[vsnet-grb-info 17271] GRB 151027A: Maidanak optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18635
SUBJECT: GRB 151027A: Maidanak optical observations
DATE:    15/11/22 21:48:09 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

A. Pozanenko (IKI), E. Mazaeva (IKI), A. Volnova (IKI),  O. Burhonov 
(UBAI) report on behalf of larger GRB follow-up collaboration:

We observed the Swift GRB 151027A  (Maselli  et al., GCN 18478)  with 
AZT-22 telescope of Maidanak observatory equipped with SNUCAM in R 
filter. We obtained several images in R-filter on Oct., 30, Nov., 6 and 
  Nov., 9 under mean FWHM of about 0.9".  The afterglow (Maselli et al., 
GCN 18478; Zheng and  Filippenko, GCN 18479) is clearly detected in each 
epoch.  The afterglow is well separated from nearby source  (Dichiara et 
al.GCN 18510; Mazaeva et al., GCN 18559).

Preliminary photometry of the afterglow  is following

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

2015-11-06   15:04:07  10.474   R        10*300   23.30   0.24
2015-11-09   14:06:04  13.443   R        10*300   23.33   0.20

The photometry is based on nearby USNO-B1.0 stars

USNO-B.1_id  R2
1513-0237223 16.66
1513-0237251 16.81
1513-0237270 16.78

A preliminary light curve of the afterglow can be found in 
http://grb.rssi.ru/GRB151027A/GRB151027A_lc.png

At this time it is unclear what is a reason of flattening of the light 
curve at 11-13 days. It might be SN signature or it is continuing bumps 
of the light curve previously seen at least on ~ 1.3 days and ~3 days.