TITLE: GCN CIRCULAR NUMBER: 41250 SUBJECT: GRB 250806A: SVOM/VT refined analysis DATE: 25/08/06 15:26:59 GMT FROM: Liping Xin at NAOC, SVOM xlp@nao.cas.cn

L. P. Xin, H. L. Li, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, 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. Palmerio (CEA) report on behalf of the SVOM mission team.   SVOM/VT performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Xie et al., GCN 41243) in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.

No uncatalogued candidates were detected in our single or stacked images within the errorbox of the Swift/XRT position (Campana et al., GCN 41249) in the X-band downlinked data, comparing to Legacy survey. The 3 sigma upper limits are:

[T-T0, mid-time] | exposure time (s) | band | upper limit (AB) ----------- -----|-------------------|------|----------------- 377 | 9*50 | VT_B | 23.3 3293 | 59*50 | VT_B | 23.6 377 | 9*50 | VT_R | 22.9 3293 | 59*50 | VT_R | 23.2

Our photometry are not corrected for the Galactic extinction.

Our results are consistent with non-detection of optical candidate (Wu et al., GCN 41244, Fortin et al., GCN 41245, Freeberg et al., GCN 41247)

NIR follow-ups are encouraged to investigate the nature of the burst.

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre 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.   The Burst Advocate (BA) on shift for this alert is Wenjin Xie (xiewj@bao.ac.cn)

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