, radio, and infrared, in flux verses time. data is continuously being added as time goes on. this research is funded by the nsf, grant number 1358990. | gamma ray burst 150518a measured at different wavelengths |
gamma-ray bursts (grbs) are the most luminous events in the universe with egamma,iso ∼ 1048-54 erg. leading models hypothesize that grbs are created from inter- nal collisions within collimated and ultrarelativistic jets. the jets then shock-heat the surrounding material (e.g. interstellar medium) to create grb afterglows. these afterglows are extremely useful probes of the universe because long grbs are (1) bright events that can be used as backlights for absorption studies, (2) able to probe at all redshifts massive stars exist, and (3) transient events that allow us to follow- up on the host galaxies at late times. in this thesis we study the environments of grbs. we first explore the relationship between grb and supernova (sn) using a nearby grb-sn (grb 130702a/sn 2013dx) at z = 0.145. there are only nine other grb-sne that were close enough to have extensive spectroscopic and photometric follow-up of the sn at late times. we create a quasi-bolometic light curve of sn 2013dx and fit an analytical equation to the quasi-bolometric light curve combined with measurements of the photospheric velocity to determine sn parameters: mass of 56ni, kinetic energy, and ejecta mass. we examine the relationship between sn parameters and e gamma,iso for the 10 well-studied grb-sne, but find no correlations despite numerical simulation predictions that the mass of 56ni should correlate with the degree of asymmetry. we then move to larger distance scales and use grb afterglows as bright back- lights to study distant galaxies. we examine the galactic environments of damped lyman-alpha systems (dlas; nhi ≥ 1020.3 cm-2 ) identified with grb afterglows at z ∼ 2 - 6. we use late-time photometry after the grb afterglow has faded to determine star formation rates (sfrs) from rest-frame ultraviolet measurements or spectral energy distribution (sed) models from multiband photometry. we com- pare our sample's sfrs to a sample of quasars (qsos) dla host galaxies. despite the overlapping nhi and redshift ranges, our grb-dla galaxies have much larger sfrs than the qso-dla host galaxy sample; this may suggest that the qso-dla and grb-dla galaxy populations are different. we also compare star formation efficiencies to the local universe and simulations at z = 3. a large portion of this thesis has focused on the development of a new ground- based grb afterglow follow-up instrument, the rapid infrared imager-spectrometer (rimas), that will target high-redshift grb afterglows to study early galaxy envi- ronments. rimas covers 0.97-2.37 mum and can simultaneously observe two band-passes in any observing mode: photometry, low-resolution spectroscopy (r ∼ 30), or high-resolution spectroscopy (r ∼ 4000). in particular, this thesis focuses on rimas's three detectors: two science grade teledyne hgcdte astronomy wide area infrared imager with 2k x 2k, reference pixels and guide mode (h2rg) and a slit-viewer spitzer legacy indium-antimonide (insb) array. we describe the detector hardware and characterization in detail and discuss general infrared detector troubleshooting methods at both cryogenic and room temperatures. several software packages have been developed for rimas throughout this thesis work. we introduce rimas's quick reduction pipeline that takes raw images from a single acquisition and returns a single result frame. we then present a generalized data reduction pipeline that we have tested on two currently operational photometers. we also describe our detailed and realistic rimas throughput models for all three observing modes as well as our online observer calculators with these throughput models. all of our data products are open source and are publicly available on github repositories with detailed documentation. | gamma-ray bursts: lighting up the high-redshift universe |
