{
  "subject": " EP250427a / GRB 250427A: LCO optical counterpart detection",
  "submittedHow": "web",
  "bibcode": "2025GCN.40267....1P",
  "circularId": 40267,
  "createdOn": 1745771409741,
  "format": "text/plain",
  "body": "I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL)\n\nFollowing the detection of the fast X-ray transient EP250427a (Wang et al., GCN circ. 40257), detected also by Fermi-GBM, GRB 250427A (Ravasio et al., GCN circ. 40262), we observed the field with one of the two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at McDonald Observatory (Texas) in the SDSS r filter. The observation started at 2025-04-27 10:10:47 UTC, about 6.53 hours after the EP-WXT trigger. An uncatalogued source is clearly detected at the optical counterpart position first reported by Perez-Garcia et al. (GCN circ. 40259) and with other optical and near-infrared detections reported by Liu et al. (GCN circ. 40260), Becerra et al. (GCN circ. 40261), Brivio et al. (GCN circ. 40264), Chornock et al. (redshift of z = 1.519, GCN circ. 40265), and Saccardi et al. (redshift of z = 1.520,  GCN circ. 40266).\n\nWe measure the following magnitude, calibrated against Pan-STARRS DR2 stars, that is not corrected for Galactic extinction:\n\nDate       |  UT start |  mag  | error | filter | exposure time (sec)  | \n------------------------------------------------------------------------\n2025-04-27   10:10:47    18.55    0.10      r              180\n\nThis work makes use of observations from the Las Cumbres Observatory global telescope network \n(LCOGT observing programme IAC2025A-009, SGLF).",
  "eventId": "GRB 250427A",
  "submitter": "Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf@iac.es>"
}