[vsnet-grb-info 17904] GRB 160425A MASTER notices: possible host galaxy in the optical error-box

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  19351
SUBJECT: GRB 160425A MASTER notices: possible host galaxy in the optical error-box
DATE:    16/04/26 10:45:15 GMT
FROM:    Vladimir Lipunov at Moscow State U/Krylov Obs  <lipunov at xray.sai.msu.ru>

P.Balanutsa, V. Lipunov, E. Gorbovskoy,   N.Tyurina, V.Kornilov, A.Kuznetsov
Lomonosov Moscow State University, Sternberg Astronomical Institute

D.Buckley, S. Potter, A.Kniazev
South African Astronomical Observatory

MASTER-SAAO telescope  pointed to the unusual short GRB160425A (Krimm et 
al. GCN #19343 ) at 2016-04-25 23:28:59UT 168s after trigger time, 30s first expositions with orthogonal polarimeter filters .
The delay is caused with the short rain, the roof was closed at the trigger time.

MASTER-SAAO auto-detection system discovered OT source at (RA, Dec) = 280.32738,-54.36004
at the first 30s polarized image in 1 tube at  2016-04-25 23:28:59UT with  unfiltered m_OT~18.2+-0.5
(w=0.2B+0.8R calibrated by USNO-B1) http://observ.pereplet.ru/images/MASTERGRB160425A.jpg . 
The second tube in orthogonal polarization filter doesn't see it with 
m_lim=17.7, possibly it depends on polarization of this source.

There is a faint optical source at the Palomar (POSS) both red and blue images. 
But this source doesn't present at USNO-B1 catalogue. There is blue source 
(in  0.411") in GSC2.3.2 with jmag=22.16.
The most probable classification of it is the host galaxy of  short  GRB160425A.

SWIFT UVOT see optical afterglow 19.9m in white filter (150s expos., 
starting 208 seconds after the BAT trigger (23:26:11UT) (Krimm et 
al., GCN Circ. 19343) and  GROND see  afetrglow in g'r'i'z' started at 
04:38 UT on April 26, 2016, 5.2 hrs after the GRB (Bodensteiner et al., 
GCN Circ. 19349).

The analyses will be continued.