GCN Circular 42061
Subject
GRB 251002A: SVOM/VT optical observation
Event
Date
2025-10-02T20:58:44Z (6 days ago)
Edited On
2025-10-02T21:42:28Z (6 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
J. T. Palmerio, A. Saccardi, D. Götz (CEA/Irfu), H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu (NAOC) report on behalf of the SVOM/VT team:
After the trigger by SVOM/ECLAIRs at 2025-10-02T20:14:54 UTC (T0), SVOM performed an automatic slew on the burst location (Saccardi et al., GCN 42060). SVOM/VT began observing the field at 2025-10-02T20:19:44, 289.75 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 36:
This candidate was flagged as un uncatalogued source.
The position of this candidate is R.A., Dec. 13.9082, -5.5671 degrees, corresponding to:
R.A. (J2000) = 0h55m38.0s
Dec. (J2000) = -5d34m01.5s
with an uncertainty of 1 arcsec.
This location is within the R90 uncertainty region of the SVOM/MXT onboard localization.
The source was detected in both VT_R and VT_B. The candidate's magnitudes are:
| date-obs (UTC) | mid-time | exposure | band | mag(AB) |
| -------------------- | ----------- | --------- | ----- | ------------- |
| 2025-10-02T20:19:44 | 6.50 min | 4*50 sec | VT_B | 16.81 ± 0.01 |
| 2025-10-02T20:19:44 | 6.50 min | 4*50 sec | VT_R | 16.24 ± 0.01 |
Magnitudes were not corrected for dust extinction.
Given the VT color 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: jesse.palmerio@cea.fr.