GCN Circular 30723
Subject
GRB 210822A: CAHA 2.2m observations
Event
Date
2021-08-27T00:27:10Z (4 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
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; GECAM detection: Wang et al., GCN #30678; Fermi-LAT detection:
Ohno et al., GCN #30687; AstroSat CZTI detection: Prasad et al., GCN
#30693; Konus-Wind detection: Frederiks et al., GCN #30694; GRBAlpha
detection: Ohno et al., GCN #30697) at a redshift of z = 1.736 (Zhu et
al., GCN #30692) 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; Zheng et al., GCN
#30679; Butler et al., GCN #30680; Fu et al., GCN #30684; Zhu et al.,
GCN #30692; Romanov & Lane, GCN #30701; Nicuesa Guelbenzu et al., GCN
#30703; Siegel et al., GCN #30710; Belkin et al., GCN #30712; Belkin
et al., GCN #30714) 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.