GCN Circular 46063
Subject
GRB 261026A: SVOM/VT optical blue bump
Event
Date
2026-10-27T17:33:52Z (4 days ago)
Edited On
2026-10-28T00:11:52Z (3 days ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, Y. L. Qiu, C. Wu, J. Wang, Y. N. Ma, L. P. Xin, Z. H. Yao, J. R. Xu, L. J. Chen, X. H. Han, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC) and J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team.
SVOM/VT performed continuous observations for GRB 261026A (sb26102601, Goto et al., GCN 46030). The ToO observation started at 2026-10-26T16:05:47 UTC, about 9.9 hr post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
Combining earlier observations with automatic-slew data (Wu et al., GCN 46035; Li et al., GCN 46046), the afterglow (Dornic et al., GCN 46033; Zheng et al., GCN 46034; Wu et al., GCN 46035; Li et al., GCN 46046; Mohan et al., GCN 46041; Shi et al., GCN 46047; Morín-González et al., GCN 46048; Novotny et al., GCN 46049; Coyo et al., GCN 46054; Zhao et al., GCN 46056; Jiang et al., GCN 46058; Moskvitin et al., GCN 46062) exhibits a broad blue bump in the VT_B band at ~10-30 ks, with an amplitude of 0.3±0.1 mag peaking at a mid-time of approximately 5.3 hr post trigger. Preliminary analysis did not reveal a significant bump in the VT_R band at the corresponding epoch (amplitude<0.1 mag). The following measurements are in AB magnitudes and are not corrected for Galactic extinction:
Mid time | Band | Exposure Time | Brightness
28.03 h VT_B 70*34 s 22.8 +/- 0.2 mag
28.02 h VT_R 70*30 s 22.5 +/- 0.2 mag
The physical origin of this feature is currently unclear. Continuous monitoring is ongoing.
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.