{
  "subject": "GRB 250221A: Optical counterpart detection by LCO.",
  "bibcode": "2025GCN.39425....1G",
  "body": "Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg),  Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration.\n \nWe observed the field of the GRB 250221A triggered by Swift  (Caputo et al., GCN 39396) in B, r filters of  the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Cerro Tololo Interamerican Observatory, Chille. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel).\nObservations began on February 21, 2025, starting 22.46 hours after the GRB trigger.\n\nWe clearly detect the optical transient (OT) reported by GCNs ( Francile et al., GCN 39395; Watson et al., GCN 39397; Melandri et al., GCN 39406; Shilling et al., GCN 39409; Guo et al., GCN 39412; Muenter et al., GCN 39417; Palmerio et al., GCN 39418; Pankov et al., GCN 39422; Pankov et al., GCN 39424)  in our B, r band image.\n\n|Date|\t\t|UTstart|\t|t-T0 (hours)|\t|Exp (sec)|\t|Filter|\t|Magnitude| \n----------------------------------------------------------------------------------------------------      \n2025-02-22\t 02:02:15.36\t22.46\t\t1 x 1200 \tB\t\tB = 21.91 +/- 0.06\n\n\n2025-02-22\t02:10:02.78\t22.59\t\t1 x 900 \tr\t\tr = 20.85 +/- 0.06\n----------------------------------------------------------------------------------------------------\n\n\nThe field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction.\n \n",
  "createdOn": 1740236777218,
  "circularId": 39425,
  "submitter": "ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994@gmail.com>",
  "format": "text/plain",
  "submittedHow": "web",
  "eventId": "GRB 250221A"
}