[vsnet-grb-info 26051] GRB 200716C: CrAO, Terskol, Assy-Turgen optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28151
SUBJECT: GRB 200716C: CrAO, Terskol, Assy-Turgen optical observations
DATE:    20/07/21 15:34:11 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

A. Pozanenko (IKI), S. Belkin (IKI),  V. Rumyantsev (CrAO), A. Gorshkov 
(INASAN), V. Kim (AFIF, Pulkovo Observatory),  N. Pankov (HSE), K. 
Kamyshnikov (HSE),   M. Krugov (AFIF), A. Volnova (IKI), E. Mazaeva 
(IKI) report on behalf of larger GRB follow-up collaboration:

We observed GRB 200716C (Fermi GBM team, GCN 28123; Ukwatta et al GCN 
28124;  Torii et al., GCN 28139;  Xue et al., GCN 28145; Frederiks et 
al., GCN 28147)  with ZTSH 2.6m telescope of CrAO observatory, 
Zeiss-2000 of Terskol observatory, and AZT-20 telescope of Assy-Turgen 
observatory.   The optical afterglow (Ukwatta et al., GCN 28124; Lipunov 
et al., GCN 28125; Hu et al., GCN 28126; Kumar et al., GCN 28138; 
Gokuldass et al., GCN 28146; Jelinek et al., GCN 28149) and possible 
host galaxy (D’Avanzo et al., GCN 28132)  is detected in a stacked 
image. Preliminary photometry of the (afterglow + possible host galaxy) 
is following

Date       UT start  t-T0    Filter Exp.   OT    Err. UL Telescope
                     (mid, days)     (s)
2020-07-17 19:17:52  0.84735 R      29*60  19.04 0.03 22.0 ZTSh
2020-07-17 19:50:49  0.87023 R      30*60  19.21 0.03 21.9 ZTSh
2020-07-18 18:33:32  1.83323 R      24*120 19.21 0.06 22.1 Zeiss-2000
2020-07-18 19:25:19  1.85253 R      17*60  19.21 0.06 22.1 ZTSh
2020-07-19 17:15:50  2.78066 r'     52*60  19.31 0.03 22.4 AZT-20

The photometry is based for R-calibration on the star
USNO-B1.0_id R
1196-0207871 16.18

and nearby SDSS stars for r' calibration
SDSS-DR12_id        r
J130423.13+294053.3 15.970
J130352.15+293733.9 16.592
J130416.16+293906.8 16.914

The above photometry besides of the first observation   is consistent 
with a brightness of possible host in USNO-B1.0 (R2=19.23) and in SDSS 
DR12 (r'= 19.301 +/- 0.026). We may conclude that we detected afterglow 
only in the first observation on  0.84735 days after trigger at R=19.04 
+/- 0.03.