TITLE:   GCN CIRCULAR
NUMBER:  29687
SUBJECT: GRB 210321A:  Xinglong GWAC-F60A optical observation
DATE:    21/03/22 03:41:33 GMT
FROM:    Liping Xin at NAOC, SVOM  <xlp@nao.cas.cn>

L. P. Xin(NAOC),  C. Gao(GXU),  X. H. Han(NAOC), J. Y. Wei(NAOC), 
J. Wang(GXU), G. W. LI(NAOC),  L. H. Li(NAOC), C. Wu(NAOC), 
 X. G. Wang(GXU), E. W. Liang (GXU), Y. L. Qiu(NAOC), and J. S. Deng(NAOC) report: 

We began to observe GRB 210321A (Dichiara et al. GCN 
29677; Perri et al. GCN 29678; Siegel et al. GCN 29679; Butler et 
al. GCN 29680; Heintz et al. GCN 29684; Ugarte Postigo et al., GCN 29685)
with Xinglong GWAC-F60A telescope, China, at 11:30:49 (UT), 
21th. Mar. 2021, about 4.28 hours after the burst. 

A series of  R, I images were obtained.
The optical counterpart ( Siegel et al. GCN 29679; Butler et al. GCN 29680; 
Heintz et al. GCN 29684; Ugarte Postigo et al., GCN 29685)
was clearly detected in the stacked R-band image 
observed during 11:30:49 and 12:48:17 UT. 
The brightness was estimated to be 18.98 +/-0.13 mag at the mean
time of 4.88 hours after the burst, calibrated to USNO B1.0 R2 mag, 


This result is consistent with the previous report (Zhu et al., GCN 29530).