GCN Circular 30723

D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, 
DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all 
HETH/IAA-CSIC), A. Fernandez, I. Hermelo, and P. Martin (all CAHA) 
report:

We observed the bright GRB 210822A (Swift detection: Page et al., GCN 
#30677
Not found
 
 
; GECAM detection: Wang et al., GCN #30678
Not found
 
 
; Fermi-LAT detection: 
Ohno et al., GCN #30687
Not found
 
 
;  AstroSat CZTI detection: Prasad et al., GCN 
#30693
Not found
 
 
; Konus-Wind detection: Frederiks et al., GCN #30694
Not found
 
 
; GRBAlpha 
detection: Ohno et al., GCN #30697
Not found
 
 
) at a redshift of z = 1.736 (Zhu et 
al., GCN #30692
Not found
 
 
) with CAFOS mounted on the 2.2m CAHA telescope at Calar 
Alto, Alemria, Spain. The first epoch was obtained under very inclement 
conditions (almost overcast), and one 60 s as well as four 90 s images 
were useful. The second epoch, two nights later, was obtained under 
significantly improved (but still not really good) conditions, and 31 x 
30 s images were obtained.

The optical afterglow (Page et al., GCN #30677
Not found
 
 
; Zheng et al., GCN 
#30679
Not found
 
 
; Butler et al., GCN #30680
Not found
 
 
; Fu et al., GCN #30684
Not found
 
 
; Zhu  et al., 
GCN #30692
Not found
 
 
; Romanov & Lane, GCN #30701
Not found
 
 
; Nicuesa Guelbenzu et al., GCN 
#30703
Not found
 
 
; Siegel et al., GCN #30710
Not found
 
 
; Belkin  et al., GCN #30712
Not found
 
 
; Belkin  
et al., GCN #30714
Not found
 
 
) is faintly detected in the first epoch, but not 
detected in the second epoch.

Against three nearby Pan-STARRS comparison stars, we measure (AB 
magnitudes):

i' = 18.56 +/- 0.14 mag at 0.43283 days after the GRB, and
i' > 21.5 mag at 2.5206 mag after the GRB.