{
  "bibcode": "2021GCN.29531....1X",
  "body": "L. P. Xin(NAOC),  J. Wang(GXU), C. Gao(GXU), X. H. Han(NAOC), J. Y. Wei(NAOC), \nG. W. LI(NAOC),  L. H. Li(NAOC), C. Wu(NAOC),  X. G. Wang(GXU), \nE. W. Liang (GXU), R. S. Zhang(NAOC), Y. L. Qiu(NAOC), \nand J. S. Deng(NAOC) report: \n\nWe began to observe GRB 210218A (Sbarufatti al., GCN 29529)\nwith Xinglong GWAC-F60A telescope, China, at 11:37:45 (UT), \n18th. Feb. 2021, about 146 sec after the burst, under bad seeing condition. \n\nA series of  R, I images were obtained.\nPreliminary analysis shows that no any new optical source\nwas found in single images within the Swift errorbox (Sbarufatti al., GCN 29529), \ndown to the 3 sigma upper limit of 15.0 mag in R band.\nThe upper limit is calibrated to the USNO B1.0 catalog.\n\nThis result is consistent with the previous report (Zhu et al., GCN 29530).",
  "circularId": 29531,
  "createdOn": 1613659323000,
  "email": "xlp@nao.cas.cn",
  "subject": "GRB 210218A： GWAC-F60A optical upper limit",
  "submitter": "Liping Xin at NAOC, SVOM  <xlp@nao.cas.cn>",
  "eventId": "GRB 210218A"
}