TITLE: GCN CIRCULAR NUMBER: 42141 SUBJECT: GRB 251006B/EP251006a: SVOM/VT optical candidate DATE: 25/10/07 14:11:15 GMT FROM: Liping Xin at NAOC, SVOM xlp@nao.cas.cn
L. P. Xin, H. L. Li, Y. L. Qiu, C. Wu, Z. H. Yao, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), Z. Q. Wang, K. Liu (GXU) report on behalf of the SVOM/VT team.
SVOM/VT conducted ToO follow-up observations of GRB 251006B / EP251006a (Fermi GBM Team, GCN 42131; Yin et al. GCN 42137; Wang et al., GCN 42139). The observation started on 2025-10-07T09:37:56 UT (i.e. 13.56 hour after Fermi trigger time) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously.
Within the error box of EP-FXT source 2 (Yin et al., GCN 42140), an uncatalogued source was detected, compared to the Legacy survey. The position is at R.A., Dec. = 40.518487, -6.034955 degrees, equivalent to: R.A. (J2000) = 02:42:04.43 Dec. (J2000) = -06:02:05.8 with an uncertainty of 0.5 arcsec.
The magnitudes of the candidate are given below:
Mid_time Band Exposure Time Magnitude (AB) 13.5672 hour VT_B 41*70 sec 22.37+/-0.11 mag 13.5672 hour VT_R 39*70 sec 22.12+/-0.12 mag
Our photometry is in AB magnitude and not corrected for Galactic extinction.
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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