TITLE: GCN CIRCULAR NUMBER: 40412 SUBJECT: EP250508a: SVOM/VT optical candidate fading DATE: 25/05/10 01:53:50 GMT FROM: Huali Li at at NAOC, SVOM lhl@nao.cas.cn
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, 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, T. Zhao, R. D. Liang, H. Q. Cheng, W. D. Zhang (NAOC, CAS), Y. D. Hu (GXU), L. Zhang (IHEP), X. L. Chen(YNU) report on behalf of the SVOM and EP Teams:
SVOM/VT made a second ToO observation for EP250508a (Liang et al., GCN 40390，Zhao et al., GCN 40399) at about 29.44 hour after trigger. The observation was performed in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
The brightness of the candidate reported by Xin et al. (GCN 40402) was VT_R=23.9+/-0.3 mag and VT_B>24.0 with the exposure time of 52*100 seconds.
Our photometry was derived in AB magnitude and not corrected for Galactic extinction.
Considering the fading behavior of the candidate, we suggest that it is the optical counterpart of the transient.
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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