TITLE:   GCN CIRCULAR
NUMBER:  37503
SUBJECT: GRB 240910A:  SVOM/VT optical observations
DATE:    24/09/14 12:52:54 GMT
FROM:    Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>

SVOM/VT commissioning team: Y. L.Qiu, L. P. Xin, H. L. Li, C. Wu, X. H. Han, 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) and  Palmerio, J. (CEA).

SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Jean-Luc Atteia (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), 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), Bing Zhang (UNLV)

report on behalf of the SVOM team:

During the commissioning phase of SVOM mission, we observed the field of the GRB 240910A (Fermi team, GCN 37441, Zhang et al. GCN 37445) with SVOM/VT telescope in ToO mode. The observation started at 2024-09-12T13:51:13 UT, about 57.8 hours after the burst, and lasted for about 2.7 ks. VT made the observations with two channels simultaneously, VT_B (400nm-650nm) and VT_R (650nm-1000nm). 

The optical afterglow (Julakanti et al. GCN 37459; Jiang et al., GCN 37460; Malesani et al. GCN 37463; de Ugarte Postigo et al., GCN 37467) was detected in the VT stacked images, the magnitudes obtained by VT were: VT_B=22.24+/-0.07 mag, and VT_R=21.50+/-0.05 mag in AB magnitude.

More detailed analysis is ongoing.
 
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 is an optical telescope on board SVOM with an aperture of 44 cm, designed to automatically follow the Eclairs triggers. It has two channels: VT_B and VT_R, covering wavelengths from 400 nm to 650 nm and 650 nm to 1000 nm, respectively. The two bands are observed simultaneously. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS.