GCN Circular 30757
Subject
GRB 210820A: TSHAO optical upper limit
Date
2021-09-03T17:11:38Z (3 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), I. Reva (FAP), A. Kusakin (FAP), A. Pozanenko (IKI),
N.Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:
We observed GRB 210820A (Beardmore et al., GCN 30664) with Zeiss-1000
telescope of Tien Shan Astronomical Observatory starting on Aug. 21 (UT)
21:32:02.
The optical afterglow (Beardmore et al., GCN 30664; Lipunov et al., GCN
30666; Fu et al., GCN 30669; Zhu et al., GCN 30670; Butler et al., GCN
30672; Strausbaugh et al., GCN 30673; Blazek et al., GCN 30674; Laha et
al., GCN 30675; LaPorte and Beardmore, GCN 30686; Komesh et al., GCN
30688; Guelbenzu et al., GCN 30695; Kann et al., GCN 30731) was not
detected in the stacked image down to a limiting magnitude of 21.8 in R
filter. Preliminary photometry of the field in a stacked image is following.
Date UT start t-T0 Filter Exp. OT Err. UL(3 sigma)
(mid, days) (s)
2021-08-21 21:32:02 1.17659 R 27*90 n/d n/d 21.8
The photometry is based on nearby USNO-B1.0 stars.
USNO-B1.0
RA Dec R2
01:22:01.52088 +04:35:30.2028 17.48
01:22:14.95944 +04:43:31.2204 17.89