{
  "bibcode": "2022GCN.31353....1F",
  "body": "S.Y. Fu (NAOC), Z.P. Zhu (NAOC, HUST), D. Xu, X. Liu, S.Q. Jiang (NAOC) \nreport on behalf of a larger collaboration:\n\nWe observed the field of GRB 220101A detected by Swift (Tohuvavohu et \nal., GCN 31347) and Fermi (Arimoto et al., GCN 31350) using the \nXinglong-2.16m telescope equipped with the BFOSC camera. Observations \nwere carried out starting at 09:50:07 UT on 2022-01-01. We firstly \nobtained 4x300 s frames in each of the B, V, R and I bands, and then \n2x1800 s spectroscopy covering ~3800 - 8800 AA.\n\nThe optical afterglow of the burst (Tohuvavohu et al., GCN 31347) is \nclearly detected in each of our stacked images in the V, R and I bands, \nbut no in the B band. Preliminary photometry is as follows:\n\nTmid-T0 (hr)   Mag     MagErr  Filter\n   5.55           >21.43       N/A      B\n   5.45            19.86        0.06      V\n   5.36            18.65        0.02      R\n   5.27            17.34        0.01      I\n\nThe spectrum is in low resolution and rather low S/N. However, a broad \nabsorption feature is evident centering at ~ 6820 AA, which can \ninterpreted as Ly_alpha absorption. Besides Ly_alpha, other weak lines \nsuch as Si II, C II, Si IV are also detected at the common redshift of z \n= 4.61. We thus conclude that z = 4.61 is likely the redshift of the GRB.\n\nWe thank the great support of the Xinglong-2.16m staff, in particular \nJunjun Jia, Yinan Zhu, Aiying Zhou, and Jie Zheng.",
  "circularId": 31353,
  "createdOn": 1641052267000,
  "email": "dxu@nao.cas.cn",
  "subject": "GRB 220101A: Xinglong-2.16m photometry and spectroscopy",
  "submitter": "Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>",
  "eventId": "GRB 220101A"
}