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This page lists all entries on GRB250706B in GRBweb

Summary IPN Swift GCN 40989 GCN 40991 GCN 40992 GCN 40995 GCN 40996 GCN 41007 GCN 41009 GCN 41015 GCN 41022 GCN 41026

Summary table
Variable	Value	Source
T0	17:06:04 UTC	Swift
ra	41.2302°	Swift
decl	-50.0609°	Swift
pos_error	4.53e-04°	Swift
redshift	0.9420
GBM_located	False
mjd	60862.712546296294	Swift

IPN table
GRB_name	GRB250706B
ra	41.1333°
decl	-50.1167°
pos_error	1.33e-01°
redshift	0.9420

Swift table
GRB_name	GRB250706B
t_trigger	17:06:04 UTC
ra	41.2302°
decl	-50.0609°
pos_error	4.53e-04°

GCN 40989 table
GRB_name	GRB250706B
GCN_number	40989
Detection_method	Other
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40989 SUBJECT: GRB 250706B: SVOM detection of a long burst DATE: 25/07/06 17:33:22 GMT FROM: SVOM_group Jesse Palmerio, Dylan Adrien, Nicolas Dagoneau (CEA), Marius Brunet (IRAP), Maria Grazia Bernardini (INAF-OAB, LUPM), Charlotte Van Hove (IJCLab), Pierre Maggi (ObAS) report on behalf of the SVOM mission team: At 2025-07-06T17:06:04 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250706B (SVOM burst-id sb25070609). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Image Trigger (IMT), which produced a sequence of 7 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 10.09 in the [5-20] keV energy band over a time window of 81.92 seconds starting at 2025-07-06T17:05:23. The localization of the best alert is R.A., Dec. 41.1337, -50.1172 degrees (J2000) with a 90% confidence level (C.L.) radius of 7.89 arcmin (including systematic error of 2 arcmin added in quadrature). SVOM slewed to the burst. SVOM/MXT began observing the field at 2025-07-06T17:08:42 UTC, 158 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 41.2300, -50.0621 degrees: R.A. (J2000) = 2h44m55.20s Dec. (J2000) = -50d03m43.51s with a 90% C.L. radius of 38 arcseconds. This location is 4.97 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Jesse Palmerio: palmerio@cea.fr. Please contact the BA by email if you require additional information.

GCN 40991 table
GRB_name	GRB250706B
GCN_number	40991
Detection_method	Optical
ra	41.2310°
decl	-50.0612°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40991 SUBJECT: GRB 250706B: TRT bright optical counterpart detection DATE: 25/07/06 18:32:19 GMT FROM: Dong Xu at NAOC/CAS Z.P. Zhu (NAOC), K. Noysena, S. Tinyanont, K. Chanchaiworawit (NARIT), S.Q. Jiang, X. Liu, J. An, L.B. He, D. Xu (NAOC), S.Y. Fu (HUST) report on behalf of a large collaboration: We observed the field of GRB 250706B detected by SVOM/ECLAIRs (Palmerio et al., GCN 40989) using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at New South Wales, Australia (SBO). Observations started at 17:41:58 UTC on 2025-07-06, i.e., 35.9 min after the SVOM trigger and a series of frames in the R band were obtained. An uncatalogued and varying optical transient is detected within the SVOM/MXT error circle (Palmerio et al., GCN 40989) at coordinates R.A. (J2000) = 02:44:55.45 Dec. (J2000) = -50:03:40.32 with an uncertainty of ~0.5 arcsec. It has R ~ 15.5 mag in the first R-band frame, calibrated with Legacy Survey DR-10 and not corrected for Galactic extinction. We thus think this is the optical afterglow of the GRB.

