TITLE: GCN CIRCULAR NUMBER: 38852 SUBJECT: GRB 250108A:SVOM/VT optical candidate DATE: 25/01/08 16:14:39 GMT FROM: Liping Xin at NAOC, SVOM xlp@nao.cas.cn
SVOM/VT commissioning team: Y. L. Qiu, H. L. Li (NAOC), W. K. Zheng (UCB), Z. Q. Wang (GXU), X. H. Han, L. P. Xin, C. Wu, J. Wang, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, Z. H. Yao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM)
SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV)
report on behalf of the SVOM team:
The SVOM/VT conducted follow-up observations of the GRB 250108A (Zheng et al., GCN 38845) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously.
With the X band downlinked data, an uncatalogued optical source was detected within the errorbox of MXT (Zheng et al., GCN 38845) in VT_R stacked image, compared to the DESI catalog. It is the only new source within the error box down to the 3 sigma limit of about 22.7 mag.
The brightness of the source was estimated to be 22.1+/-0.2 mag in AB magnitude in VT_R image at the mid time of 1.516 hours post the burst, with a total exposure time of 8*100 seconds. The source can not be detected in VT_R 19*100 sec stacked image with a 3 sigma limit of 23.0 mag at the middle time of 3.978 hours.
The source is located at RA, Dec = 207.89654, 26.23741, which is equivalent to: RA (J2000) : 13:51:35.17 Dec (J2000): +26:14:14.68 with an uncertainty of 0.5 arcsec.
Additionally, no any new sources were detected within the errorbox of XRT #1 source (Phil Evans et al., GCN 38846).
We proposed that this source is the candidate for the gamma-ray burst.
More deep follow-ups are encouraged to confirm the nature of the source.
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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