[vsnet-grb-info 17665] GRB 160225A: TSHAO optical afterglow detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19102
SUBJECT: GRB 160225A: TSHAO optical afterglow detection
DATE:    16/02/27 21:44:21 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

E. Mazaeva (IKI), A. Kusakin (Fesenkov Astrophysical Institute), I. Reva 
(Fesenkov Astrophysical Institute), A. Volnova (IKI), A. Pozanenko (IKI) 
report on behalf of larger GRB follow-up collaboration:

We observed the Swift GRB 160225A (Siegel et al., GCN 19075) with 
Zeiss-1000 (West, East) 1-m telescopes of Tien Shan Astronomical 
Observatory. We obtained several images in R filter starting on Feb. 25 
(UT) 14:45:56. In the first images we do not detect any optical source 
(Mazaeva et al., GCN 19078). In combine images we detect afterglow 
(Yoshiiet al., GCN 19080; Kuroda  al., GCN 19081; Wiersema al., GCN 
19082).  Preliminary photometry of combined images is following

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

*2016-02-25 14:45:56   0.07022 R       87*90 20.75    0.16  21.4
  2016-02-25 15:30:59   0.09576 R       77*90 21.36    0.20  21.9
  2016-02-25 17:58:10   0.18146 R       52*90  n/d     n/a   21.7

*) Zeiss-1000 West telescope observations

Photometry is based on SDSS-DR9 nearby stars
SDSS-DR9_id            R(Lupton)
J105614.20+533500.1    15.35
J105714.63+533304.9    14.36
J105658.91+533304.1    15.77