GCN 40992 table
GRB_name	GRB250706B
GCN_number	40992
Detection_method	Optical
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40992 SUBJECT: GRB 250706B: SVOM/VT optical observation DATE: 25/07/06 18:45:55 GMT FROM: SVOM_group After the trigger by SVOM/ECLAIRs at 2025-07-06T17:06:04 UTC (T0), SVOM performed an automatic slew on the burst location (Palmerio et al., GCN 40989). SVOM/VT began observing the field at 2025-07-06T17:10:48, 283.83 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the 1-bit subimage and source list downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 50: This candidate was flagged as un uncatalogued source whose magnitude varied with 3 sigma significance. The position of this candidate is R.A., Dec. 41.2311, -50.0612 degrees, corresponding to: R.A. (J2000) = 2h44m55.5s Dec. (J2000) = -50d03m40.4s with an uncertainty of 1 arcsec. This location is within the R90 uncertainty region of the SVOM/MXT onboard localization. This location is consistent with the optical afterglow reported by Zhu et al. (GCN 40991). The source was detected in both VT_R and VT_B, and was fading between the first 2 VT observing sequences. The candidate's magnitudes are: | date-obs (UTC) | mid-time | exposure | band | mag(AB) | | -------------------- | ----------- | --------- | ----- | ------------- | | 2025-07-06T17:10:48 | 7.23 min | 6*50 sec | VT_B | 14.90 ± 0.01 | | 2025-07-06T17:10:48 | 7.23 min | 6*50 sec | VT_R | 14.48 ± 0.01 | | 2025-07-06T17:15:48 | 12.23 min | 6*50 sec | VT_B | 15.17 ± 0.01 | | 2025-07-06T17:15:48 | 12.23 min | 6*50 sec | VT_R | 14.65 ± 0.01 | Magnitudes were not corrected for dust extinction. Given the VT colour of the counterpart, it might be a low redshift gamma-ray burst. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. The SVOM/VT point of contact for this burst is Jesse Palmerio: palmerio@cea.fr.

GCN 40995 table
GRB_name	GRB250706B
GCN_number	40995
Detection_method	Optical
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40995 SUBJECT: GRB 250706B: iTelescope optical observations DATE: 25/07/06 20:59:09 GMT FROM: Filipp Dmitrievich Romanov at Amateur astronomer On 2025-07-06 I observed the field of GRB 250706B (Palmerio et al., GCN Circ. 40989) remotely using the telescopes T33 (0.3-m f/9 reflector + CCD with Astrodon Series II Red filter) and T17 (0.43-m f/6.8 reflector + CMOS with Astrodon Red-E filter) of iTelescope.Net at Siding Spring Observatory, Australia. The exposure times of the photographs were 300 seconds, observations started at 19:56:23 UT (2h 50m after the trigger). I detected the optical afterglow in all images with the position (J2000): 02:44:55.46 -50:03:40.1. I measured the magnitudes (compared to r' magnitudes of nearby stars from the APASS DR9 catalog: Henden et al., 2016): Mid-time (UT) | Magnitude | Error | Telescope | 19:58:53.3 16.852 0.073 T33 20:04:55.9 16.790 0.046 T33 20:10:58.5 16.756 0.110 T33 20:17:00.3 16.752 0.071 T33 20:05:50.8 16.738 0.040 T17 20:11:47.9 16.875 0.054 T17 20:17:43.6 16.833 0.076 T17 Magnitudes were not corrected for Galactic extinction. F. D. Romanov (AAVSO).

GCN 40996 table
GRB_name	GRB250706B
GCN_number	40996
Detection_method	Swift-XRT Other
ra	41.2296°
decl	-50.0604°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 40996 SUBJECT: GRB250706B: Swift-XRT counterpart detection DATE: 25/07/06 21:33:59 GMT FROM: Phil Evans at U of Leicester M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M.A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. D'Ai (INAF-IASFPA) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift has performed follow-up observations of the SVOM detected burst GRB250706B (GCN 40989), collecting 1.6 ks of XRT data from 1.4 ks to 3.0 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. A candidate X-ray counterpart has been found with a position RA, Dec = 41.2296, -50.0604 which is equivalent to: RA (J2000): 02 44 55.11 Dec(J2000): -50 03 37.5 with an uncertainty of 3.5 arcsec (radius, 90% confidence). We consider the X-ray source the afterglow of GRB 250706B, even if this position appears only marginally consistent with the optical counterpart detected by TRT (Zhu et al., GCN 40991) and from SVOM/VT (GCN 40992). The light curve can be modelled with an initial power-law decay with an index of alpha=0.93 (+0.17, -0.21), followed by a break at T+2679 s to an alpha of 8.0 (+0.0, -1.4). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.50 (+/-0.07). The best-fitting absorption column is 1.11 (+0.24, -0.23) x 10^21 cm^-2, in excess of the Galactic value of 2.8 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.3 x 10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.11 (+0.24, -0.23) x 10^21 cm^-2 Galactic foreground: 2.8 x 10^20 cm^-2 Excess significance: 5.9 sigma Photon index: 1.50 (+/-0.07) If the light curve continues to decay with a power-law decay index of 8.0, the count rate at T+24 hours will be 1.3 x 10^-11 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.6 x 10^-22 (6.2 x 10^-22) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019912. This circular is an official product of the Swift-XRT team.

