{
  "bibcode": "2025GCN.40263....1G",
  "createdOn": 1745759134809,
  "eventId": "GRB 250424A",
  "submitter": "ankur ghosh at CAPP, University of Johannesburg <ghosh.ankur1994@gmail.com>",
  "submittedHow": "web",
  "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 250424A triggered by Swift (Cenko et al., GCN 40224), AstroSat CZTI (Harsha et al., GCN 40231), Konus-Wind (Ridnaia et al., GCN 40243) and EIRSAT-1 GMOD (McKenna et al., GCN 40249)in B, V, r  filters of  the 1-meter Sinistro 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).\n\nObservations began on , starting from 2025-04-24, 17.8 hours after the GRB trigger. Observation for later epochs are still going on.\n\nWe clearly detect the optical transient (OT) reported by GCNs (Francile et al., GCN 40222; Cenko et al., GCN 40224; Brivio et al., GCN 40225; Becerra et al., GCN 40226; Saccardi et al., GCN 40228; de Wet et al., GCN 40229; Ducoin et al., GCN 40230; and D. Turpin et al., GCN 40240, Dutton et al., GCN Circ. 40241, Siegel et al., GCN 40244)  in our B, V, r band images. \n\n------------------------------------------------------------------------------------------------------\n|Date|\t\tStart JD\t|t-T0 (hours)|\t|Exp (sec)|\t|Filter|\t|Magnitude|  \n------------------------------------------------------------------------------------------------------     \n2025-04-25\t2460790.52730\t17.78\t\t1 x 900 \tV\t\tV = 21.31+/- 0.08\n2025-04-25\t2460790.78105\t23.87\t\t1 x 900 \tB\t\tB = 22.07+/- 0.08\n2025-04-25\t2460790.79155\t24.12\t\t1 x 900\t\tr\t\tr = 21.04 +/- 0.05\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",
  "subject": "GRB 250424A: LCO optical observation",
  "format": "text/plain",
  "circularId": 40263
}