swift-xrt has performed follow-up observations of the maxi-detected burst grb 190804b (sato et al. gcn circ. 25262) 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 395 s. the data were collected between t0+37.2 ks and t0+38.6 ks, and are entirely in photon counting (pc) mode. two uncatalogued x-ray sources have been detected, however none of them is above the rass limit or shows definitive signs of fading. therefore, at the present time we cannot identify which, if any, is the afterglow. details of these sources are given below: source 1: ra (j2000.0): 239.7568 = 15:59:1.62 dec (j2000.0): -44.6361 = -44:38:09.8 error: 4.1 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.031 [+0.014, -0.011] ct s^-1 distance: 606 arcsec from maxi position. flux: (1.38 [+0.60, -0.46])e-12 erg cm^-2 s^-1 (observed, 0.3-10 kev) source 2: ra (j2000.0): 240.0251 = 16:00:6.02 dec (j2000.0): -44.7816 = -44:46:53.9 error: 3.9 arcsec (radius, 90% conf. [enhanced position]) count-rate: 0.113 [+0.038, -0.031] ct s^-1 distance: 333 arcsec from maxi position. flux: (5.1 [+1.7, -1.4])e-12 erg cm^-2 s^-1 (observed, 0.3-10 kev) 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_grb00082. this circular is an official product of the swift-xrt team. | grb 190804b: swift-xrt observations |
at 09:52:16 ut, the swift burst alert telescope (bat) triggered and located grb 190926a (trigger=926515). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 100.599, +59.511 which is ra(j2000) = 06h 42m 24s dec(j2000) = +59d 30' 40" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). since this is an image trigger, the bat light curve showed no significant structure. the xrt began observing the field at 09:54:30.4 ut, 134.0 seconds after the bat trigger. xrt found a bright, uncatalogued x-ray source located at ra, dec 100.5699, 59.5292 which is equivalent to: ra(j2000) = 06h 42m 16.78s dec(j2000) = +59d 31' 45.1" with an uncertainty of 4.8 arcseconds (radius, 90% containment). this location is 84 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 5.87e-09 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 144 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 0.06. burst advocate for this burst is a. melandri (andrea.melandri at brera.inaf.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 190926a: swift detection of a burst |
since the historic aug. 17, 2017 simultaneous detection of gravitational and electromagnetic waves produced by the merger of two neutron stars, the gw-grb 170817 event, interest in short gamma-ray bursts (sgrbs) has increased exponentially. sgrbs (bursts with durations less than 2.0 seconds) represent only about 10 % of all bursts, and unlike long grbs, there was until this recent event no complete consensus on the (merger) physical mechanism responsible for sgrbs. this combined fact had kept interest toward short bursts relatively low. but in the few years before the gw-grb connection, which fully cemented the merger model as the physical process behind sgrbs, the detection of kilonovae/macronovae associated with three sgrbs had already started to raise the interest in this class of bursts.fong et al. (2015) collected and analyzed afterglow observations of sgrbs from 2005 to 2014, covering their broadband emission from x-rays to radio. using the widely adopted theoretical prescription of panaitescu & kumar (2000) for calculating afterglow fluxes, fong et al. (2015) extracted individual and statistical values for the bursts' and afterglows' physical parameters: kinetic energy, medium density, electron and magnetic energy fractions, and jet opening angles. we have extended that work to the last 3 years (jan. 2015 to dec. 2017), using swift events (29 short bursts recorded during that period) and fermi events (116 events). we have searched the literature (gcn reports and published papers) to collect afterglow observations, whether positive or negative (upper limits), limiting ourselves to optical and near-infrared data, the bands where kilonova detections can be successful.our aim is to fit or constrain the afterglow light curves with physical parameters, to the extent possible, and to try to identify cases that most resemble those that have had a kilonova detection.we present the most interesting cases that we have uncovered, along with the physical results from the sample. | analysis of recent short grb afterglow light curves |
at 14:46:39 ut, the swift burst alert telescope (bat) triggered and located grb 190824a (trigger=922107). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 215.329, -41.902, which is ra(j2000) = 14h 21m 19s dec(j2000) = -41d 54' 07" 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 120 sec. the peak count rate was ~3200 counts/sec (15-350 kev), at ~1 sec after the trigger. the xrt began observing the field at 14:55:24.0 ut, 524.4 seconds after the bat trigger. using promptly downlinked data we find a fading, uncatalogued x-ray source with an enhanced position: ra, dec 215.3045, -41.8943 which is equivalent to: ra(j2000) = 14h 21m 13.09s dec(j2000) = -41d 53' 39.3" with an uncertainty of 2.3 arcseconds (radius, 90% containment). this location is 71 arcseconds from the bat onboard position, within the bat error circle. