{
  "bibcode": "2018GCN.22804....1Z",
  "body": "Z.P. Zhu, D. Xu, J.B. Zhang (NAOC), X. Zhang, J.H. Liu (XAO), Z.B. Dai \n(YNAO) report:\n\nWe observed the field of GRB 180618A (LaPorte et al., GCN 22790) using \nthe 2.16-m telescope located at Xinglong, Hebei, China, equipped with \nthe BFOSC camera. We obtained 6x600s R-band frames, starting at 12:43:22 \nUT on 2018-06-19, i.e., 1.50 days after the BAT trigger.\n\nThe previously detected optical afterglow of the GRB (e.g., LaPorte et \nal., GCN 22790; Guidorzi et al., GCN 22792; Tyurina et al., GCN 22797) \nwas not present in our stacked image, down to a limiting magnitude of \nR~21.4 mag, calibrated with the SDSS field.",
  "circularId": 22804,
  "createdOn": 1529499722000,
  "email": "dxu@nao.cas.cn",
  "subject": "GRB 180618A: Xinglong-2.16m optical upper limit",
  "submitter": "Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>",
  "eventId": "GRB 180618A"
}