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This page lists all entries on GRB250605A in GRBweb

Summary Swift GCN 40633 GCN 40634 GCN 40642 GCN 40644 GCN 40645 GCN 40657 GCN 40667

Summary table
Variable	Value	Source
T0	18:52:31.270 UTC	GCN_circulars,Swift Det
ra	166.9571°	Swift
decl	-19.7882°	Swift
pos_error	7.12e-04°	Swift
GBM_located	False
mjd	60831.78647303241	GCN_circulars,Swift Det

Swift table
GRB_name	GRB250605A
t_trigger	18:52:31.270 UTC
ra	166.9571°
decl	-19.7882°
pos_error	7.12e-04°

GCN 40633 table
GRB_name	GRB250605A
GCN_number	40633
Detection_method	Swift Det
t_trigger	18:52:31.270 UTC
ra	166.9770°
decl	-19.7950°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40633 SUBJECT: GRB 250605A: Swift detection of a burst DATE: 25/06/05 19:08:03 GMT FROM: K.L. Page at U Leicester R. Gupta (NASA GSFC), J. J. DeLaunay (PSU), S. Dichiara (PSU), C. Gronwall (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), H. A. Krimm (NSF), M. J. Moss (GSFC), K. L. Page (U Leicester), T. M. Parsotan (GSFC), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 18:52:31.27 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250605A (trigger=1321323). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 166.977, -19.795 which is RA(J2000) = 11h 07m 54s Dec(J2000) = -19d 47' 42" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a complex light curve with one strong pulse between T0-2 sec to T0+10 sec and a second dimmer but broad pulse between T0+40 sec to T0+100 sec. The peak count rate was 4,000 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 18:54:09.2 UT, 98.0 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 166.9571, -19.7882 which is equivalent to: RA(J2000) = 11h 07m 49.70s Dec(J2000) = -19d 47' 17.5" with an uncertainty of 5.5 arcseconds (radius, 90% containment). This location is 71 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. UVOT took a finding chart exposure of 144 seconds with the White filter starting 106 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.039. Burst Advocate for this burst is R. Gupta (rahulbhu.c157 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/)

GCN 40634 table
GRB_name	GRB250605A
GCN_number	40634
Detection_method	Optical
ra	166.9571°
decl	-19.7876°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40634 SUBJECT: GRB 250605A: LT optical observations DATE: 25/06/05 22:51:33 GMT FROM: Ben Gompertz at U of Birmingham B. P. Gompertz (U. Birmingham), Dimple (U. Birmingham), A. Martin-Carrillo (UCD), G. Corcoran (UCD) and D. B. Malesani (DAWN/NBI and Radboud), report on behalf of a larger collaboration: We initiated follow-up observations of GRB 250605A (Gupta et al., GCN 40633) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 20:48:52.89 UT, ~2 hours after the Swift/BAT trigger, and consisted of 10x60 s exposures in the SDSS i filter. Observations were taken close to twilight, at high airmass, and the target was 28 deg from the moon at 77% illumination. Within the Swift/XRT error box, we detect a possible optical counterpart, not present in archival imaging, with an AB magnitude of i ~ 21.1 at RA = 11:07:49.7, Dec = -19:47:15.4. However, this detection is only significant at the 2-sigma level and further, deeper observations are required to confirm its reality. Formally, we measure a 3-sigma upper limit of i > 20.6 within the XRT localisation region. We also note the presence of a faint source visible in the Legacy Survey archival imaging with an AB magnitude of i = 23.54. The source position is consistent with the possible optical counterpart, and may be the host galaxy of GRB 250605A. Magnitudes are calibrated against nearby Pan-STARRS stars and not corrected for galactic extinction.