GCN 41007 table
GRB_name	GRB250706B
GCN_number	41007
Detection_method	Optical
Circular_text	TITLE: GCN CIRCULAR NUMBER: 41007 SUBJECT: GRB 250706B: REM optical observations DATE: 25/07/07 10:23:35 GMT FROM: Riccardo Brivio at INAF-OAB R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of GRB 250706B detected by SVOM/ECLAIRs (Palmerio et al., GCN 40989) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, and z bands, started on 2025 July 07 at 05:14:01 UT (i.e. 12.1 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not detect any counterpart at the position of the optical afterglow (Zhu et al., GCN 40991; Romanov, GCN 40995) down to the following 3sigma limit: r > 19.2 (AB; calibrated against the SkyMapper catalogue), at a mid-time of 13.0 hr after the trigger.

GCN 41009 table
GRB_name	GRB250706B
GCN_number	41009
Detection_method	Optical
ra	41.2390°
decl	-50.0650°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 41009 SUBJECT: GRB 250706B: refined SVOM/MXT data analysis DATE: 25/07/07 15:24:57 GMT FROM: SVOM_group P. Maggi (ObAS), D. Götz (CEA), H. Goto (Kanazawa University/CEA), M. Moita (CEA), C. Plasse (CEA), F. Robinet (IJCLab), C. Van Hove (IJCLab) report of behalf of the SVOM/MXT Team: GRB 250706B (Palmerio et al. GCN 40989) was observed by SVOM/MXT after an automatic SVOM slew, starting at T0 = 2025-07-06T17:08:42.6 (158 s after trigger time Tb). MXT observed during 6 orbits for 13.6 ks effective exposure time. Using the full X-band dataset, the X-ray source afterglow is located at R.A., Dec = 41.239, -50.065 degrees: R.A. (J2000) = 02h44m57.45s Dec. (J2000) = -50d03m55.6s with a 90% C.L. radius of 31 arcseconds (including 30 arcseconds systematic error added in quadrature) and consistent with the reported optical VT position (Palmerio et al. GCN 40992). The spectrum is modelled with an absorbed power law. Across the full data set the absorption column NH is consistent within uncertainties, between 2 and 3 x 1e22 /cm2 (all uncertainties are at the 90% C.L.). The photon index evolves from 2.25 (-0.16/+0.18) within 1200s of trigger time, to 2.53 (-0.25/+0.28) at Tb + 5 ks < t < Tb+ 20 ks, and softens further to 3.43 (-1.04/+1.45) at t > Tb + 25 ks. The 0.3-10 keV flux is 8.24e-10 (-0.91/+0.82) x 1e-10 erg/cm2/s, 8.9 (-1.0/+1.2) x 1e-11 erg/cm2/s, and down to <1.0 x 1e-11 erg/cm2/s during the same intervals. We observe a complex light curve with at least 3 power-law segments with count rate proportional to t^alpha, with: alpha = -0.42 +/-0.02 until Tb+5031s +/-277s alpha = -1.57 +/-0.07 until Tb+24326s +/-3479s alpha = -3.05 +/-1.62 afterwards The SVOM/MXT light curve can be found here: https://seafile.unistra.fr/f/909c01d644774417897e/. With the spectrum reported in the first interval, a count rate of 1 count/s corresponds to a flux of 1.89x1e-10 erg/cm2/s. Follow-up observations at other wavelengths are encouraged. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE. The SVOM point of contact for this burst is Jesse Palmerio: palmerio@cea.fr Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.

GCN 41015 table
GRB_name	GRB250706B
GCN_number	41015
Detection_method	Swift-UVOT Det
ra	41.2226°
decl	-50.0612°
Circular_text	TITLE: GCN CIRCULAR NUMBER: 41015 SUBJECT: GRB 250706B: Swift/UVOT Detection DATE: 25/07/07 18:35:19 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250706B 12.5 ks after the SVOM/ECLAIRs trigger (Palmerio et al., GCN Circ. 40989). A source consistent with the XRT position (Ferro et al., GCN Circ. 40996) and the optical transient (Zhu et al., GCN Circ. 40991; Palmerio et al., GCN Circ. 40992; Romanov, GCN Circ. 40995) is detected in the UVOT exposures. The preliminary UVOT position is: RA (J2000) = 02:44:53.43 = 41.23097 (deg.) Dec (J2000) = -50:03:40.2 = -50.06116 (deg.) with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag u 12471 18805 2023 16.49+/-0.03 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.026 in the direction of the burst (Schlegel et al. 1998).

