TITLE: GCN CIRCULAR NUMBER: 41144 SUBJECT: SVOM J195836+32283/sb25072103: Second VT observation DATE: 25/07/23 16:24:40 GMT FROM: Liping Xin at NAOC, SVOM xlp@nao.cas.cn

L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei, D.H. Zhao (NAOC), J. Palmerio (CEA) report on behalf of the SVOM team:

SVOM/VT performed a second ToO observation for the galactic transient SVOM J195836+32283 (sb25072103) (Gotz et al., GCN 41131) detected by SVOM/MXT. The VT conducted observations between July 22, 2025, 11:23:37 UT and 15:18:41 UT, from 26.7 hours 30.6 hours after trigger time in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.

For the optical source identified in VT observation (Gotz et al., GCN 41131), its brightness was 22.2+/-0.3 mag in our second observations. No apparent variability was detected compared to the first VT observation.

Given the constant brightness in our twice observations, it is likely that this object is the extended source as noticed by Mo et al. (GCN 41138) and Eyles-Ferris et al. (GCN 41143).

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.

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