TITLE: GCN CIRCULAR NUMBER: 38545 SUBJECT: GRB 241212A : SVOM/VT bright optical afterglow DATE: 24/12/12 20:40:17 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, J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM), H. Zhou (PMO), Li Zhang (IHEP) 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 241212A (Zhang et al., GCN 38541; Fermi GBM team et al., GCN 38540) was observed by on-board SVOM/VT after the automatic slew of the platform. The VT conducted observations in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously. With the X band downlinked data, an uncatalogued optical source was detected in VT_B and VT_R band images within the errorbox in both Eclairs and MXT (Zhang et al., GCN 38541) compared to the Desi D10 catalog. The source is located at RA, Dec = 45.08033, 6.71682, which is equivalent to: RA (J2000) : 03:00:19.28 Dec (J2000): +06:43:00.56 with an uncertainty of 0.2 arcsec. Its brightness was fading for 1.1 magnitude in both of VT_B and VT_R images from 0.7 hours to 4.8 hours after the burst. The magnitude was VT_B = 20.60 mag and VT_R = 19.88 mag in AB magnitude,about 1.15 hr post the trigger. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/38545. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...