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. no spectrum from the promptly downlinked event data is yet available to determine the column density. uvot took a finding chart exposure of 150 seconds with the white filter starting 568 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 0.12. burst advocate for this burst is v. d'elia (delia at ssdc.asi.it). please contact the ba by email if you require additional information regarding swift followup of this burst. in extremely urgent cases, after trying the burst advocate, you can contact the swift pi by phone (see swift too web site for information: http://www.swift.psu.edu/) | grb 190824a: swift detection of a burst |
with the discovery of the first binary neutron star (bns) merger (gw170817) and its electromagnetic counterpart, grb 170817a and the subsequent kilonova and afterglow, we have fully entered the multi-messenger era of astrophysics. using the burst and transient source experiment (batse) and swift-burst alert telescope (bat) catalog of gamma-ray bursts (grbs), we propose to search for events that are similar to grb 170817a, the only confirmed bns counterpart to date. we will investigate past grbs to better understand the physics that links bns mergers to short grbs. grb 170817a was a relatively faint but ordinary short grb in the fermi-gbm sample. because of the high effective area, batse is better suited to identify faint grbs than any other instrument. swift grbs, while fewer in number, have the promise of adding invaluable afterglow information. since fermi-gbm and swift overlap, joint detection of twins of grb 170817a, will be particularly revealing. we present an iterative method to identify grbs similar to grb 170817a. our initial exploratory searches reveal convincing candidates for all three instruments effectively guaranteeing exciting results. we will derive rates, trends among the twin grbs, provide a detailed analysis and test current models for bns merger counterparts. | gamma-ray bursts similar to grb 170817a: comprehensive search in the batse and swift data |
the discovery of gravitational waves resulting from the merger of two massive black holes (gw150914) has revolutionized our view of merging compact binaries. more recently, the swope supernova survey of the optical counterpart of a gravitational wave event in the ngc 4993 galaxy, gw170817, emanating from the merger of two neutron stars, has triggered a lot of research work. emphasis has been on comparing the existing theoretical models with the observational data, allowing for the prospect of an even more stringent test of general relativity. the afterglow of this event was observed in a wide range of wavelengths extending from radio waves to gamma rays. in this work, we first explore the evolutionary pathways of compact binary systems following the in-spiral, merger, and ring down sequence. we then proceed to discuss the processes leading to the production of gravitational waves and electromagnetic emission resulting from the merger of compact objects, particularly neutron star binaries and neutron star_black hole systems. we construct a basic inventory of the energy released during the merger of compact binaries in all bands of the electromagnetic spectrum with emphasis on gamma-ray burst emission. the constraints on certain wavelength emissions, such as gamma-ray bursts, are discussed in terms of orbital dynamical instabilities, energy transfer processes, and possible jet orientations with respect to the observer. | merger of compact binaries in the context of gravitational waves and short-lived gamma-ray bursts |
at 00:01:19 ut, the swift burst alert telescope (bat) triggered and located grb 191228a (trigger=946476). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 5.339, -8.670, which is ra(j2000) = 00h 21m 21s dec(j2000) = -08d 40' 12" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). the bat light curve is typically plain for an image trigger. the xrt began observing the field at 00:03:23.2 ut, 123.4 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 5.34755, -8.68313 which is equivalent to: ra(j2000) = 00h 21m 23.41s dec(j2000) = -08d 40' 59.3" with an uncertainty of 3.7 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 in excess of the galactic value (3.80 x 10^20 cm^-2, willingale et al. 2013), with an excess column of 4.4 (+5.17/-3.93) x 10^21 cm^-2 (90% confidence). the initial flux in the 0.1 s image was 1.26e-08 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 0.04. 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 191228a: swift detection of a burst |
