{
  "body": "S.Q. Jiang (NAOC), S.Y. Fu (HUST), J. An, X. Liu, L.B. He, Z.P. Zhu, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:\n\nWe observed the field of GRB 251103B detected by Swift/BAT (Lanava et al., GCN 42556) and Fermi/GBM (Fermi GBM team, GCN 42555) using the HMT-0.5m telescope located at Nanshan, Xinjiang, China. Observations started at 22:31:33 UT on 2025-11-03, i.e., 5.749 hrs after the Swift/BAT trigger, we obtained 25x120 s unfiltered frames.\nNo new optical source is detected in our stacked image within the enhanced XRT error circle (Evans et al., GCN 42558), down to the following 3-sigma limiting magnitude R>20.4 at 6.276 hrs post-burst, calibrated with the nearby PanSTARRS field and the magnitude is not corrected for Galactic extinction.",
  "format": "text/plain",
  "submitter": "sqjiang at NAOC <sqjiang@bao.ac.cn>",
  "eventId": "GRB 251103B",
  "subject": "GRB 251103B: Nanshan/HMT optical upper limit",
  "circularId": 42570,
  "createdOn": 1762237168913,
  "submittedHow": "web",
  "bibcode": "2025GCN.42570....1J"
}