GRB210726A

This page lists all entries on GRB210726A in GRBweb

Summary IPN Swift GCN 30523 GCN 30524 GCN 30525 GCN 30534 GCN 30535 GCN 30536 GCN 30537 GCN 30540 GCN 30542 GCN 30543 GCN 30545 GCN 30558 GCN 30658

Summary table
Variable Value Source
T0 19:19:03 UTC GCN_circulars,Swift Det
ra 193.2908° Swift
decl 19.1902° Swift
pos_error 2.72e-04° Swift
T90 0.39 s Swift
T90_start 19:19:03 UTC Swift
fluence 4.50e-08 erg/cm² Swift
redshift 0.3500 GCN_circulars,Fermi GBM Other
T100 0.39 s
GBM_located False
mjd 59421.80489583333 GCN_circulars,Swift Det
IPN table
GRB_name GRB210726A
ra 193.3417°
decl 19.1833°
pos_error 5.00e-02°
Swift table
GRB_name GRB210726A
t_trigger 19:19:03 UTC
ra 193.2908°
decl 19.1902°
pos_error 2.72e-04°
T90 0.39 s
fluence 4.50e-08 erg/cm²
GCN 30523 table
GRB_name GRB210726A
GCN_number 30523
Detection_method Swift Det
t_trigger 19:19:03 UTC
ra 193.3420°
decl 19.1850°
Circular_text TITLE: GCN CIRCULAR NUMBER: 30523 SUBJECT: GRB 210726A: Swift detection of a burst DATE: 21/07/26 19:39:05 GMT FROM: David Palmer at LANL M. G. Bernardini (INAF-OAB), M. A. Baer (PSU), P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), S. Laha (GSFC/UMBC/CRESST), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), M. J. Moss (GWU), K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 19:19:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210726A (trigger=1061687). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 193.342, +19.185 which is RA(J2000) = 12h 53m 22s Dec(J2000) = +19d 11' 05" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a short spike with a tail with a total duration of about ~3 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. This may be a short GRB. The XRT began observing the field at 19:20:03.6 UT, 60.0 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source with an enhanced position: RA, Dec 193.2909, 19.1898 which is equivalent to: RA(J2000) = 12h 53m 09.81s Dec(J2000) = +19d 11' 23.2" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 174 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.73 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.4 (+2.93/-2.51) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 250 seconds with the U filter starting 276 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18.0 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.020. Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini AT brera.inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
GCN 30524 table
GRB_name GRB210726A
GCN_number 30524
Detection_method Swift-XRT Det
ra 193.2909°
decl 19.1903°
Circular_text TITLE: GCN CIRCULAR NUMBER: 30524 SUBJECT: GRB 210726A: Enhanced Swift-XRT position DATE: 21/07/26 21:21:52 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 1692 s of XRT Photon Counting mode data and 1 UVOT images for GRB 210726A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 193.29093, +19.19030 which is equivalent to: RA (J2000): 12h 53m 9.82s Dec (J2000): +19d 11' 25.1" with an uncertainty of 2.4 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN 30525 table
GRB_name GRB210726A
GCN_number 30525
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 30525 SUBJECT: GRB 210726A: CAHA 2.2m telescope optical limit DATE: 21/07/26 22:25:14 GMT FROM: Youdong HU at IAA-CSIC Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia, A. J. Castro-Tirado M. D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), A. Gardini and I. Hermelo (CAHA) on behalf of a larger collaboration, report: Following the detection of GRB210726A by Swift (Bernardini et al. GCNC 30523), we triggered the 2.2m CAHA telescope (+ CAFOS) at the Calar Alto Observatory (Almeria, Spain). A series of i-band images were gathered starting on July 26, 20:23 UT (i.e. 1.07 h post trigger). On the co-added image (15 x 60s), no optical object is detected down to 21.9 mag at the X-ray afterglow position reported by Swift/XRT (Osborne et al. GCNC 30524). We thank the staff at Calar Alto observatory for their excellent support.
