TITLE:   GCN CIRCULAR
NUMBER:  11852
SUBJECT: GRB 110328A / Swift J164449.3+573451: Mondy optical observations
DATE:    11/03/31 16:37:26 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Pozanenko (IKI),  A. Volnova (SAI MSU),  E. Klunko (ISTP) on behalf of 
larger GRB follow up collaboration report:

We continue observation (Volnova et al. GCN 11837) of the field of GRB 
110328A / Swift J164449.3+573451 (Cummings et al. GCN 11823) with AZT-33IK 
telescope of Sayan observatory (Mondy). Several series of images in R- band 
were taken on March 28 an 29. In the first epoch we clearly detect the 
optical counterpart (Cenko et al. GCN 11827, Leloudas et al. GCN 11830), 
while we do not detect it in the second epoch. The photometry below is based 
on the USNO-A2.0 star 1425-08596694 assuming R=16.6. The first column 
represents the time since first Swift trigger  (Cummings et al. GCN 11823).

T0+         Filter,   Exposure, OT mag.,               UpperLimit (3 sigma)
(mid, d)              (s)

0.08944   R        6420        21.50 +/- 0.11       23.7
1.25258   R          870        n/d                         22.9

Based on the above photometry we tentatively suggest the variability of the 
optical counterpart between the two epochs. However the more precise 
calibration of the field stars are necessary to make a definite conclusion 
about variability.

[GCN OPS NOTE(30apr11): Per author's request, Elunko was changed to Klunko.]