GRB 261007A, EP261007a
GCN Circular 45869
Subject
GRB 261007A / EP261007a: SVOM/GWAC-F60A/B observations
Date
2026-10-09T00:16:20Z (4 hours ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
S.J. Yin (GXU), C. Wu, L.P. Xin, X.H. Han, P.P. Zhang, J.L. Wang (NAOC), report on behalf of the SVOM follow-up team:
We observed the field of GRB261007A detected by SVOM/ (Goto et al., GCN 45824), with the GWAC-F60 at Xinglong Observatory, China. F60 started observing at 2026-10-07T14:00:22.98 UTC in R-band.
The optical counterpart (Zheng et al., GCN 45825; Saccardi et al., GCN 45829; Mohan et al., GCN 45832; Saccardi et al., GCN 45837; Shi et al., GCN 45838) is faintly detected in our images. We measure the following magnitudes calibrated against the USNO-B1.0 catalog, and not corrected for Galactic extinction: from forced photometry of the faint source,
R = 20.15 +/- 0.3 mag (mid-time 8.8 hr after the trigger);
Two 60cm GWAC-F60(A/B) are operated by Guangxi University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 19*19 arcmin.
GCN Circular 45867
Subject
GRB 261007A: Glowbug gamma-ray detection
Date
2026-10-08T18:30:47Z (10 hours ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 261007A, which was also detected by SVOM (GCN 45824, 45863), Einstein Probe (GCN 45828), Fermi/GBM (GCN 45830), NuSTAR (GCN 45846), and AstroSat CZTI (GCN 45859).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-10-07 05:39:48.536 with a duration of 26.6 s and a total significance of about 77 sigma. The light curve comprises a bright multi-peaked structure.
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular 45865
Subject
GRB 261007A: NOT optical observations
Date
2026-10-08T16:07:48Z (12 hours ago)
From
d.s.oneill@bham.ac.uk
Via
Web form
D. O’Neill (Birmingham), D. B. Malesani (DAWN/NBI), A. S. Mårtensson (NOT), A. Caballero Almagro (NOT), report on behalf of a larger collaboration:
We observed the optical counterpart (Zheng et al., GCN 45825; Saccardi et al., GCN 45829; Mohan et al., GCN 45832; Saccardi et al., GCNs 45837, 45837; Shi et al., GCN 45838; An et al., GCN 45840; Arya et al., GCN 45841; Rehemtulla et al., GCN 45843; Ruiz-Laguna et al., GCN 45844; Angulo et al., GCN 45848; Li et al., GCN 45851; Chen et al., GCN 45855; Zhang et al., GCN 45856) of GRB 261007a/EP261007a (Fermi GBM team, GCN Circ. 45830; SVOM/ECLAIRs: Goto et. al., GCN Circ. 45824; SVOM/GRB: Ren et al., GCN 45863; Einstein Probe: Wen et. al., GCN Circ. 45828; NuSTAR: Waratkar et. al., GCN Circ. 45846; AstroSat CZTI: Harsha et. al., GCN 45859) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument. Observations were performed starting at 01:38:38 UT on October 8 2026 (about 20 hr after SVOM trigger), and consisted of 3x300 s in the SDSS-r band.
In our stacked images we measure an AB magnitude:
r = 21.36 ± 0.04
This magnitude is calibrated using nearby objects from the Pan-STARRS catalog and is not corrected for Galactic extinction.
GCN Circular 45863
Subject
GRB 261007A: SVOM/GRM observation
Date
2026-10-08T15:46:35Z (12 hours ago)
From
renyz16607@163.com
Via
Web form
SVOM/GRM team: Yang-Zhao Ren, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Olivier Godet (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by GRB 261007A (SVOM trigger reference: sb26100701) at 2026-10-07T05:39:49.800 UTC (T0), which is also detected by SVOM/ECLAIRs (Hatsune Goto et. al., GCN #45824), EP (Wen et. al., GCN #45828), Fermi/GBM (Fermi GBM team, GCN #45830), NuSTAR (Waratkar et. al., GCN #45846) and AstroSat/CZTI (Harsha et. al., GCN #45859).
With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 25.0 +0.5/-0.5 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn/gcn/2026/svgrb261007A.png
In addition, the position of this burst, as determined by SVOM/ECLAIRs (RA= 11.5787 deg, Dec=-17.6698 deg, ERR= 9.61 arcmin, GCN #45824), is located at about 28 degrees from the SVOM optical axis.
With this localization, the time-averaged spectrum from T0 to T0+30 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.66 +0.02/-0.02 and the cutoff energy, parameterized as Epeak, is 316 +8/-7 keV. The event fluence (10-1000 keV) in this time interval is (8.54 +0.13/-0.12)E-05 erg/cm^2.
