TITLE:   GCN CIRCULAR
NUMBER:  38179
SUBJECT: GRB 241112B: SVOM/VT afterglow  detection
DATE:    24/11/12 16:52:30 GMT
FROM:    Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>

SVOM/VT commissioning team: Y. L. Qiu, H. L. Li, L. P. Xin, C. Wu, X. H. Han, 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, (NAOC), J. Zhang, L. J.  Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM), H. Zhou (PMO), C. W. Wang(IHEP), W. J. Tan(IHEP), R. C. Chen(NJU).

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 GRB 241112B (Yang et al., GCN 38173) was observed by on-board VT after the automatic slew of the platform. The VT conducted observations in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. 

An uncatalogued source was detected in data processing results on-board in VT_B and VT_R band images within the errorbox of Eclairs (Yang et al., GCN 38173), and further confirmed with the data downlinked via X band. The source is located near a faint extended source in DESI Dr10 catalog, and its brightness was fading for 3.5 magnitudes in VT_B images in the initial 5.5 hours.

The magnitude was VT_B=18.24 mag and VT_R=17.70 mag in AB magnitude at 2024-11-12T11:04:59 UT, about 7.6 min after the burst.

The coordinates are R.A.= 01:56:09.270, DEC. = 09:06:27.91, Error = 0.1 arcseconds, J2000.

We proposed that this source is the optical counterpart 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 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.