GCN Circular 45581
Subject
GRB 260915A: SVOM/VT optical upper limits
Event
Date
2026-09-15T09:42:49Z (a month ago)
Edited On
2026-09-15T12:52:13Z (a month 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. N. Ma, C. Wu, L. P. Xin, Y. L. Qiu, Z. H. Yao, J. R. Xu, L. J. Chen, 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. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team.
SVOM/VT performed an automatic slew toward the burst GRB 260915A triggered by SVOM/ECLAIRs (sb26091501, Liang et al., GCN 45570). This burst was also detected by SVOM/GRM and SVOM/MXT (Liang et al., GCN 45570). The observation started at 2026-09-15T01:16:38 UTC, i.e. 275 seconds in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With X-band telemetry data, no uncatalogued sources were identified in our stacked images within the error box of MXT (Liang et al., GCN 45570) compared to the Legacy Survey.
The following measurements are in the AB magnitude and are not corrected for Galactic extinction:
Mid time | Band | Exposure Time | 3-sigma upper limit
1.1 hr VT_B 50*50 sec > 23.6 mag
1.0 hr VT_R 50*50 sec > 23.5 mag
Our results are consistent with the non-detections from VT-VHF data (Wu et al., GCN 45575), LCO (Yin et al., GCN 45573), NOT (Zhu et al., GCN 45577), GTC (Perez-Garcia et al., GCN 45578), and SVOM/COLIBRÍ (FM-GFT) (Ducoin et al., GCN 45580).
Given the bright X-ray emission and deep early optical upper limits, this source may be a high-z GRB candidate. Near-infrared follow-up observations are encouraged.
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.