{
  "submittedHow": "web",
  "eventId": "GRB 250317B",
  "bibcode": "2025GCN.39757....1P",
  "createdOn": 1742204097453,
  "body": "I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, I. Correa-Plasencia, and A.E. Hernández-Díaz (ULL)\n\nWe report Las Cumbres Observatory Global Telescope network (LCOGT) observations of the field of GRB \n250317B, discovered by SVOM/ECLAIRs (Zhao et al., GCN circ. 39752 and GCN circ. 39753) and SVOM/MXT \n(Zhao et al., GCN circ. 39752 and GCN circ. 39753; and Götz et al., GCN circ. 39756). We observed the field of GRB 250317B with one of the two LCOGT 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at McDonald Observatory (Texas). We obtained a 300-sec exposure in the SDSS r' filter starting at 2025-03-17 07:26:01 UT, about 5.23 hours after the SVOM trigger. An uncatalogued source is clearly detected at the position of the optical afterglow detected by SVOM/F-GFT (COLIBRÍ) (Watson et al.,  GCN circ. 39754) and SVOM/VT (Palmerio et al., GCN circ. 39755).\n\nWe measure the following AB magnitude, calibrated against Pan-STARRS DR2 stars and not corrected for Galactic extinction:\n\nTime (UT, mid term)   | mag | error | filter |\n----------------------------------------------\n2025-03-17T07:28:31    19.27  0.05      r'\n\n\nThis work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF).\n",
  "subject": " GRB 250317B: LCO detection of the fading optical afterglow",
  "format": "text/plain",
  "circularId": 39757,
  "submitter": "Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>"
}