[vsnet-grb-info 16411] GRB 150413A: Khureltogot optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17692
SUBJECT: GRB 150413A: Khureltogot optical observations
DATE:    15/04/13 15:55:04 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

S. Schmalz (AIP), A. Pozanenko (IKI),  N. Tungalag (Research Center of 
Astronomy and Geophysics MAS),   E. Mazaeva (IKI), A. Volnova (IKI), 
I.Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB 
follow-up collaboration:

We observed the field of the GRB 150413A (Markwardt  et al., GCN 17688; 
Serino et al., GCN 17691) with ORI-40 telescope of Khureltogot 
observatory starting on Apr., 13 (UT) 14:08:52, i.e. ~10 minutes after 
burst trigger.   Within   BAT/Swift  error circle  we clearly detect 
fading optical source  (Ivanov et al. GCN 17689, Tyurina et al. GCN 
17690). Preliminary photometry of the source in single images is following

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

2015-04-13  14:08:52   0.0069 none     60  14.7 0.1
2015-04-13  14:39:52   0.0318 none     60  15.6 0.1
2015-04-13  15:11:54   0.0541 none     60  16.3 0.1

Photometry is based on nearby USNO-B1.0 stars, R2 mags.
Observation is continuing.