{
  "bibcode": "2022GCN.31417....1J",
  "body": "S.Q. Jiang, S.Y. Fu (NAOC), Z.P. Zhu (NAOC, HUST), X. Liu, D. Xu (NAOC), \nX. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:\n\nWe observed the field of GRB 220107B detected by Fermi (Arimoto et al., \nGCN 31409; Veres & Meegan, GCN 31414) and AstroSat (Suresh et al., GCN \n31412), using the NEXT-0.6m telescope located at Nanshan, Xinjiang, \nChina. We obtained 6x300 s frames in the Sloan r-band and 5x300 s frames \nin Sloan z-band, starting at 21:30:31 UT on 2022-01-08.\n\nNo optical source is detected in our stacked images at the Swift-XRT \nposition (Gropp et al., GCN 31411). Preliminary photometric results are \nas follows:\n\nTmid-T0 (hr)  Filter   Upper Limit(5-sigma)\n    26.97           r          >21.3\n    27.44           z          >19.3\n\ncalibrated with the nearby PanSTARRS field.\n\nIn addition, from Legacy Survey there exists a faint source at the \nborder of the Swift-XRT error circle at coordinates R.A. (J2000) = \n14:25:37.66 and Dec. (J2000) = +20:10:17.01, and magnitudes of g ~ \n24.62, r ~ 24.51, z ~ 23.32 as well as a photo_redshift = 1.13 +/- 0.23. \nThe source is not present in SDSS and PanSTARR, and might be the host of \nthe burst.",
  "circularId": 31417,
  "createdOn": 1641701087000,
  "email": "dxu@nao.cas.cn",
  "subject": "GRB 220107B: Nanshan/NEXT optical upper limits and host galaxy candidate",
  "submitter": "Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>",
  "eventId": "GRB 220107B"
}