GCN Circular 9324
Subject
GRB 090323: optical observations
Event
Date
2009-05-05T00:46:36Z (17 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Rumyantsev (CrAO), A. Pozanenko (IKI) report on behalf of larger GRB
follow-up collaboration:
We observed the afterglow (Updike et al., GCN 9026; Cenko et al., GCN 9027)
of Fermi GRB 090323 (GBM trigger 259459364 / 090323002; Ohno et al., GCN
9021) on Apr. 28 and Apr. 29 with Shajn telescope of CrAO. We clearly
detect the afterglow in R and do not detect in I- filter. Astrometry of the
afterglow is RA(J2000): 12 42 50.29 Dec(J2000): +17 03 11.98 with
uncertainty of 0.2 arcsec is compatible with reported in GCN 9026.
A photometry of combined images based on USNO-B1.0 star RA=12:42:39.3
Dec=+17:05:05.7 (previously used by Kann et al. GCN 9033) is following:
T0+ Filter, Exposure, mag., err. Seeing
(d) (s)
5.9934 R 91x60 22.7 +/- 0.1 1.6"
6.8990 I 84x60 >22.4 (3sigma) 2.9"
The combined image of the observation on Apr. 28 can be found at
http://grb.rssi.ru/GRB090323/GRB090323_R_ZTSh_090328.gif
Our photometry in R is compatible with estimations obtained in nearby epochs
(Kann et al. GCN 9041, de Ugarte Postigo et al. GCN 9051) and confirms the
flattening of the light curve mentioned by de Ugarte Postigo et al. (GCN
9051). The non-detection of the afterglow in I-filter in second epoch of
our observation (T0+6.899 d) tentatively supports the steepening of light
curve discussed by Kann et al. (GCN 9063). Indeed the upper limit I > 22.4
is translating into R > 22.8 provided the color index R-I ~ 0.4 obtained
from observations of Updike et al. (GCN 9026) and Guidorzi et al. (GCN
9039) is not changing along late time light curve.