GCN 30534 table
GRB_name GRB210726A
GCN_number 30534
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 30534 SUBJECT: GRB 210726A: RATIR Optical Upper Limits and Candidate Host Galaxy DATE: 21/07/27 16:14:25 GMT FROM: Alan M Watson at UNAM Alan M. Watson (UNAM), Eleonora Troja (GSFC), Nat Butler (ASU), Alexander Kutyrev (GSFC), William H. Lee (UNAM), Michael G. Richer (UNAM), Ori Fox (STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz (UCSC), Jesús González (UNAM), Carlos Román-Zúñiga (UNAM), Harvey Moseley (GSFC), Rosa L. Becerra (UNAM), Simone Dichiara (UMD), and Océlotl López (UNAM) report: We observed the field of candidate short GRB 210726A (Bernardini et al., GCN Circ., 30523) with the Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold Johnson Telescope at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2021/07 27.16 to 2021/07 27.22 UTC (8.24 to 9.65 hours after the BAT trigger), obtaining a total of 1.09 hours exposure in the r and i bands. For a source within the enhanced Swift-XRT error circle (Osborne et al., GCN Circ., 30524), in comparison with the SDSS DR9 catalog, we obtain the following upper limits (3-sigma): r > 23.0 i > 22.7 These magnitudes are in the AB system and are not corrected for Galactic extinction in the direction of the GRB. We note that the SDSS galaxy J125309.63+191127.2 is 3.1 arcsec from the enhanced XRT position and just outside the error circle. In our observations, it has r = 22.2 +/- 0.2 and i = 22.2 +/- 0.2, in agreement with the cataloged values. The cataloged photometric redshift is z = 0.35 +/- 0.15. The probability of a chance alignment is approximately 3%. Given this low probability, we suggest that this source might be the host galaxy. Since this GRB appears to be potentially both short and low-redshift, we encourage further observations. We thank the staff of the Observatorio Astronómico Nacional in San Pedro Mártir.
GCN 30535 table
GRB_name GRB210726A
GCN_number 30535
Detection_method Swift-BAT Det
Circular_text TITLE: GCN CIRCULAR NUMBER: 30535 SUBJECT: GRB 210726A: Likely a short burst DATE: 21/07/27 16:59:24 GMT FROM: Aaron Tohuvavohu at U Toronto GRB 210726A, detected by Swift BAT and XRT (GCN 30523) appears likely to be a short burst, despite the real time duration estimate (~3s) reported in the discovery circular using limited data products. The T90 estimate derived from the full downlinked Swift/BAT event data is less than 0.5 seconds. Follow-up is encouraged.
GCN 30536 table
GRB_name GRB210726A
GCN_number 30536
Detection_method Swift-BAT Det
ra 193.3330°
decl 19.2110°
Circular_text TITLE: GCN CIRCULAR NUMBER: 30536 SUBJECT: GRB 210726A: Swift-BAT refined analysis DATE: 21/07/27 19:36:05 GMT FROM: Amy Lien at GSFC D. M. Palmer (LANL), S. D. Barthelmy (GSFC), M. G. Bernardini (INAF-OAB), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210726A (trigger #1061687) (Bernardini et al., GCN Circ. 30523). The BAT ground-calculated position is RA, Dec = 193.333, 19.211 deg which is RA(J2000) = 12h 53m 19.9s Dec(J2000) = +19d 12' 38.9" with an uncertainty of 2.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a short spike that starts at ~T0, peaks at ~T+0.2 s, and ends at ~T+0.4 s. Some tail emission from the raw light curves was mentioned in the original circular (Bernardini et al., GCN Circ. 30523), and this potential weak tail can be seen in the 1-s binned light curve (15-350 keV) as well. However, image analyses from ~T+0.5 s to ~T+2 s do not find any significant detections that are >~ 2 sigma. Therefore, this signal is also consistent with noise fluctuation. T90 (15-350 keV) is 0.39 +- 0.11 sec (estimated error including systematics). The time-averaged spectrum from T-0.00 to T+0.42 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.54 +- 0.47. The fluence in the 15-150 keV band is 4.5 +- 1.1 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T-0.29 sec in the 15-150 keV band is 0.7 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/1061687/BA/
GCN 30537 table
GRB_name GRB210726A
GCN_number 30537
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 30537 SUBJECT: GRB 210726A: Swift-XRT refined Analysis DATE: 21/07/27 19:57:58 GMT FROM: Phil Evans at U of Leicester A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB), T. Sbarrato (INAF-OAB) and M.G. Bernardini report on behalf of the Swift-XRT team: We have analysed 5.9 ks of XRT data for GRB 210726A (Bernardini et al. GCN Circ. 30523), from 79 s to 75.9 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN Circ. 30524). The light curve can be modelled with a power-law decay with a decay index of alpha=1.49 (+0.22, -0.26). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.2 (+/-0.3). The best-fitting absorption column is 3.3 (+1.3, -1.2) x 10^21 cm^-2, in excess of the Galactic value of 1.7 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 3.3 x 10^-11 (5.7 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.3 (+1.3, -1.2) x 10^21 cm^-2 Galactic foreground: 1.7 x 10^20 cm^-2 Excess significance: 4.5 sigma Photon index: 2.2 (+/-0.3) The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01061687. This circular is an official product of the Swift-XRT team.