at 14:57:15 ut, the swift burst alert telescope (bat) triggered and located grb 190604b (trigger=906654). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 297.587, -32.932 which is ra(j2000) = 19h 50m 21s dec(j2000) = -32d 55' 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 250 sec, with two major peaks at ~t0 and ~t+155 s. the peak count rate was ~4000 counts/sec (15-350 kev), at ~155 sec after the trigger. the xrt began observing the field at 14:59:12.5 ut, 116.8 seconds after the bat trigger. using promptly downlinked data we find a bright, variable uncatalogued x-ray source located at ra, dec 297.53804, -32.97663 which is equivalent to: ra(j2000) = 19h 50m 09.13s dec(j2000) = -32d 58' 35.9" with an uncertainty of 3.6 arcseconds (radius, 90% containment). this location is 218 arcseconds from the bat onboard position. this position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. a power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the galactic value of 1.36 x 10^21 cm^-2 (willingale et al. 2013). the initial flux in the 0.1 s image was 1.11e-08 erg cm^-2 s^-1 (0.2-10 kev). uvot took a finding chart exposure of 150 seconds with the white filter starting 126 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 0.14. 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 190604b: swift detection of a burst |
at 04:07:18 ut, the swift burst alert telescope (bat) triggered and located grb 190613a (trigger=908288). swift slewed immediately to the burst. the bat on-board calculated location is ra, dec 182.559, +67.233 which is ra(j2000) = 12h 10m 14s dec(j2000) = +67d 13' 58" 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 ~500 counts/sec (15-350 kev), at ~10 sec after the trigger. the xrt began observing the field at 04:09:34.8 ut, 136.5 seconds after the bat trigger. using promptly downlinked data we find a bright, uncatalogued x-ray source located at ra, dec 182.53286, 67.23489 which is equivalent to: ra(j2000) = 12h 10m 07.89s dec(j2000) = +67d 14' 05.6" with an uncertainty of 4.0 arcseconds (radius, 90% containment). this location is 37 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. the initial flux in the 2.5 s image was 1.18e-09 erg cm^-2 s^-1 (0.2-10 kev). 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 list of sources generated on-board at ra(j2000) = 12:10:07.01 = 182.52919 dec(j2000) = +67:14:07.0 = 67.23528 with a 90%-confidence error radius of about 1.10 arc sec. this position is 9.9 arc sec. from the center of the xrt error circle. the estimated magnitude is 18.28. no correction has been made for the expected extinction corresponding to e(b-v) of 0.02. 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 190613a: swift detection of a burst with an optical counterpart |
swift has carried out 449 observations of the lvc error region for the gw trigger s191110af, using the 'cwb' gw localisation map. because this was a 'burst' pipeline trigger with a high frequency, observations were weighted towards the galactic plane.the observations currently span from 10 ks to 88 ks after the lvc trigger, and the xrt has covered 53.5 degrees^2 on the sky (corrected for overlaps). this covers 0.441% of the probability in the 'cwb' skymap, and 16% after weighting towards the galactic plane is accounted for. we have detected 11 x-ray sources. each source is assigned a rank of 1-4 which describes how likely it is to be related to the gw trigger, with 1 being the most likely and 4 being the least likely. the ranks are described at https://www.swift.ac.uk/ranks.php. we note that a number of gcn/counterpart notices were issued with ranks 1 or 2; these also all had the warn_flag field set to 1. these were spurious sources caused by stray light from a bright x-ray source outside of the nominal field of view. counterpart notices are automatically produced before any human vetting of the sources has been carried out. after vetting, we have found: * 0 sources of rank 1 * 0 sources of rank 2 * 5 sources of rank 3 * 6 sources of rank 4 for all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with nh=3x10^20 cm^-2, and photon index (gamma)=1.7 the results of the xrt automated analysis are online at https://www.swift.ac.uk/lvc/s191110af this circular is an official product of the swift xrt team. | ligo/virgo s191110af: swift xrt observations, no secure afterglow found |
