TITLE:   GCN CIRCULAR
NUMBER:  17815
SUBJECT: GRB 150512A: CrAO optical observations
DATE:    15/05/14 19:30:18 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

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

We observed the two OT candidates (Singer et al., GCN 17809)  of the 
Fermi GRB  150512A (Zhang et al., GCN 17811) with ZTSh telescope of CrAO 
observatory starting on May. 13 (UT) 21:04:53. Both candidats are 
clearly visible in our images. Photometry of the candidates is following

iPTF15asn:
Date       UT start   t-T0     Filter   Exp.    Source    Err.
                       (mid, days)       (s)
2015-05-13 21:04:53   1.45795  R        16*120  19.20     0.03


iPTF15asm:
Date       UT start   t-T0     Filter   Exp.    Source    Err.
                       (mid, days)       (s)
2015-05-13 21:46:49   1.48417  R        12*120  19.40     0.02

Photometry of iPTF15asm might be biased by nearby galaxy SDSS 
J134044.09+631954.4. However both sources do not fade in comparison with 
early observations (Singer et al., GCN 17809) and most probably cannot 
be considered as afterglow.

Photometry is in Vega, and based on following SDSS stars

SDSS9_id               R_Lupton
J135741.63+650759.8    16.82
J135738.44+650852.4    18.03
J135752.58+650922.2    18.14