GCN Circular 44168
Subject
GRB 260330B: SVOM/VT optical upper limits
Event
Date
2026-03-31T15:25:54Z (7 days ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, Y. N. Ma, C. Wu, Z. H. Yao, Y. L. Qiu, J. R. Xu, L. P. Xin, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), G. X. Lan, S. Guillot (IRAP) report on behalf of the SVOM/VT team.
SVOM/VT performed observations with automatic slew to the field of GRB 260330B detected by SVOM/ECLAIRs and SVOM/GRM (sb26033003, Lan et al., GCN 44157). It was also a sub-threshold detection by Fermi/GBM (Trigg et al., GCN 44159). The observation started at 2026-03-30T15:06:18 UTC, i.e., about 46 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
No credible sources were detected within the error box of ECLAIRs (Lan et al., GCN 44157), compared to the Legacy Survey. The 5 sigma upper limits in AB magnitude are derived as follows:
Mid time | Band | Exposure Time | 5 sigma upper limit
1.03 hour VT_B 38*50 sec > 22.7 mag
1.00 hour VT_R 34*50 sec > 22.5 mag
Our photometry was in AB magnitude and was not corrected for Galactic extinction.
This result is consistent with the nondetection report by LCO (Turpin et al., GCN 44158). More detailed analysis 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.