swift has performed further observations of the field of the maxi/gsc-detected burst grb 190708b (kawabuko et al., gcn 25037). an additional 3.4 ks of data were collected between 5.96 days and 6.11 days after the maxi trigger. source 1, initially reported by tohuvavohu et al. (gcn 25053) as the likely x-ray counterpart, has faded to a level of 2.9e-3 counts/s (1.3e-13 ergs/cm^2/s). source 1 is therefore confirmed as the x-ray afterglow of grb 190708b. this circular is an official product of the swift-xrt team. | grb 190708b: confirmation of the x-ray afterglow |
swift-xrt has performed further follow-up observations of the gbm-detected burst grb 200325b (fermi gbm team, gcn cir. 27441), collecting overall 4.6 ks of photon counting (pc) mode data between t0+102.4 ks and t0+505.5 ks. the uncatalogued x-ray source (source 1) reported in d'avanzo et al. (gcn circ. 27457) has faded with alpha >1.2, confirming that this is the grb afterglow. the results of the xrt-team automatic analysis of the afterglow are at https://www.swift.ac.uk/too_grbs/00020978/source1.php. the results of the full analysis of the xrt observations are available at https://www.swift.ac.uk/too_grbs/00020978. this circular is an official product of the swift-xrt team. | grb 200325b: further swift-xrt observations |
long grb 190114c, identified on january 14th, 2019, was the first gamma-ray burst that substantially violated the defined 10 gev energy limit of the synchrotron model, with an observed emission between 0.2 - 1 tev and a low redshift of z = 0.425. this paper analyzes its immediate afterglow broadband spectrum from 10$^{17}$ to 10$^{26}$ hz based on observations by the swift x-ray telescope (xrt), fermi gamma-ray burst monitor (gbm), swift burst alert telescope (bat), fermi large area telescope (lat), and major atmospheric gamma imaging cherenkov telescope (magic). we first calculate the physical characteristics necessary to understand the conditions in the burst's emitting region, then conduct temporal and spectral analyses by deriving light curves and spectra using a chain polynomial best-fit in the context of the forward shock model in a homogeneous circumburst density. the spectral energy distributions are found to be double-peaked for t$_0$ + 68-180s, and we show the distribution consists of a distinct synchrotron component followed by an inverse compton component explained by high-energy electrons up-scattering synchrotron photons. we find our calculated bulk lorentz factor = 351 sufficiently explains the peak of the inverse compton component at sub-tev energy levels in the immediate afterglow, and that the comptonization of the burst proceeds in the klein-nishina regime. we conclude this further evidences synchrotron self-compton emission as the mechanism behind the production of very-high-energy photons in grb 190114c. | immediate afterglow physical characteristics and broadband spectra evidence synchrotron self-compton emission as the reason for vhe production in tev grb 190114c |
recent detections of gamma-ray bursts (grbs) at energies above 100 gev demonstrate that imaging atmospheric cherenkov telescopes (iacts) operating in the very-high-energy range (vhe; e > 100 gev) can provide insights into the physics of grbs. by searching for the highest-energy photons emitted by grbs, these telescopes can help answer questions about the particle acceleration and emission processes that occur during both the prompt and afterglow phases of grbs. veritas is a very-high-energy iact array located at the whipple observatory in southern arizona, which has maintained an active grb observing program since mid-2006. in this presentation, we will share some of the recent achievements of the veritas grb follow-up program. we will discuss the development of analysis methods tailored to transient signals, and how the upper limits on the vhe emission obtained from observations of prominent bursts by veritas allowed us to constrain radiation mechanisms in the afterglow (e.g., for grb 130427a) and constrain properties of the environment in which the burst took place (e.g., for grb 150323a). compact binary mergers that trigger short grbs may also result in gravitational wave emission, so we will review both our follow-up program from ligo/virgo triggers, and also the use of archival veritas data to search for short grbs based on sub-threshold events for ligo/virgo. lastly, based on the properties of the vhe-detected grbs, we will discuss recent changes to our follow-up strategy to account for the swift /xrt properties for optimal veritas observing sensitivity. | the veritas gamma-ray burst follow-up program |
