[vsnet-grb-info 16284] GRB 150309A: CrAO optic upper limit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17565
SUBJECT: GRB 150309A: CrAO optic upper limit
DATE:    15/03/11 12:55:33 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

V. Rumyantsev (CrAO), K. Antoniuk, E. Mazaeva (IKI),  A. Pozanenko (IKI) 
report on  behalf of larger GRB follow-up collaboration:

We observed the field of the Swift GRB 150309A (Cummings et al., GCN 
17553) with AZT-11 telescope of CrAO observatory starting on Mar. 09 
(UT) 23:39:47. We took several images in R-filter of 180 s exposure. In 
the enhanced XRT position (Osborne et al., GCN 17555) we do not detect 
any object. An upper limit is following

Date       UT start,  t-t0     Filter   Exp.      UL (3 sigma)
                       (mid, days)        (s)

2015-03-09 23:39:47   0.0468   R        20*180    20.9

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