GCN 30540 table
GRB_name GRB210726A
GCN_number 30540
Detection_method Fermi GBM Other
redshift 0.3500
Circular_text TITLE: GCN CIRCULAR NUMBER: 30540 SUBJECT: Fermi GBM Sub-Threshold Detection of GRB 210726A DATE: 21/07/28 15:21:41 GMT FROM: Peter Veres at UAH P. Veres (UAH) reports on behalf of the Fermi-GBM Team: "Swift-BAT detected GRB 210726A at 19:19:03 UT (GCN 30523). There was no Fermi-GBM onboard trigger around the event. The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals was run from +/-30 s around the BAT trigger time. A transient source was identified whose most significant timescale according to the search is 512 ms, and a location consistent with the Swift-BAT event. The GBM targeted search event was found with the highest significance with a "soft" spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7). The GBM light curve consists of a single peak. The time-averaged spectrum from T0+0.6 s to T0+1.4 s is best fit by a power law function with index -2.03 +/- 0.3 (T0 is 2021-07-26 19:19:03 UT). A power law function with an exponential high-energy cutoff fits equally well, but it is not statistically preferred over the power law; the fit measures the power law index 0.23 +/- 1.67 and the cutoff energy, parameterized as Epeak, is 41 +/- 10 keV. The event fluence (10-1000 keV) in this time interval for the power law with the exponential cutoff is (6.4 +/- 1.7)E-08 erg/cm^2. Using the photometric redshift z=0.35 reported by Watson et al. (GCN 30534), we derive an isotropic equivalent energy in the 1-10,000 keV range of (2.1 +/- 0.5)E+49 erg. This analysis is preliminary. [1] Goldstein et al. 2019 arXiv:1903.12597 "
GCN 30542 table
GRB_name GRB210726A
GCN_number 30542
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 30542 SUBJECT: GRB 210726A: 6 GHz VLA radio upper limit DATE: 21/07/28 22:38:02 GMT FROM: Genevieve Schroeder at Northwestern University G. Schroeder, W. Fong, A. Rouco Escorial, (Northwestern), T. Laskar (U. of Bath), E. Berger (Harvard) report: "We observed the position of short GRB 210726A (Bernardini et al., GCN 30523; Veres et al., GCN 30540; Palmer et al., GCN 30536; Tohuvavohu et al., GCN 30535) with the Karl G. Jansky Very Large Array (VLA) under program 20B-057 (PI: Fong) beginning on 2021 July 27.81 UT (1.00 days post-burst) at a mean frequency of 6 GHz. Based on preliminary analysis, in 1 hour of observations we do not detect any radio emission at or near the position of the XRT afterglow (Osborne et al., GCN 30524) to a 3-sigma limit of 15 microJy. Additional, detailed analysis is ongoing. We thank the VLA staff for quickly approving and executing these observations."
GCN 30543 table
GRB_name GRB210726A
GCN_number 30543
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 30543 SUBJECT: GRB 210726A: Deep CAHA 2.2m limit DATE: 21/07/29 00:01:25 GMT FROM: Alexander Kann at IAA-CSIC D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), A. Gardini, and I. Hermelo (both CAHA) report: We observed the XRT afterglow position (Osborne et al., GCN #30524) of GRB 210726A (Bernardini et al., GCN #30523), classified as a short GRB (Tohuvavohu, GCN #30535; Palmer et al., GCN #30536; Veres, GCN #30540) with CAFOS mounted at the 2.2m Calar Alto telescope (Almeria, Spain), under good conditions but at high airmass, starting July 26, 20:52:13 UT, 1.553 h after the GRB. We obtained 15 x 180 s images in r'. Within the XRT error circle, we do not detect any source down to r' > 24.2 mag (AB magnitude) at 0.081518 d (1.956 h) after the burst, in agreement with but deeper than limits presented by Hu et al., GCN #30525; Watson et al., GCN #30534. Watson et al. suggest an object about 3" away as a possible host-galaxy candidate. We clearly detect this object and measure r' = 22.26 +/- 0.06 mag. This value is in agreement with detections from the PanSTARRS and SDSS surveys, and therefore there is no evidence of excess emission that could be an afterglow superposed on the host galaxy.