The 1s peak spectrum, measured from T0+21.7 to T0+22.7 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.59 +0.03/-0.03 and the cutoff energy, parameterized as Epeak, is 322 +14/-13 keV. The flux (10-1000 keV) in this time interval is (2.85 +0.05/-0.04)E-06 erg/cm^2/s.
The localization of GRB 261007A in the 'Amati' relation diagram is shown at:
https://www.bursthub.cn/gcn/2026/svgrb261007A_amati.png
The localization of GRB 261007A in the 'Yonetoku' relation diagram is shown at:
https://www.bursthub.cn/gcn/2026/svgrb261007A_yonetoku.png
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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Yang-Zhao Ren (IHEP)(renyz@ihep.ac.cn)
GCN Circular 45859
Subject
GRB 261007A / EP261007a: AstroSat CZTI detection
Date
2026-10-08T13:11:37Z (15 hours ago)
Edited On
2026-10-08T14:35:18Z (14 hours ago)
From
ABHINAV GOYAL at Indian Institute of Technology Bombay <abhigoyale2003@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of ABHINAV GOYAL at Indian Institute of Technology Bombay <abhigoyale2003@gmail.com>
Via
Web form
Harsha K. H. (IUCAA), S. Salunke (IUCAA), S. Puri (IITB), A. Goyal (IITB), A. Arya (IITB), G. Waratkar (Caltech/IITB), V. Bhalerao (IITB), A. Vibhute (IUCAA), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a GRB 261007A which was also detected by Fermi (Fermi GBM team, GCN Circ. 45830), SVOM/ECLAIRs (Goto et. al., GCN Circ. 45824), associated with EP261007a detected by Einstein Probe (Wen et. al., GCN Circ. 45828), and NuSTAR (Waratkar et. al., GCN Circ. 45846).
The source was detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-10-07 05:40:02.36 UTC. The measured peak count rate associated with the burst is 1427 (+79, -36) counts/s above the background in the combined data of all quadrants, with a total of 15823 (+333, -396) counts. The local mean background count rate was 307 (+3, -3) counts/s. We measure a T90 of 22.9 (+0.3, -0.4) s from the cumulative CZT light curve.
The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-10-07 05:40:11.67 UTC. The measured peak count rate associated with the burst is 2125 (+88, -77) counts/s above the background in the combined data of all quadrants, with a total of 21607 (+536, -496) counts. The local mean background count rate was 772 (+6, -5) counts/s. We measure a T90 of 22.4 (+0.3, -0.3) s from the cumulative Veto light curve.
In the preliminary analysis, we find 1822 Compton events associated with this event.
CZTI data products like interactive and downloadable light curves for this GRB can be found at:
https://astrosat.iucaa.in/cift/cift_products/ET20261007T053949/ET20261007T053949_details.html
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 45856
Subject
EP261007a/GRB 261007A：Xinglong optical observation
Date
2026-10-08T11:02:58Z (17 hours ago)
From
Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>
Via
Web form
Junbo-Zhang (NAOC), Junjie-Jin (NAOC), Rui-Zhu (NAOC), Haiyang-Mu (NAOC), Feng-Xiao (NAOC), Yuguang-Sun (NAOC), Jie-Zheng (NAOC), Dong-Xu (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration
Following the detection of GRB 261007A by SVOM (Goto et al., GCN 45824) and EP261007a by EP-WXT (Wen et al., GCN 45828), we observed the field of EP261007a/GRB 261007A using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 6x300s clear-band frames with a median time of 2026-10-07 15:09:20 (UT) (8.37 h after the EP trigger and 9.45 h after the SVOM trigger).
The stacked clear-band image using the 2.16-m telescope has a 5-sigma limiting magnitude of ~21.33 mag, calibrated with the Pan-STARRS field. And the optical afterglow was detected in our stacked frame with a magnitude of 20.044 +- 0.071 mag.
