{
  "bibcode": "2025GCN.40838....1A",
  "eventId": "GRB 250625A",
  "body": "C. Adami (LAM/Pytheas/AMU), S. Basa (LAM/OHP/Pytheas/AMU), B. Schneider (LAM), E. Le Floc'h (CEA/Irfu), A. Ugarte Postigo (LAM), M. Dennefeld (IAP/CNRS/Sorbonne U.), report on behalf of a larger collaboration:\n\nWe observed the field of the GRB 250625A (Fermi GBM Team, GCN 40824; Ferro\net al., GCN 40825; Beardmore et al., GCN 40827; Dichiara et al., GCN 40835; Di Lalla\net al., GCN 40836) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 8 exposures (for a total of 81min) in the r-band starting at 20:34:39 UT on 2025-06-25 (4.50 hours after the trigger). \nWe also obtained 2 exposures (for a total of 30min) in the i-band starting at 22:28:55 UT on 2025-06-25 (6.40 hours after the trigger). \n In the stacked images, we detected the optical counterpart reported/followed by Moskvitin et al., GCN 40828, Xin et al., GCN 40830; Malesani et al., GCN 40831; Lipunov et al., GCN 40826/40832; Zhu et al., GCN 40834, Fortin et al., GCN 40837; in the r-band image. The preliminary magnitude derived for that source is:\n\nr = 22.95 +/- 0.23 mag (AB)\n\nWe do not detect the optical counterpart in the i-band image with a 3-sigma upper limit of:\ni < 22.2\n\nThe photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitudes are not corrected for Galactic extinction. We used the STDWeb/STDPipe tools (Karpov 2025).\n\n\nWe acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen and R.P. Nelson for the MISTRAL observations. ",
  "createdOn": 1750935764206,
  "submittedHow": "web",
  "submitter": "Christophe Adami at LAM <christophe.adami@lam.fr>",
  "format": "text/plain",
  "circularId": 40838,
  "subject": "GRB 250625A: OHP/T193 optical detection"
}