{
  "bibcode": "2022GCN.32647....1X",
  "body": "D. Xu, S.Q. Jiang, S.Y. Fu, X. Liu (NAOC), Z.P. Zhu (NAOC, HUST), T.H. \nLu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:\n\nWe observed the field of the optical counterpart of Swift J1913.1+1946 \nor GRB 221009A detected by Swift (Dichiara, GCN 32632), using the \nNEXT-0.6m telescope located at Nanshan, Xinjiang, China. Observations \nstarted at 14:25:55 UT on 2022-10-09, i.e., 762 s after the Swift/BAT \ntrigger. A series of frames in the Sloan r- and z- filters were obtained.\n\nThe optical counterpart is clearly detected in each of our images, which \ndecays from r ~ 14.93 to r ~ 16.50 within ~ four hours, with a decay \nindex of \\alpha ~ 0.5 (F_t ~ t^-\\alpha), calibrated the nearby PS1 \nstars. The decaying behavior is consistent with that for conventional \nGRBs.\n\nSpectroscopy of the optical counterpart was performed at the 2.16m \ntelescope equipped with the BFOSC camera at Xinglong, Hebei, China. The \nspectrum covers the wavelength range 3800-9000 AA. The observation mid \ntime is 2022 Oct 10.63 UT, i.e., 0.95 hr after the BAT trigger.\n\nThe spectrum is dominated by a red continuum due to very high Galactic \nextinction, and no prominent absorption feature can be identified. Given \nthe detections by Swift/UVOT as well as spectral continuum, the event \ncould be real GRB 221009A at a rather low redshift.\n\nWe thank the great support of the Xinglong-2.16m staff, in particular \nJunjun Jia, Min He, Aiying Zhou, and Jie Zheng.",
  "circularId": 32647,
  "createdOn": 1665393566000,
  "email": "dxu@nao.cas.cn",
  "subject": "GRB 221009A: Nanshan/NEXT photometry and Xinglong-2.16m spectroscopy",
  "submitter": "Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>",
  "eventId": "GRB 221009A"
}