{
  "body": "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, Z. H. Yao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM),T. Bouchet, D. Turpin (CEA)\n\nSVOM 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)\n\nreport on behalf of the SVOM team:\n\nThe SVOM/VT conducted a ToO follow-up observations for GRB 250103B triggered by both Swift(R. A. J. Eyles-Ferris, GCN 38796) and SVOM (T. Bouchet, GCN 38797) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously, from 2.467 hours to 7.573 hours after the burst. \n\nAn uncatalogued fading source was clearly detected within the errorbox of XRT (R. A. J. Eyles-Ferris, GCN 38796) in both VT_B and VT_R stacked images, compared to  DESI DR10 catalog. The brightness of the source was estimated to be VT_B=22.1+/-0.1 mag and VT_R=21.8+/-0.1 mag in AB magnitude at the mid time of 2.79 hours post the burst, with a total exposure time of 23*100 seconds. \n\nThe source is located at RA, Dec =  54.66373, -33.74927 deg, which is equivalent to:\nRA (J2000) : 03:38:39.30\nDec (J2000): -33:44:57.4\nwith an uncertainty of 0.2 arcsec.\n\nWe proposed that the source is the counterpart for the gamma-ray burst. \n\nMore deep follow-ups are encouraged.\n\nThe magnitudes give above are not corrected for the expected Galactic foreground extinction, corresponding to a reddening of E(B-V) = 0.0067 mag in the direction of the optical counterpart (Schlafly & Finkbeiner 2011).\n\nThe 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.",
  "circularId": 38813,
  "submittedHow": "web",
  "format": "text/plain",
  "subject": "GRB 250103B：SVOM/VT optical counterpart",
  "createdOn": 1735959267737,
  "eventId": "GRB 250103B",
  "submitter": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
  "bibcode": "2025GCN.38813....1S"
}