GCN Circular 45855
Subject
GRB 261007A/EP261007a: Optical follow-up observations with Kinder
Date
2026-10-08T09:52:27Z (18 hours ago)
From
Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>
Via
Web form
Z.-Y. Chen, A. Aryan, T.-W. Chen, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), S. J. Smartt, J. H. Gillanders (both Oxford), S. Yang (HNAS), A. Sankar.K, K. N.-T. Ho, A. Dutta, M.-H. Lee, Y.-H. Lee, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, H.-C. Lin, H.-Y. Hsiao, W.-J. Hou, J.-K. Guo (all NCU), Z. N. Wang, D. C. Qiang, L. L. Fan (all HNAS), Y. J. Yang (NYUAD), H.-W. Lin (UMich), K. W. Smith, H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, C. Angus, A. Aamer (all QUB), T. Moore (STScI), A. Schultz and M. Huber (both IfA, Hawaii) report:
As part of the Kinder collaboration (Chen et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428), we conducted follow-up observations of the Gamma-ray Burst, GRB 261007A / fast X-ray transient EP261007a (Goto et al., GCN 45824; Malacaria et al., GCN 45830; Wen et al., GCN 45828). Imaging was acquired in the r-band using the 1m LOT and in the i-band using the 40cm SLT. The first LOT epoch of observations in r-band started at 14:01 UTC on the 07th of October 2026 (MJD 61320.5813), 21.35 hr after the EP-WXT detection.
We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 images using the 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm on individual frames. The optical counterpart (Zheng et al., GCN 45825; Mohan et al., GCN 45832; Saccardi et al., GCN 45837; Shi et al., GCN 45838; An et al., GCN 45840; Arya et al., GCN 45841; Rehemtulla et al., GCN 45843; Ruiz-Laguna et al., GCN 45844; Angulo et al., GCN 45848; Li et al., GCN 45851) with the redshift z=2.101 (Saccardi et al., GCN 45829) was clearly detected in both bands.
Moreover, we further used AutoPhOT to perform PSF photometry. The details of the observations and the measured photometry from the first frame of each band are as follows:
Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | Seeing | Airmass
LOT | r | 61320.5813 | 8.25 | 300 * 1 | 20.01 +/- 0.04 | 1".9 | 1.49
SLT | i | 61320.5841 | 8.32 | 300 * 1 | 19.9 +/- 0.1 | 2".1 | 1.46
The presented magnitudes are calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry J. L. et al. 2018, ApJ, 867, 105) and are not corrected for the expected Galactic foreground extinction of A_r = 0.08 mag and A_i = 0.06 mag in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69.
GCN Circular 45851
Subject
GRB 261007A / EP261007a: SVOM/VT optical observations
Date
2026-10-08T07:33:35Z (21 hours ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, Y. N. Ma, L. P. Xin, C. Wu, Y. L. Qiu, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), W. L. Zhang (PMO), X. Tian (GXU) report on behalf of the SVOM/VT team.
SVOM/VT performed observations with automatic slew to the field of GRB 261007A triggered by SVOM/ECLAIRs (sb26100701, Goto et al., GCN 45824). This burst was also detected by SVOM/GRM (Goto et al., GCN 45824), Fermi-GBM (Malacaria et al., GCN 45830) and Einstein Probe as EP261007a (Wen et al., GCN 45828). The current available VT data started at 2026-10-07T13:00:15 UTC, approximately 7.317 hr post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
The optical counterpart (Zheng et al., GCN 45825; Mohan et al., GCN 45832; Saccardi et al., GCN 45837; Shi et al., GCN 45838; An et al., GCN 45840; Arya et al., GCN 45841; Rehemtulla et al., GCN 45843; Ruiz-Laguna et al., GCN 45844; Angulo et al., GCN 45848) with the redshift z=2.101 (Saccardi et al., GCN 45829) was clearly detected in both channels.
The preliminary measurements are given in AB magnitudes and are not corrected for Galactic extinction:
Mid time | Band | Exposure Time | Brightness
15.65 hr VT_B 21*70 s 21.4+/-0.1 mag
15.66 hr VT_R 16*70 s 21.0+/-0.1 mag
The light curves show fading behavior in both channels with a slope of -1.4 for our available data spanning 7.6 hr to 15.7 hr.
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 Circular 45850
Subject
GRB 261007A: Swift-XRT afterglow detection
Date
2026-10-08T07:22:21Z (21 hours ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
K.L. Page (U. Leicester), S. Campana (INAF-OAB), A. Melandri
(INAF-OAR), T. Sbarrato (INAF-OAB), S. Dichiara (PSU), D.N. Burrows
(PSU), J.J. DeLaunay (PSU), A.P. Beardmore (U. Leicester) and P.A.
Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
SVOM/ECLAIRs-detected burst GRB 261007A, also known as EP261007a (GCN
Circ. 45828). We searched for X-ray sources in 1.9 ks of Photon
Counting (PC) mode data. The total exposure at the position of the
afterglow (see below) is 1.9 ks, obtained between T0+38.5 ks and
T0+44.0 ks.
An uncatalogued X-ray source is detected and is above the RASS 3-sigma
upper limit at this position, and is therefore likely the GRB
afterglow. The position of this source is also consistent with the
optical counterpart initially discovered by KAIT (GCN Circ. 45825).
