TITLE:   GCN CIRCULAR
NUMBER:  30492
SUBJECT: GRB 210722A: D50 optical detection
DATE:    21/07/24 08:40:09 GMT
FROM:    Martin Jelinek at Astro.Inst-AVCR,Ondrejov  <martin.jelinek@asu.cas.cz>

M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov) report:

We observed the position of the bright GRB 210722A (D'Avanzo et al., GCN
30475; Page et a., GCN 30483; Barthelmy et al. GCN 30489; and Wood, GCN
30490) with the D50 telescope of the Astronomical Institute Ondrejov, near
Prague, Czech Republic. We performed a set of 35x 60s exposures in SDSS-i'
filter on July 24 from 1:20 to 2:01 UT.

The optical afterglow (Zhu et al., GCN 30476; Pankov et al., GCN 30478 &
30488; Kumar et al., GCN 30481; Butler et al., GCN 30484; and Thoene et
al., GCN 30487) is weakly detected in the overall combined image with the
exposure mean time 28.9h after trigger. The Atlas-calibrated magnitude of
the object is i' = 19.8 +/- 0.4.