GCN 40642 table
GRB_name	GRB250605A
GCN_number	40642
Detection_method	Swift-XRT Det
ra	166.9572°
decl	-19.7884°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40642 SUBJECT: GRB 250605A: Enhanced Swift-XRT position DATE: 25/06/06 08:44:00 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 3740 s of XRT Photon Counting mode data and 7 UVOT images for GRB 250605A, 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 = 166.95715, -19.78841 which is equivalent to: RA (J2000): 11h 07m 49.72s Dec (J2000): -19d 47' 18.3" with an uncertainty of 2.0 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 40644 table
GRB_name	GRB250605A
GCN_number	40644
Detection_method	Swift-XRT Other
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40644 SUBJECT: GRB 250605A: Swift-XRT refined Analysis DATE: 25/06/06 11:02:50 GMT FROM: Phil Evans at U of Leicester A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), M.A. Williams (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.0 ks of XRT data for GRB 250605A, from 90 s to 50.2 ks after the trigger. The data comprise 149 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=4.36 (+0.19, -0.15). At T+164 s the decay flattens to an alpha of 3.19 (+0.29, -0.32) before breaking again at T+326 s to a final decay with index alpha=0.79 (+/-0.07). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.12 (+0.06, -0.05). The best-fitting absorption column is 2.59 (+0.20, -0.19) x 10^21 cm^-2, in excess of the Galactic value of 4.3 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.10 (+0.13, -0.12) and a best-fitting absorption column of 2.9 (+/-0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (5.5 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.9 (+/-0.5) x 10^21 cm^-2 Galactic foreground: 4.3 x 10^20 cm^-2 Excess significance: 8.7 sigma Photon index: 2.10 (+0.13, -0.12) If the light curve continues to decay with a power-law decay index of 0.79, the count rate at T+24 hours will be 0.085 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.0 x 10^-12 (4.7 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/01321323. This circular is an official product of the Swift-XRT team.

GCN 40645 table
GRB_name	GRB250605A
GCN_number	40645
Detection_method	Optical
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40645 SUBJECT: GRB 250605A: SVOM/VT optical upper limit DATE: 25/06/06 15:40:20 GMT FROM: Huali Li at at NAOC, SVOM L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Z. H. Yao, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT conducted ToO follow-up observations of the GRB 250605A (Gupta et al., GCN 40633, Melandri et al., GCN 40644). The observation started on 2025-06-06T05:02:39 UT in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No uncatalogued sources are detected in single or stacked images within the Swift/XRT error box (Evans et al., GCN 40642) and the possible optical candidate reported by Gompertz et al. (GCN 40634). The 3 sigma limit magnitudes are derived as below: Mid time | Band | Exposure Time | 3 sigma limit magnitude 11.28 hour VT_B 59*70 sec >23.6 mag 11.28 hour VT_R 59*70 sec >23.6 mag The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.

GCN 40657 table
GRB_name	GRB250605A
GCN_number	40657
Detection_method	Swift-UVOT Other
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40657 SUBJECT: GRB 250605A: Swift/UVOT Upper Limits DATE: 25/06/09 17:13:08 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and R. Gupta (NASA GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250605A 107 s after the BAT trigger (Gupta et al., GCN Circ. 40633). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 40642) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 107 251 141 >20.9 white 5225 11166 933 >21.41 v 16403 17310 885 >20.07 b 5020 5220 196 >19.83 u 4815 22332 204 >19.32 uvw1 21418 22318 885 >20.16 uvm2 17315 18088 761 >20.44 uvw2 11173 11858 674 >20.47 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.039 in the direction of the burst (Schlegel et al. 1998).

GCN 40667 table
GRB_name	GRB250605A
GCN_number	40667
Detection_method	Swift-BAT Det
ra	166.9630°
decl	-19.7860°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40667 SUBJECT: GRB 250605A: Swift-BAT refined analysis DATE: 25/06/10 13:23:05 GMT FROM: Mike Moss at NASA GSFC R. Gupta (GSFC), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (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 250605A (trigger #1321323) (Gupta, et al., GCN Circ. 40633). The BAT ground-calculated position is RA, Dec = 166.963, -19.786 deg which is RA(J2000) = 11h 07m 51.1s Dec(J2000) = -19d 47' 10.5" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 35%. The BAT light curve shows a complex light curve with multiple emission episodes: a period of very dim extended emission between ~T0-100 sec to T0-10 leading up to one strong pulse between T0-10 sec to T0+10 sec and followed by a dim broad pulse between T0+40 sec to ~T0+125 sec. T90 (15-350 keV) is 176.05 +- 5.15 sec (estimated error including systematics). The time-averaged spectrum from T-100.30 to T+126.69 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.50 +- 0.22, and Epeak of 76.7 +- 27.6 keV (chi squared 71.54 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.0 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T-0.00 sec in the 15-150 keV band is 6.1 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.83 +- 0.05 (chi squared 79.05 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1321323