Using 1918 s of PC mode data and 2 UVOT images, we find an enhanced XRT
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 11.61403, -17.69197 which is
equivalent to:
RA (J2000): 00h 46m 27.37s
Dec(J2000): -17d 41' 31.1"
with an uncertainty of 2.7 arcsec (radius, 90% confidence). This
position is 2.4 arcmin from the SVOM/ECLAIRs position. The light curve
is currently consistent with a constant source of mean count rate
1.3e-01 ct/sec.
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.74 (+0.29, -0.21). The
best-fitting absorption column is 3.7 (+7.0, -1.6) x 10^20 cm^-2,
consistent with the Galactic value of 2.1 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 3.7 x 10^-11 (4.0 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.7 (+7.0, -1.6) x 10^20 cm^-2
Galactic foreground: 2.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.74 (+0.29, -0.21)
The results of the XRT-team automatic analysis are available at
https://www.swift.ac.uk/xrt_products/00021917.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021917.
This circular is an official product of the Swift-XRT team.
GCN Circular 45848
Subject
GRB 261007A: SVOM/COLIBRÍ (FM-GFT) optical observations
Date
2026-10-08T06:13:36Z (a day ago)
From
Camila Angulo Valdez at UNAM <camiangulo@astro.unam.mx>
Via
Web form
Camila Angulo (UNAM), Marion Guelfand (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), , Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), report:
We imaged the field of the SVOM GRB 261007A (Goto et al., GCN Circ. 45824) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-10-08 04:57:06 to 05:41:53 UTC (from 22.5 to 23.45 hours after the trigger) and obtained 66 minutes of exposure in the r and z filters.
The data were reduced and coadded with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
We detected the optical counterpart (Zheng et al., GCN Circ. 45825; Saccardi et al., GCN Circ. 45829; Mohan et al., GCN Circ. 45832; Saccardi et al., GCN Circ. 45837; Shi et al., GCN Circ. 45838; An et al., GCN Circ. 45840; Arya et al., GCN Circ. 45841; Rehemtulla et al., GCN Circ. 45843; and Ruiz-Laguna et al., GCN Circ. 45844), at a preliminary magnitude of:
r = 21.65 +/- 0.03,
z = 21.32 +/- 0.08.
Further observations are ongoing.
We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
GCN Circular 45846
Subject
GRB 261007A / EP261007a: NuSTAR detection of prompt emission
Date
2026-10-08T02:06:16Z (a day ago)
From
Gaurav Waratkar at Caltech <gauravwaratkar@iitb.ac.in>
Via
Web form
G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group:
The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 261007A, associated with EP261007a, in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper.
The NuSTAR SINGS algorithm triggered at 2026-10-07T05:39:49.7 UTC shows a detection of GRB 261007A, detected by SVOM (GCN 45824), Fermi-GBM (GCN 45830), and associated with EP261007a detected by Einstein Probe (GCN 45828).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a two-peak burst lasting for about 30-s, consistent with the GBM lightcurve. The peak count rate is ~4000-cps with a baseline rate of ~1000-cps during this time period. We also see a detection in the signal above 100 keV in the CZT detectors.
The optical counterpart (GCN 45825) at RA = 11.6142, Dec = -17.6922 implies an offset from the NuSTAR boresight of 87-deg and an offset from the geocenter of 78-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/261007A
Information on NuSTAR SINGS can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/
NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington.
GCN Circular 45844
Subject
GRB 261007A / EP261007a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm telescope at McDonald Observatory
Date
2026-10-07T21:42:30Z (a day ago)
From
Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>
Via
Web form
E. Ruiz-Laguna, S. Abad Gómez, K.N. Alvez Báez, G. de la Mata Nú ñez, J. Díaz-Miguel Font, A. Fernández-Roselló, L. García Rodríguez, S. M. Holtham, R. Jiménez Rioja, H. Morín-González, L. Ortega-Barcenilla, C. Pasamontes-Duarte, M. Ríos-Jiménez, S.J. Riquelme-Salinas, L. Rodríguez-Torres, A. Rosendo Pato, I. Ruiz-Pérez, D. Zazo-Callejas (all ULL), S. R. Berlanas (IAC and ULL),
and I. Pérez-Fournon (IAC and ULL)
We report on observations of the optical counterpart of GRB 261007A detected by SVOM/ECLAIRs and SVOM/GRM (Goto et al., GCN 45824), Einstein Probe WXT and FXT (EP261007a, Wen et al., GCN 45828), and Fermi GBM (Malacaria, GCN 45830).
We observed the field of GRB 261007A / EP261007a with a Las Cumbres Observatory (LCO) 40-cm telescope
located at the LCO node at McDonald Observatory, Texas, with 180-sec exposures in each of the SDSS g´, r´, and i' filters. The first observation started on 2026-10-07 at 07:07:24 UT, about 1.4225 hr after the SVOM trigger. The optical counterpart first detected with KAIT by Zheng et al. (GCN 45825) is clearly detected in all bands. We measure the following AB magnitudes, calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction:
Date (UT, mid-time) | filter | mag | error | mid t - t0 (hr)
-----------------------------------------------------------------------
2026-10-07T07:08:54 | g' | 18.59 | 0.06 | 1.4475
2026-10-07T07:12:04 | r' | 18.33 | 0.08 | 1.5003
2026-10-07T07:15:11 | i' | 18.10 | 0.16 | 1.5522
Our results are consistent with other optical and near-IR detections: Saccardi et al. (GCN 45829, spectroscopic redshift of 2.101), Mohan et al. (GCN 45832), Saccardi et al. (GCN 45837), Shi et al. (GCN 45838), An et al. (GCN 45840), Arya et al. (GCN 45841), Rehemtulla et al. (ZTF26abzxgsr, GCN 45843), and Fracile et al. (AT 2026aepi, TNS Astronomical Transient Report No. 327228).
Based on observations made with the Las Cumbres Observatory’s education network telescopes that were upgraded through generous support from the Gordon and Betty Moore Foundation (LCO program IAC2026B-010).
These observations are part of a course in Astrophysical Techniques of the Master in Astrophysics of the Astrophysics Department of the University of La Laguna in collaboration with the Instituto de Astrofísica de Canarias (La Laguna, Tenerife, Canary Islands, Spain).
GCN Circular 45843
Subject
GRB 261007A: Autonomous identification and follow-up of the counterpart to GRB 261007A by BTSbot with ZTF and P60/SEDM
Date
2026-10-07T19:34:48Z (a day ago)
Edited On
2026-10-08T13:13:29Z (15 hours ago)
From
Nabeel Rehemtulla at Northwestern University <nabeelrehemtulla2027@u.northwestern.edu>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of Nabeel Rehemtulla at Northwestern University <nabeelrehemtulla2027@u.northwestern.edu>
Via
Web form
Nabeel Rehemtulla, Gokul Srinivasaragavan, Adam A. Miller, Ved G. Shah (Northwestern, CIERA), Tomas Ahumada (NOIRLab), Antoine Le Calloch, Michael W. Coughlin, Michael C. Davis (UMN), Igor Andreoni, Anirudh Salgundi, and James Freeburn (UNC) report on behalf of the ZTF collaboration:
We report on ZTF and P60/SEDM follow-up of the optical counterpart (Zheng et al., GCN 45825; Saccardi et al., GCN 45829; Mohan et al., GCN 45832; Saccardi et al., GCN 45837, Shi et al., GCN 45838, Arya et al., GCN 45841) to GRB 261007A (Goto et al., GCN 45824).
The counterpart was automatically discovered in ZTF data by the BTSbot machine learning model (Rehemtulla et al. 2024) at 2026-10-07 08:14, independent of the GRB trigger. BTSbot autonomously requested P60/SEDM follow-up, which was carried out 34 minutes later (2026-10-07 08:48). The SEDM spectrum is at ultra low-resolution (R~100) and shows only a continuum. ZTFReST (Andreoni et al. 2021) and other fast transient filters developed within the ZTF Collaboration also identified ZTF26abzxgsr as a candidate fast transient independent of the GRB trigger.
The ZTF observations were conducted as part of the 1-day cadence public gri survey overlapping the Rubin-LSST Wide-Fast-Deep footprint. The source (ZTF26abzxgsr / AT 2026aepi) was detected in ZTF gri images and was not detected the previous night.
| Obs time (UTC) | Time since SVOM detection (2026-10-07 05:42:03) (hh:mm:ss) | Band | Alert mag (AB) | Mag unc |
|---|---|---|---|---|
| 2026-10-06 06:02:24 | - | r | >19.96 | non-det |
| 2026-10-06 08:35:41 | - | i | >19.75 | non-det |
| 2026-10-06 09:23:14 | - | g | >19.92 | non-det |
| 2026-10-07 06:02:02 | 00:19:59 | r | 17.16 | 0.032 |
| 2026-10-07 06:34:56 | 00:52:53 | i | 17.83 | 0.067 |
| 2026-10-07 07:33:02 | 01:50:59 | g | 18.84 | 0.088 |
Magnitudes are not corrected for Galactic extinction. All times are in UTC. BTSbot processes alerts in the BOOM alert broker (Jegou du Laz et al. 2026) and interfaces with follow-up facilities through the SkyPortal marshal (Coughlin et al. 2023).
Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan, and the German Center for Astrophysics (DZA), Germany. Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA.
SED Machine is based upon work supported by the National Science Foundation under Grant No. 1106171
The Gordon and Betty Moore Foundation, through both the Data-Driven Investigator Program and a dedicated grant, provided critical funding for SkyPortal.
GCN Circular 45841
Subject
GRB 261007A: GROWTH-India Telescope optical observations
Date
2026-10-07T17:21:43Z (a day ago)
From
Aditya Pawan Saikia at IIT Bombay <adityaps@iitb.ac.in>
Via
Web form
R. Arya (IITB), A. Sarkar (IITB), V. Vijaykumar (IITB), S. Patil (IITB), A.P. Saikia (IITB), V. Swain (IITB), T. Mohan (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team:
We observed the field of GRB 261007A detected by SVOM (SVOM mission Team, GCN 45824), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-10-07 15:05:35, i.e., 9.34 hours after the trigger, and obtained multiple exposures in the SDSS r' and g' filters. We detect the optical counterpart in our images at the position reported by Zheng et al., GCN 45825. The photometric results are as follows:
| MJD (mid) | Filter | tmid-t0 (hours) | Exposure Time (sec) | Magnitude (AB) |
| -------------- | ------ | --------------- | ------------------- | ---------------- |
| 61320.688 | r' | 9.603 | 4x300 | 20.11 +/- 0.06 |
| 61320.686 | g' | 10.389 | 3x300 | 20.56 +/- 0.08 |
The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.
Our results are consistent with other optical observations (An et al., GCN 45840, Saccardi et al., GCN 45829 and GCN 45837, Shi. et all, GCN 45838, and Mohan.et al. GCN 45832)
The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
GCN Circular 45840
Subject
GRB 261007A / EP261007a: TRT optical observations
Date
2026-10-07T17:03:36Z (a day ago)
From
J. An <jiean0813@foxmail.com>
Via
Web form
J. An (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), S.Y. Fu, L. Lei (HUST), L.B. He, S.Q. Jiang, X. Liu, D. Xu, Z.P. Zhu (NAOC) report:
We observed the optical afterglow (Zheng et al., GCN 45825; Saccardi et al., GCN 45829; Mohan et al., GCN 45832; Saccardi et al., GCN 45837; Shi et al., GCN 45838) of GRB 261007A detected by SVOM/ECLAIRs (Goto et al., GCN 45824), Fermi/GBM (Malacaria et al., GCN 45830), and EP/WXT (Wen et al., GCN 45828), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT). Observations started at 2026-10-07 06:00:52 UT, i.e., 18.82 min post-burst, and a series of R-band frames were obtained.
The optical afterglow is well detected in our images with a brightness of R = 17.15 +/- 0.05 at a median time of 23.3 min post-trigger, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction.
Follow-up observations are ongoing.
GCN Circular 45839
Subject
GRB 261007A: Swift ToO observations
Date
2026-10-07T16:17:46Z (a day ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the SVOM/ECLAIRs-detected event
GRB 261007A. Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021917
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the SVOM/ECLAIRs event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 45838
Subject
GRB 261007A: SVOM/C-GFT optical observations
Date
2026-10-07T15:47:18Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Y.Y. Shi(GXU), Z. Kang (CHO),S.J. Yin (GXU), C. Wu (NAOC), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC), W.L. Zhang(PMO), X. Tian(GXU) report on behalf of the SVOM/C-GFT team:
We observed the field of GRB 261007A detected by SVOM/ECLAIRs (Goto et al., GCN 45824) with LATIOS on SVOM/C-GFT. Observations started at 2026-10-07T12:54:31 UTC, ~7.21 hr after the trigger.
The optical candidate (Zheng et al., GCN 45825; Saccardi et al., GCN 45829; Mohan et al., GCN 45832; Saccardi et al., GCN 45837) was faintly detected in our stacked images of band g, r and i. The magnitude is:
| [date-obs(mid-time)] | Mid_t-T0(h) | exposure time (s) | band | mag (AB) | mag_err |
|---|---|---|---|---|---|
| 2026-10-07T13:46:09 | 8.07 | 19×100s | g | 20.35 | +/- 0.20 |
| 2026-10-07T14:02:59 | 8.35 | 20×100s | r | 20.26 | +/- 0.23 |
| 2026-10-07T13:28:38 | 7.78 | 19×100s | i | 19.93 | +/- 0.15 |
The photometry was calibrated against DESI Legacy Imaging Surveys DR10 catalogue and no correction for Galactic dust extinction was applied.
