GCN Circular 8993

Markku Nissinen (Varkaus, Finland) reports to the AAVSO High Energy Network
the following optical observations of GRB 090313 (Chornock, Li, and
Filippenko, GCN #8979; Mao et al., GCN #8980):

Markku Nissinen reports the detection of the optical counterpart of GRB
090313 using the GRAS-04 telescope sited in Mayhill, NM, USA.  A number
of unfiltered observations with varying exposure times were made using
the 0.25-meter telescope with an SBIG ST8XE CCD camera; observations began
approximately 1 hour post burst.  The afterglow was detected in all frames
with astrometric positions matching those given by Chornock, Li, and
Filippenko (GCN #8979) and Updike et al (GCN #8983) to within positional
errors.

The following unfiltered magnitudes were obtained from the observations
using USNO-A2.0 U0975_07146255 (R magnitude = 15.9) as the comparison:

   obs midpoint(UT)   exptime  mag(CR)   mag.err

2009-03-13 10:14:41  360 sec  16.5  +/-  0.3  (3 x 120 sec)
2009-03-13 10:27:59  300 sec  16.7  +/-  0.3
2009-03-13 10:39:53  600 sec  16.9  +/-  0.3

A FITS image of the 300-second observation is available at the following URL:
ftp://ftp.aavso.org/grb/MarkkuNissinen_GRB090313_2454904.28608_.fits

The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.