[AAVSO-HEN] GRB 090418A: optical observation

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  9329
SUBJECT: GRB 090418A: optical observation
DATE:    09/05/09 20:15:43 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

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

We observed the afterglow of  the Swift GRB 090418A (Mangano et al., GCN 
9149) in I-filter on Apr. 20 (UT) 02:34:12 - 04:08:27
and in R-filter on Apr. 20 (UT) 21:03:05 - 22:49:20 with Shajn telescope of 
CrAO. We clearly detect afterglow in both epochs in stacked images. 
Preliminary photometry  of Apr. 20 as well a photometry in V-filter of  Apr. 
18 observations (Pavlenko et al. GCN 9179) is following:

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

0.5476  V       17x60     22.3 +/- 0.2  23.2  1.9"
2.4507  R       70x60     22.8 +/- 0.1  24.4  1.9"

Due to worse seeing (2.4") on Apr. 20 (UT) 02:34:12 - 04:08:27 the afterglow 
is evidently contaminated with nearby galaxy and photometry will be reported 
later. The photometry of Apr. 20 (UT) 21:03:05 - 22:49:20  also should be 
treated with caution due to possible contamination.