We thank the observation assistants B.-W. Li and H.-X. Xue at Jilin observatory for their excellent support.
The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcmin x 21 arcmin FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching.
GCN Circular 45837
Subject
GRB 261007A / EP261007a: LCO optical observations
Date
2026-10-07T15:16:01Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
A. Saccardi (CEA/Irfu), D. Turpin (CEA/Irfu), S. J. Yin (GXU), C. Wu (NAOC), W. Zhang(PMO), X. Tian (GXU), report on behalf of the SVOM mission team:
We observed the optical counterpart (Zheng et al., GCN 45825; Mohan et al., GCN 45832; Saccardi et al., GCN 45829) of the SVOM/ECLAIRs GRB 261007A / EP261007a (Goto et al., GCN 45824), also detected by EP/WXT (Wen et al., GCN 45828) and Fermi/GBM (Malacaria, GCN 45830), with the LCO 1m telescope at Siding Spring Observatory equipped with the Sinistro instrument.
Our observation started on 2026-10-07 at 13:00:16 UT (about 7.3 hr after the trigger) and we obtained 3x200 s exposures in the SDSS r filter.
The optical candidate is well detected in our images. We measure the following magnitude calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction:
r = 19.78 +/- 0.08 AB (mid-time 7.33 hr after the trigger).
This project is funded by the SVOM collaboration.
GCN Circular 45832
Subject
GRB 261007A: WINTER J-band observations
Date
2026-10-07T10:54:56Z (2 days ago)
From
tanishk.mohan@iitb.ac.in
Via
Web form
Tanishk Mohan (IITB), Benjamin Schneider (LAM), Geoffrey Mo (Caltech/Carnegie), Viraj Karambelkar (Columbia), Tomas Ahumada (NOIRLab), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report:
We observed the field of GRB 261007A (Goto et al., GCN 45824; also see Wen et al., GCN 45828 and Malacaria et al., 45830) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024).
Observations began on 2026-10-07 at 06:10:56.150 UTC in the J band (28.9 min after the SVOM/ECLAIRs trigger), consisting of 15*120 sec exposures. The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565).
We detect a bright source present at the optical counterpart position (Zheng et al., GCN 45825; Saccardi et al., GCN 45829) in our stacked image. We obtain the following magnitude: J = 17.36 +- 0.06 mag (AB) in our stacked image. We also note that the source has faded by ~0.5 mag between our first and last exposure during the observation (in about 28 min).
WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research.
GCN Circular 45830
Subject
GRB 261007A: Fermi GBM observation
Date
2026-10-07T09:55:08Z (2 days ago)
Edited On
2026-10-08T15:27:13Z (13 hours ago)
From
Christian Malacaria at INAF-OAR <cmalacaria.astro@gmail.com>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>
Via
Web form
C. Malacaria (INAF-OAR) report report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 05:39:49.71 UT on 07 October 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 261007A (trigger 813044394/261007236), which was also detected by SVOM/Eclairs (Hatsune Goto et al. 2026, GCN 45824), EP (W.F. Wen et al. 2026, GCN 45828), KAIT (W. Zheng et al. 2026, GCN 45825), and VLT (A. Saccardi et al. 2026, GCN 45829) with a spectroscopic redshift of z = 2.101.
The Fermi GBM on-ground location is consistent with the SVOM/Eclairs position.
The angle from the Fermi LAT boresight is 92 degrees.
The GBM light curve consists of multiple bright peaks with a duration (T90) of about 22.8 s (50-300 keV).
The time-averaged spectrum from T0 to T0+36 s is best fit by a power law function with an exponential high-energy cutoff.
The power law index is -0.61 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 300 +/- 4 keV.
The event fluence (10-1000 keV) in this time interval is (9.01 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+21.7 s in the 10-1000 keV band is 43.5 +/- 0.5 ph/s/cm^2.
A Band function fits the spectrum equally well with Epeak = 293 +/- 5 keV, alpha = -0.60 +/- 0.01 and beta = -3.3 +/- 0.3.
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/"
GCN Circular 45829
Subject
GRB 261007A / EP261007a: VLT/X-shooter spectroscopic redshift z = 2.101
Date
2026-10-07T09:42:59Z (2 days ago)
From
Andrea Saccardi at CEA/Irfu <andrea.saccardi@cea.fr>
Via
Web form
A. Saccardi (CEA/Irfu), B. Schneider (LAM), N. Habeeb (U. Leicester), D. B. Malesani (DAWN/NBI and Radboud), S. D. Vergani (LUX-Paris Obs.), M. Garnichey (LUX-Paris Obs.), J. An (NAOC), report on behalf of the Stargate collaboration:
We observed the optical counterpart (Zheng et al., GCN 45825) of the SVOM/ECLAIRs GRB 261007A (Goto et al., GCN 45824), also detected by EP/WXT (Wen et al., GCN 45828), using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph.
