{
  "circularId": 39449,
  "format": "text/plain",
  "subject": "EP250223a: TRT optical afterglow observation",
  "submitter": "sqjiang at NAOC <sqjiang@bao.ac.cn>",
  "createdOn": 1740396863552,
  "eventId": "EP250223a",
  "bibcode": "2025GCN.39449....1A",
  "body": "J. An, S.Q. Jiang, N.C. Sun (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), Z. Fan, W.X. Li, Y.N. Wang, D. Xu (NAOC) report on behalf of a large collaboration:\n\nWe observed the field of EP250223a detected by EP (Lian et al., GCN 39429; Wang et al., GCN 39448), and observed by Swift/XRT (Kennea et al., GCN 39437), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 00:37:15.66 UTC on 2025-02-24, i.e., 9.544 hrs after the EP trigger, and a series of 200 s frames were obtained in B, V, R and I bands.\n\nThe optical afterglow (Wu et al., GCN 39439; Guo et al., GCN 39447; Izzo et al., GCN 39441; Xin et al., GCN 39445; Pérez-Fournon et al., GCN 39440; Hauptmann et al., GCN 39436; Levan et al., GCN 39438) is clearly detected in our stacked images with:\n|  T (mid) - T0 (hours)| band | mag | error  |\n|    9.816    |   B   |   21.32   |   0.14   |\n|    9.996    |   V   |   20.17   |   0.07   |\n|    10.176   |   R   |   19.86   |   0.07   |\n|    10.356   |   I   |   19.41   |   0.12   |\ncalibrated with Panstarrs-DR2 stars in the field and not corrected for Galactic extinction.",
  "submittedHow": "web"
}