GCN Circular 40991
Subject
GRB 250706B: TRT bright optical counterpart detection
Event
Date
2025-07-06T18:32:19Z (a day ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Via
Web form
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.