In a 3x15 s r-band exposure taken with the acquisition camera (1.21 hr after the SVOM trigger), the counterpart is detected with a magnitude r = 18.53 +/- 0.04 (AB), calibrated against Pan-STARRS and not corrected for Galactic extinction.
A spectrum covering the wavelength range 3000-21000 AA was secured, with a total exposure time of 2x600 s in each of the UVB, VIS, and NIR arms. Our observations started at 07:03:33 on 2026 October 7 (1.36 hr after the SVOM trigger).
In a preliminary reduction of the spectra, we clearly detect a continuum in each arm, and a broad trough at ~3770 AA, consistent with Lyman alpha. From the detection of multiple narrow absorption features, including N V, S II, Si II, Si II*, O I, O I*, Ni II, C II, C II*, C IV, Si IV, Fe II, Al II, Al III, Cr II, Zn II, Fe II*, Ni II*, Mn II, Mg II, Mg I, and Ca II, we infer a redshift of z = 2.101. The detection of fine-structure lines also confirms the physical association between this absorption system and the high-energy transient. We thus securely conclude that GRB 261007A / EP261007a is at z = 2.101.
We also detect several intervening systems, in particular a sub-DLA at z = 1.79 (Lya, Mg II, Si II, Fe II) and a system at z = 1.83 showing many absorption lines (C IV, Si IV, Fe II, Al II, Al III, Mg II, Mg I).
We acknowledge excellent support from the ESO staff in Paranal.
GCN Circular 45828
Subject
EP261007a/GRB 261007A: Einstein Probe detection of an X-ray transient
Date
2026-10-07T08:56:40Z (2 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
W.F. Wen (SZTU), Q.H. Lao, H.Y. Liu (NAO, CAS), L.N. Xu (USTC), X.H. Tang (THU) and C.C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP261007a. The transient triggered EP-WXT (ID: 01709321003) at 2026-10-07T06:47:00 (UTC). The WXT position of the source is R.A. = 11.629 deg, DEC = -17.694 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic).
A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 11.6137 deg, DEC = -17.6933 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).
We note that EP261007a is spatially consistent with GRB 261007A (GCN #45824, #45825). Further information will be updated when the telemetry data is received.
Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).
GCN Circular 45825
Subject
GRB 261007A: KAIT optical counterpart candidate
Date
2026-10-07T06:47:42Z (2 days ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
Via
email
WeiKang Zheng (UCB), Yun Wang (UCB), Xuhui Han (NAOC),
Pinpin Zhang (NAOC), and Alexei V. Filippenko (UCB) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, observed the field of SVOM GRB 261007A (Goto
et al., GCN 45824) starting at 05:43:55, 112 seconds after SVOM
trigger. Observations were performed in 3 x 3 tiling mode, and a
set of clear (roughly R) filter images were obtained. In one of
the fields, we found an optical counterpart candidate at position
of Ra,Dec=(11.6142,-17.6922 degree), which is equal to:
RA = 00:46:27.4 (J2000)
Dec= -17:41:32.0 (J2000).
The candidate decayed from 15.1 mag to 17.2 mag in our observations
separated by ~23 minutes, we suggest this to be the optical
counterpart of GRB 261007A. Observations are on going.
GCN Circular 45824
Subject
GRB 261007A: SVOM detection of a burst
Date
2026-10-07T06:31:05Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Hatsune Goto (RIKEN/CEA), Renjie Xiong(GXU), Donghua Zhao (NAOC), Wenlong Zhang(PMO), Xiao Tian(GXU), report on behalf of the SVOM mission team:
At 2026-10-07T05:42:03 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 261007A (SVOM burst-id sb26100701).
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 4 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 8.19 in the [5-20] keV energy band over a time window of 327.68 seconds starting at 2026-10-07T05:37:58.
The localization of the best alert is R.A., Dec. 11.5787, -17.6698 degrees:
R.A. (J2000) = 0h46m18.89s
Dec. (J2000) = -17d40m11.38s
with a 90% confidence level (C.L.) radius of 9.61 arcmin (including systematic error of 2 arcmin added in quadrature).
This burst also triggered SVOM/GRM at 2026-10-07T05:39:49 with an SNR of 5.30.
SVOM slewed to the burst.
The observations of MXT and VT will be reported in future circulars.
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 Xiao Tian: tianxiao@st.gxu.edu.cn.
Please contact the BA by email if you require additional information.