{
  "format": "text/plain",
  "bibcode": "2025GCN.41998....1L",
  "editedOn": 1758901433172,
  "createdOn": 1758879885268,
  "circularId": 41998,
  "submitter": "liuxing@nao.cas.cn",
  "submittedHow": "web",
  "eventId": "GRB 250925A",
  "subject": "GRB 250925A: JinShan optical observations",
  "version": 2,
  "body": "GRB 250925A: JinShan optical observations\n\nX. Liu (NAOC), S.Y. Fu (HUST) S.Q. Jiang, J. An, Z.P. Zhu, D. Xu (NAOC), A.D. Zhu, L. Lei (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration:\n\nWe observed the field of GRB 250925A detected by Swift/BAT (Dichiara, GCN 41985), using the 100cm-A (100A) and 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. The 100A observation automatically started at 17:05:21.07 UT on 2025-09-25, i.e., 54.57 seconds after the BAT trigger, and the 100C observation started one hour later. A series of frames were obtained in the Sloan r- and z- bands.\n\nThe reported optical afterglow (Corcoran et al., GCN41990; Bochenek et al., GCN 41991; Masi et al., GCN 41992; Méndez et al., GCN 41995; Méndez et al., GCN 41995) was detected in our stacked 100C images in both r- and z- bands. Preliminary photometric results are as follows:\n\nT-mid (hr) | Filter | Exposure | Mag\n2.05       |    z   |  24x180s | 20.26 +/- 0.15\n3.02       |    r   |  8x200s  | 22.10 +/- 0.20\n\ncalibrated with nearby Pan-STARRS1 DR2 stars without the Galactic extinction correction.\n\nWe acknowledge the excellent support from T.Q. Chen and J.F. Zhang for enabling these observations.",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of liuxing@nao.cas.cn"
}