{
  "circularId": 44624,
  "eventId": "GRB 260515A",
  "submitter": "SVOM_group <svomgroup@bao.ac.cn>",
  "body": "A. Saccardi, J. T. Palmerio (CEA/Irfu), Y. L. Qiu, C. Wu, L. P. Xin (NAOC)\non behalf of the SVOM/VT team.\n\nAfter the trigger by SVOM/ECLAIRs at 2026-05-15T19:08:19 UTC (T0), SVOM performed an automatic slew on the burst location (Brunet et al., GCN 44622). SVOM/VT began observing the field at 2026-05-15T19:12:34, 254.71 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.\n\nFrom a preliminary analysis of the 1-bit subimage and source list downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below.\n\nVT_ID 32:\n  The position of this candidate is R.A., Dec. 227.6852, 24.5562 degrees, corresponding to:\n  R.A. (J2000) = 15h10m44.4s\n  Dec. (J2000) = 24d33m22.4s\n  with an uncertainty of 0.50 arcsec.\n  This location is consistent with the optical afterglow reported by He et al. (GCN 44623).\n  \n  This candidate was detected in both VT_R and VT_Band was flagged as an uncatalogued source. The candidate's magnitudes are:\n\n  | date-obs (UTC)       | mid-time    | exposure  | VT_B mag(AB)  | VT_R mag(AB)  |\n  | -------------------- | ----------- | --------- | ------------- | ------------- |\n  | 2026-05-15T19:12:34  | 5.08 min    | 2*50 sec  | 16.16 ± 0.01  | 15.78 ± 0.01  |\n  \n  Magnitudes were not corrected for Galactic reddening.\n  \n  The mean color of VT_B - VT_R = 0.38 is in line with the expectations of an event at redshift z < 4.\n  \nThe Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe.\nSVOM/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.\n\nThe Burst Advocate (BA) on shift for this alert is Andrea Saccardi: andrea.saccardi@cea.fr.\nPlease contact the BA by email if you require additional information.\n",
  "format": "text/markdown",
  "subject": "GRB 260515A: SVOM/VT optical candidate from VHF data",
  "submittedHow": "web",
  "createdOn": 1778876810864,
  "bibcode": "2026GCN.44624....1S"
}