{
  "bibcode": "2021GCN.29687....1X",
  "body": "L. P. Xin(NAOC),  C. Gao(GXU),  X. H. Han(NAOC), J. Y. Wei(NAOC), \nJ. Wang(GXU), G. W. LI(NAOC),  L. H. Li(NAOC), C. Wu(NAOC), \n X. G. Wang(GXU), E. W. Liang (GXU), Y. L. Qiu(NAOC), and J. S. Deng(NAOC) report: \n\nWe began to observe GRB 210321A (Dichiara et al. GCN \n29677; Perri et al. GCN 29678; Siegel et al. GCN 29679; Butler et \nal. GCN 29680; Heintz et al. GCN 29684; Ugarte Postigo et al., GCN 29685)\nwith Xinglong GWAC-F60A telescope, China, at 11:30:49 (UT), \n21th. Mar. 2021, about 4.28 hours after the burst. \n\nA series of  R, I images were obtained.\nThe optical counterpart ( Siegel et al. GCN 29679; Butler et al. GCN 29680; \nHeintz et al. GCN 29684; Ugarte Postigo et al., GCN 29685)\nwas clearly detected in the stacked R-band image \nobserved during 11:30:49 and 12:48:17 UT. \nThe brightness was estimated to be 18.98 +/-0.13 mag at the mean\ntime of 4.88 hours after the burst, calibrated to USNO B1.0 R2 mag, \n\n\nThis result is consistent with the previous report (Zhu et al., GCN 29530).",
  "circularId": 29687,
  "createdOn": 1616384493000,
  "email": "xlp@nao.cas.cn",
  "subject": "GRB 210321A:  Xinglong GWAC-F60A optical observation",
  "submitter": "Liping Xin at NAOC, SVOM  <xlp@nao.cas.cn>",
  "eventId": "GRB 210321A"
}