[vsnet-grb-info 7758] GRB 090426: optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9312
SUBJECT: GRB 090426: optical observations
DATE:    09/04/30 23:36:12 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

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

We observed the afterglow (Cummings et al. GCN 9254, Xin et al., GCN  9255) 
of  the Swift GRB 090426 (Swift trigger 350479, Cummings et al. GCN 9254) in 
R and B filters on Apr. 26  between (UT) 18:03:06 -- 19:47:38 with AZT-11 
telescope of CrAO.  We  detect the afterglow in  stacked image in R. 
Astrometry of the afterglow is RA(J2000):  12 36 18.10 Dec(J2000): +32 59 
08.77  with uncertainty of 0.5 arcsec is  compatible with reported in GCN 
9265 (Oates et al).

Preliminary photometry of combined images is based on  USNO-B1.0 
1230-0248707  star  RA=12:36:18.03 Dec=+33:00:02.2   is  following:

T0+     Filter, Exposure, mag.,     err.
(d)             (s)

0.2342  R 15x180   21.3 +/-0.2


The combined image can de found at
http://grb.rssi.ru/GRB090426/GRB090426_AZT-11_R.gif

Taking together early observations (Yoshida et al, GCN 9266, Kinugasa et al, 
GCN 9292, Mao et al, GCN 9285) with our photometry we estimate power law 
decay index as ~0.9 which is compatible with decay index estimated by 
Olivares et al (GCN 9268).