TITLE:   GCN CIRCULAR
NUMBER:  30294
SUBJECT: GRB 210619B: NOT optical observations
DATE:    21/06/21 16:41:37 GMT
FROM:    Dong Xu at NAOC/CAS  <dxu@nao.cas.cn>

Z.P. Zhu (NAOC, HUST), A. de Ugarte Postigo (HETH, IAA-CSIC), D. B. 
Malesani (DTU Space), L. Izzo (DARK/NBI), D. Alexander Kann (HETH, 
IAA-CSIC), D. Xu (NAOC), A. Amanda Djupvik (NOT) report on behalf of a 
larger collaboration:

We observed GRB 210619B detected by Swift/BAT (D'Avanzo et al., GCN 
30261) with the Nordic Optical Telescope (NOT) equipped with StanCAM. 
Observations started at 04:16:27 UT on 2021-06-21, and we obtained 3x300 
s exposures in the Bessel R filter, 5x200 s in the SDSS z-filter, and 
3x300 s in the i-filter (similar to SDSS i).

The previously reported optical afterglow (e.g., Lipunov et al. GCN 
30259; Zhao et al. GCN 30261; Jelinek et al. GCN 30263; Kong et al. GCN 
30265; Axelsson et al. GCN 30270; Perley et al. GCN 30271; de Ugarte 
Postigo et al. GCN 30272; Zheng et al. GCN 30273; Blazek et al. GCN 
30274; Kann et al. GCN 30275; Svinkin et al. GCN 30276; Xin et al. GCN 
30277; Shrestha et al. GCN 30280; Jelinek et al. GCN 30281; Kumar et 
al., GCN 30286; D'Avanzo et al., GCN 30288; D'Avanzo et al., GCN 30289; 
Moskvitin et al., GCN 30291; GCN 30292) is clearly detected in our 
images. Preliminary photometric results are as follows:

T_mid/d  Filter	 Mag	   MagErr	MagSysten
1.18338	R	19.92      0.02	    Vega
1.21390	i	19.65      0.02	     AB
1.20022	z	18.88      0.11	     AB

calibrated by the PS1 catalogue.