{
  "eventId": "GRB 250309B",
  "submittedHow": "web",
  "body": "S.Q. Jiang (NAOC), S.H. Wang (THU), J. An, X. Liu, Z.P. Zhu, D. Xu (NAOC), S.Y. Fu (HUST), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:\n\nWe observed the optical counterpart AT2025dws (Stein et al., GCN 39639, 39644; Pérez-Fournon et al., GCN 39643; Moskvitin et al., GCN 39645, 39658; Perley et al., GCN 39646; Malesani et al., GCN 39647; Page and Evans, GCN 39649; Ducoin et al., GCN 39650; Shin et al., GCN 39654; Wang et al., GCN 39661; Guiffreda et al., GCN 39670) of GRB 250309B (GBM team, GCN 39635; Preis and Greiner, GCN 39629; McDermott et al., GCN 39642; Wang et al., GCN 39648; Kozyrev et al., GCN 39652; Frederiks et al., GCN 39655), using the 0.33 m diameter telescope RC-10 located at Daochen, Sichuan, China. Observations started at 18:53:25.836 on 2025-03-09, i.e., 11.247 hrs after the Fermi/GBM trigger time, a series of 600 s frames in sloan r-band were obtained.\n\nThe optical transient was detected in our stacked image with mag_r= 19.7 +/- 0.2 at a median time of 12.260 hrs after the trigger time, calibrated with the nearby Pan-STARRS field and not corrected for Galactic extinction.",
  "editedOn": 1741799542263,
  "circularId": 39687,
  "subject": "GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation",
  "format": "text/plain",
  "createdOn": 1741798904249,
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of sqjiang at NAOC <sqjiang@bao.ac.cn>",
  "bibcode": "2025GCN.39687....1J",
  "submitter": "sqjiang at NAOC <sqjiang@bao.ac.cn>",
  "version": 2
}