[vsnet-grb-info 27320] GRB 210207B: AbAO optical upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29423
SUBJECT: GRB 210207B: AbAO optical upper limit
DATE:    21/02/08 10:54:56 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), R. Ya. Inasaridze (AbAO), V. R. 
Ayvazian (AbAO),  G. V. Kapanadze (AbAO), N. Pankov (HSE, IKI)  report 
on behalf of IKI-GRB-FuN:

We observed the field of  GRB 210207B (Lien et al., GCN 29420) with 
AS-32 telescope of Abastumani observatory (AbAO) in R-filter starting on 
  2021-02-08 (UT) 02:14:17. The optical afterglow (Lien et al., GCN 
29420; Kumar et al., GCN 29421) is not detected in stacked image.

Date       UT start   t-T0    Filter  Exp.   OT    Err.  UL(3sigma)
                        (mid, days)     (s)


2021-02-08 02:14:17   0.19837  R      47*60   n/d  n/d   18.7


The photometry is based on nearby USNO-B1.0 stars
USNO-B1.0_id R2
1436-0267956 15.29
1436-0268040 15.52

The non-detection of the afterglow implies a jet break somewhere before 
of our observations, or the source of the  GRB 210207B is highly redshifted.