{
  "bibcode": "2025GCN.40015....1X",
  "body": "L.P. Xin, Y. L. Qiu, C. Wu, H. L. Li, J . Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, Y. N. Yi, J. Y. Wei (NAOC), J. T. Palmerio(CEA/Irfu), T. Sadibekova(CEA), X. Chen(YNU), Y. Hu(GXU) report on behalf of the SVOM team:\n\nSVOM performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Chen et al., GCN 40014). SVOM/VT began observing the field automatically with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.\n\nWith VHF downlinked data, a bright uncatalogued source was found in both channels in the first sequence, and brightening with about 0.2 mag in the second sequence, compared to DESI catalog.\n\nThe coordinates are RA, Dec = 213.40915, -5.93013 which is equivalent to:\n\nR.A.(J2000) = 14:13:38.20,\nDEC.(J2000)= -05:55:48.5\nError=0.5 arcseconds.\n\nThe brightness are VT_B ~21.53 mag(AB) and VT_R ~20.61 mag(AB) in the first sequence with the mid time of 443 seconds after the burst.\n\nWe proposed that this is the optical counterpart of the burst. Given the VT color, it is likely a low/medium redshift burst.\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.\n",
  "eventId": "GRB 250402A",
  "submittedHow": "web",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
  "createdOn": 1743639996906,
  "editedOn": 1743685764533,
  "version": 2,
  "circularId": 40015,
  "format": "text/plain",
  "submitter": "Liping Xin at NAOC, SVOM <xlp@nao.cas.cn>",
  "subject": "GRB 250402A: SVOM/VT optical counterpart"
}