GCN 41022 table
GRB_name	GRB250706B
GCN_number	41022
Detection_method	Optical
redshift	0.9420
Circular_text	TITLE: GCN CIRCULAR NUMBER: 41022 SUBJECT: GRB 250706B/C: VLT/X-shooter redshift z = 0.942 DATE: 25/07/08 12:04:56 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute J. T. Palmerio (CEA/Irfu), B. Schneider (LAM), A. Saccardi (CEA/Irfu), M. Garnichey (LUX-Paris Obs.), G. Corcoran (UCD), V. D'Elia (ASI/SSDC), M. De Pasquale (Univ. Messina), L. Izzo (INAF/OACn and DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud), P. O'Brien (Leicester), N. R. Tanvir (Univ. Leicester), S. D. Vergani (LUX-Paris Obs.) report on behalf of the Stargate collaboration: We observed the optical afterglow (Zhu et al., GCN 40991) of the SVOM GRB 250706B (Palmerio et al., GCN 40989), an extension of GRB 250706C detected by Konus-Wind and Fermi/LAT (Frederiks et al., GCN 41013; Longo et al., GCN 41019), using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-25000 AA, and consist of 2 exposures of 600 s each. The observation mid time was 2025 Jul 8.40 UT (1.70 days after the Konus-Wind trigger). In a 30 s image taken with the acquisition camera on Jul 8.39 UT (1.69 days after the Konus-Wind trigger), the optical afterglow is clearly detected, and we measure a magnitude r = 20.37 +- 0.02 AB (calibrated against a single star from the SkyMapper catalog). In a preliminary reduction of the spectra, continuum is visible over the entire covered wavelength range. From the detection a multitude of absorption lines, which we interpret as due to Al II, Ni II, Si II, Si II*, Al III, Cr II, Zn II, Ni II*, Fe II, Fe I, Mn II, Mg II, Mg I, Ca II, Ca I, we infer a redshift of z = 0.942. We also detect two emission lines which we identify as the [O III] 4959,5007 doublet at the same redshift. The detection of fine-structure lines, as well as of nebular emission, allows us to securely identify z = 0.942 as the redshift of GRB 250706B/C. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Diego Parraguez. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495).

GCN 41026 table
GRB_name	GRB250706B
GCN_number	41026
Detection_method	Optical
Circular_text	TITLE: GCN CIRCULAR NUMBER: 41026 SUBJECT: GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C DATE: 25/07/08 13:38:21 GMT FROM: SVOM_group J. T. Palmerio, D. Adrien (CEA), M. G. Bernardini (INAF-OAB, LUPM), M. Brunet, J.-L. Atteia, O. Godet (IRAP), P. Maggi (ObAS), L. P. Xin (NAOC), D. B. Malesani (DAWN/NBI and Radboud), C. W. Wang (IHEP), A. Saccardi, D. Götz (CEA), F. Cangemi (APC) report on behalf of the SVOM mission team: Following the detection of GRB 250706C reported by Konus-Wind (Frederiks et al., GCN 41013) and Fermi/LAT (Longo et al., GCN 41019), we discuss below the interpretation of GRB 250706B detected by SVOM (Palmerio et al., GCN 4989) as the hard X-ray afterglow of GRB 250706C. At the Konus-Wind trigger time (Frederiks et al., GCN 41013), the position of GRB 250706B was occulted by the Earth for SVOM/ECLAIRs. The SVOM/ECLAIRs trigger for GRB 250706B occurred 21 min after the Konus-Wind trigger, right after the source was no longer occulted by the Earth. SVOM/ECLAIRs shows a featureless and long-lasting (~1000 s) emission in the 4-50 keV energy band. The time-averaged spectrum after the slew (from 134 s to 1000 s after the ECLAIRs trigger time, GCN 4989) in the energy range 5-120 keV is best fitted by a power law model with index 2.01 +/- 0.11 (68% c.l. errors). With this model, the total 4-120 keV fluence is 2.6e-6 erg/cm^2. There is no significant signal in the SVOM/GRM VHF data. Taking the Konus-Wind detection time as T0 (16:45:22 UT), the SVOM/VT lightcurve appears as a single, unbroken power-law with index ~1.2. Assuming the same power-law decay held continuously before the VT observations, extrapolating the optical light curve to T0 + 1 min yields a magnitude of roughly 10 in VT_R. We encourage all-sky monitors to check for any emission at this location around the Konus-Wind trigger time. Extrapolating the SVOM/MXT lightcurve to T0 + 1 min yields a 0.3-10 keV flux of 6.5x10^-8 erg/cm^2/s, assuming the same power-law decay held continuously before the MXT observations reported by Maggi et al. (GCN 41009). We encourage further follow-up of this burst. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The SVOM point of contact for this burst is Jesse Palmerio: palmerio@cea.fr Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.