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GCN Circular 31004

GRB 211023A: Mondy optical observations
2021-10-26T12:06:17Z (3 years ago)
Alexei Pozanenko at IKI, Moscow <>
S. Belkin (IKI), A. Pozanenko (IKI), E. Klunko (ISTP), N. Pankov (HSE), 
  report  on behalf of GRB IKI FuN:

We observed the GRB 211023A (Fermi GBM team, GCN  30958) with AZT-33IK 
telescope of Sayan observatory (Mondy)  starting on 2021-10-25  (UT) 
15:16:32.  We obtained 17 images in R-filter. The afterglow   of the GRB 
211023A (Lipunov   et al., GCN  30977;  Kann  et al. GCN 30982; Hu et 
al. GCN 30990) is clearly detected.   Preliminary photometry of the 
afterglow in a stacked image is following

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

2021-10-25 15:16:32  2.10265    R      17*120  19.87 0.15  21.0

The photometry is based on the nearby USNO-B1.0 stars
04:53:23.10336 +85:19:26.4720 14.09
04:52:47.26344 +85:22:52.1508 15.75

Based on photometry reported early (Kann  et al. GCN 30982; Hu et al. 
GCN 30990)  we can approximate a light curve of the afterglow as a power 
law with the index of 1.49+/-0.03. See also the figure of the light curve in
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