GCN 30545 table
GRB_name GRB210726A
GCN_number 30545
Detection_method Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 30545 SUBJECT: GRB 210726A: OSIRIS/GTC observations DATE: 21/07/29 12:54:52 GMT FROM: Alexander Kann at IAA-CSIC D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all HETH/IAA-CSIC), J. P. U. Fynbo (DAWN/NBI), L. Izzo (DARK/NBI), N. R. Tanvir (U. Leicester), and G. Gomez Velarde (GRANTECAN) report: We observed the XRT afterglow position (Osborne et al., GCN #30524) of GRB 210726A (Bernardini et al., GCN #30523), classified as a short GRB (Tohuvavohu, GCN #30535; Palmer et al., GCN #30536; Veres, GCN #30540) with OSIRIS mounted on the 10.4m Gran Telescopio Canarias (Observatorio Astrofíisco Roque de Los Muchachos, La Palma, Canary Islands, Spain), under mediocre conditions and at high airmass, starting July 26, 21:21:31 UT, 2.041 h after the GRB. We obtained a sequence of 30, 30, 60, 30 s images in r' for a total integration time of 150 s. Within the XRT error circle, we do not detect any source down to r' > 24.4 mag (AB magnitude), measured against a nearby PanSTARRS fiel star, at 0.088533 d (2.125 h) after the burst, in agreement with Kann et al., GCN #30543. The possible host galaxy (Watson et al., GCN #30534, Kann et al., GCN #30543) is found at r' = 22.04 +/- 0.05 mag, again in agreement with detections from the PanSTARRS and SDSS surveys.
GCN 30558 table
GRB_name GRB210726A
GCN_number 30558
Detection_method Swift-XRT Other
ra 193.2904°
decl 19.1902°
Circular_text TITLE: GCN CIRCULAR NUMBER: 30558 SUBJECT: GRB 210726A: Chandra detection of the X-ray afterglow DATE: 21/07/30 23:26:02 GMT FROM: Alicia Rouco Escorial at CIERA A. Rouco Escorial, W. Fong, K. Paterson (Northwestern University), R. Margutti (UC Berkeley) and E. Berger (Harvard University) report: “We initiated observations with the Chandra X-ray Observatory of the short-duration GRB 210726A (Bernardini et al., GCN 30523; Tohuvavohu, GCN 30535; Palmer, GCN 30536) starting on 2021 July 29 16:04:38 UT, with a median observation time of ~3 days post-trigger. We obtained one ACIS-S observation under the Proposal 22400461 (ObsID 23445; PI: Fong), with an effective exposure time of ~24.6 ks. We obtain a ~7sigma detection of GRB 210726A with a total net source counts of 76+/-10 (0.5-7 keV). The Chandra position of the short GRB is fully consistent with the enhanced Swift-XRT position (90% confidence; XRT GRB catalogue, Evans et al., 2009). The Chandra position is: RA(J2000)= 12h53m09.7s Dec(J2000)=19d11m24.6s with a total positional uncertainty of 0.81 arcsec (largely dominated by Chandra's absolute astrometric uncertainty). Based on our MCMC modeling, the XRT and Chandra afterglow flux, starting at ~120.89 s post-burst, can be modeled with a broken power-law decline characterized by a second segment with a decay index (F~t^alpha) of alpha2=-0.62 (-0.05,+0.04) starting at ~418 s post-burst. In particular, the Chandra detection roughly follows the latest decline rate based on XRT data alone.. Further Chandra observations are planned. We thank the Chandra Director, Pat Slane, and staff for the rapid planning and scheduling of these observations.”
GCN 30658 table
GRB_name GRB210726A
GCN_number 30658
Detection_method VLA Det
ra 193.2908°
decl 19.1903°
Circular_text TITLE: GCN CIRCULAR NUMBER: 30658 SUBJECT: GRB 210726A: VLA radio afterglow detection DATE: 21/08/18 20:48:40 GMT FROM: Genevieve Schroeder at Northwestern University G. Schroeder, K. D. Alexander, W. Fong, A. Rouco Escorial, (Northwestern), T. Laskar (U. of Bath), E. Berger (Harvard) report: "We re-observed the position of short GRB 210726A (Bernardini et al., GCN 30523; Veres et al., GCN 30540; Palmer et al., GCN 30536; Tohuvavohu et al., GCN 30535) with the Karl G. Jansky Very Large Array (VLA) under program 20B-057 (PI: Fong) beginning on 2021 August 07.02 UT (11.21 days post-burst) at a mean frequency of 6 GHz. In 1.5 hour of observations we detect a radio source with a preliminary flux density of ~40 uJy. The position of this radio source is fully consistent with the position of the X-ray afterglow (Osborne et al., GCN 30524; Rouco Escorial et al., GCN 30558) at: RA(J2000): 12:53:09.8 Dec(J2000): +19:11:25.1 with an uncertainty of 0.6 arcsec in each coordinate. We obtained further VLA observations at 6 GHz and 10 GHz beginning on 2021 August 14.75 UT (18.94 days post-burst) and detect the source at both frequencies. We find a significant brightening at 6 GHz, confirming this source as the radio afterglow of GRB210726A. We note that this radio afterglow is among the brightest ever detected for a short GRB to date. Further observations are planned. We thank the VLA staff for quickly approving and executing these observations."