{
  "submittedHow": "web",
  "format": "text/plain",
  "submitter": "Christophe Adami at LAM <christophe.adami@lam.fr>",
  "eventId": "EP260618a",
  "circularId": 44994,
  "createdOn": 1781867146833,
  "subject": "EP260618a: OHP/T193 optical observations",
  "body": "P. Amram (LAM/Pytheas/AMU), C. Adami (LAM/Pytheas/AMU), D. Russeil (LAM/Pytheas/AMU) report on behalf of a larger collaboration:\n\nWe observed the field of EP260618a (Yang et al., GCN44978; see also Fermi GBM Team\n, GCN44973 and Jiang et al., GCN44991) using the T193cm telescope at Observatoire de Haute-Provence (France) with the MISTRAL spectro-imager. We obtained 2x10 minutes of exposure in the r-band starting at 2026-06-18T21:12:40 UT (12.63 hr after the Yang et al. trigger).\n\nIn the stacked images, the optical counterpart detected by Becerra et al. (GCN44988) and Malesani et al. (GCN44990) is visible with preliminary magnitude of:\n\nr = 21.86 +/- 0.09 mag\n\nin good agreement with their measurements.\n\nThe photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction.\n\nWe acknowledge the excellent support from Observatoire de Haute-Provence and in particular Stephane Favard. We acknowledge the excellent support of J. Schmitt and J.C. Brunel in the recent MISTRAL upgrade.\n"
}