{
  "subject": "GRB 250901A: LCO optical upper limit",
  "circularId": 41642,
  "bibcode": "2025GCN.41642....1S",
  "submittedHow": "web",
  "body": "A. Saccardi (CEA/Irfu), B. Schneider (LAM), D. Turpin (CEA/Irfu), B. Cordier (CEA/Irfu), report on behalf of the SVOM mission team:\n\nWe observed the field of the GRB 250901A detected by SVOM/ECLAIRs (Piron et al., GCN 41634) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument.\n\nOur observation started on 2025-09-01 at 19:22:42 UT (68 minutes after the trigger) and we obtained 3x200 s exposures using the SDSS r filter. In the stacked image, we did not detect any new optical source at the position of the Swift/XRT source #1 (https://www.swift.ac.uk/SVOM/SVOM_FIELD00033/).\n\nWe derived the following upper limit r > 21.3 AB mag (3-sigma) calibrated using nearby stars from the PanSTARRS DR1 catalog and not corrected for Galactic extinction.\n\nThis project is funded by the SVOM collaboration.",
  "createdOn": 1756764120265,
  "eventId": "GRB 250901A",
  "format": "text/plain",
  "submitter": "SVOM_group <svomgroup@bao.ac.cn>"
}