we present an observational approach for the independent detection of the prompt optical emission of long gamma-ray bursts (grbs). for this purpose, we explore the potential of the large array survey telescope (last). this array of small optical telescopes can be used to scan a wide region of the sky, and to focus on a smaller field of view with increased sensitivity, as needed. the modularity of the array facilitates dynamic scanning of multiple fields, by shifting telescope pointing directions with high cadence. this can significantly increase the effective sky-coverage of a blind survey on short time scales. for events associated with gamma-ray counterparts, the valuable early-time data can supplement high-energy observations. regardless of gamma-ray association, detections can potentially be used to explore various phenomena associated with grbs, such as orphan afterglows; dirty fireballs; and choked jets. we simulate a sample of grbs and their respective optical signals at early times. after accounting for dynamic cadence, the light curves are given as input to a machine learning classifier, used to identify astrophysical transients. we find that by dedicating half of a last array to a blind search, one would expect to discover 7-11 grbs per year, corresponding to an approximate intrinsic event rate of 0.12 per square degree per year. | detecting the prompt optical flashes of gamma-ray bursts with small telescope arrays |
distinct x-ray plateau and flare phases have been observed in the afterglows of gamma-ray bursts (grbs), and most of them should be related to central engine activities. in this paper, we collect 174 grbs with x-ray plateau phases and 106 grbs with x-ray flares. there are 51 grbs that overlap in the two selected samples. we analyze the distributions of the proportions of the plateau energy eplateau and the flare energy eflare relative to the isotropic prompt emission energy eγ,iso. the results indicate that they well meet the gaussian distributions and the medians of the logarithmic ratios are ~-0.96 and -1.39 in the two cases. moreover, strong positive correlations between eplateau (or eflare) and eγ,iso with slopes of ~0.95 (or ~0.80) are presented. for the overlapping sample, the slope is ~0.80. we argue that most of x-ray plateaus and flares might have the same physical origin but appear with different features because of the different circumstances and radiation mechanisms. we also test the applicabilities of two models, i.e., black holes surrounded by fractured hyperaccretion disks and millisecond magnetars, on the origins of x-ray plateaus and flares. (2 data files). | vizier online data catalog: energies of x-ray plateaus and flares in grbs (yi+, 2022) |
following the swift/bat trigger of grb 201015a (d'elia et al., gcnc 28632), the 0.3m bootes-1b robotic telescope in mazagon (huelva), southern spain, automatically responded to this burst. a series of images were taken starting on 15 oct at 22:50:48ut (35 s after trigger). we confirm the ot reported by master (lipunov et al., gcnc 28633) in our co-added 30x1s clear filter images at a similar epoch (t_mid = 205 s) with 17.0 mag, at a position consistent with the reported swift/xrt x-ray (kennea et al., gcnc 28635) and late-time optical afterglows position reported by not (malesani et al., gcnc 28637) and goto (ackley et al., gcnc 28639). further analysis is ongoing. we thank the staff at inta-cedea for their excellent support. | grb 201015a: bootes-1 early optical afterglow detection |
gamma-ray bursts (grbs) are interesting objects for testing the emission models in highly energetic regimes and are very promising standardizable candles, given their observability at high redshift (up to $z=9.4$) that allows the extension of the hubble diagram much further the limit of supernovae ia (sne ia), the most distant one being at $z=2.26$. in this study, we demonstrate that the fundamental plane relation involving the prompt peak luminosity in x-rays, the x-rays plateau-end luminosity, and the plateau-end rest-frame time is not only a robust benchmark for testing grb emission models like the magnetar but also a promising avenue for high-$z$ cosmology exploration. first, we discuss the connection between the magnetar model and the grb afterglow correlations. second, through the simulation of grbs, we count how many years are needed to achieve the same precision of modern sne ia samples in the estimation of $\omega_{m}$. | the two-dimensional and three-dimensional relations in the plateau emission in multi-wavelengths |
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