GRB 020903

G. Ricker, J-L Atteia, N. Kawai, D. Lamb, and S. Woosley on behalf of
the HETE Science Team;

R. Vanderspek, J. Doty, J. Villasenor, G. Crew, G. Monnelly, N. Butler,
T. Cline, J.G. Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin,
G. Azzibrouck, J. Braga, R. Manchanda, and G. Pizzichini, on behalf of
the HETE Operations and HETE Optical-SXC Teams;

C. Graziani, Y. Shirasaki, M. Matsuoka, T. Tamagawa, K. Torii,
T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi, T. Tavenner, and
T. Donaghy, on behalf of the HETE WXM Team;

M. Boer, J-F Olive, J-P Dezalay, and K. Hurley on behalf of the HETE
FREGATE Team;

write:


At 10:05:37.96 UTC (36337.96 s UT) on 3 Sep 2002, the HETE WXM and SXC
instruments detected event H2314, an X-ray flash.  The WXM flight
localization was correct but was not set out as a GCN Notice because
events which trigger only the WXM are currently not sent out, in order
not to overwhelm the community with X-ray burst localizations.  Ground
analysis of the WXM data for the burst produced a refined location,
which was reported in a GCN Position Notice at 13:56:24 UT, 231 minutes
after the burst.  The WXM location can be expressed as a 90% confidence
circle that is 16.6 arcminutes in radius and is centered at

RA = 22h 49m 25s, Dec = -20o 53' 59" (J2000).


Ground analysis of the SXC data for the burst produced a
one-dimensional localization, which -- when combined with the WXM
localization -- produced a further refinement in the location.  This
refined location was reported in a GCN Position Notice at 17:00:34 UT,
7 hrs after the burst.  The refined location produced by combining the
SXC and WXM localizations can be expressed as a 90% confidence
quadrilateral that is 4 arcminutes in width and ~31 arcminutes in
length, is centered at


RA = 22h 49m 01s, Dec = -20o 55' 47" (J2000).

and is defined by

RA = 22h 48m 48.00  -20o 39' 36.0"
RA = 22h 48m 33.60  -20o 42' 36.0"
RA = 22h 49m 10.80  -21o 10' 12.0"
RA = 22h 49m 30.00  -21o 10' 48.0"


In the WXM 2-25 keV band, the burst had a duration of ~3.3 seconds.
The WXM localization SNR was ~10.  The SXC localization SNR was ~3.

Further information (including a light curve) for GRB020903 is provided
at the following URL:

http://space.mit.edu/HETE/Bursts/

This message is citable.

The date of the first observations of GRB 020903 on the CTIO 4-m reported in
GCN 1557
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  should have read "September 4.1".

K. Torii (RIKEN) and H. Yamaoka (Kyushu Univ.) report:

 The entire WXM error circle of XRF 020903 (Ricker, et al. GCN 1530
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 )
was observed at RIKEN with the 0.25-m reflector equipped with
unfiltered cooled CCD AP6E. The observation started at 2002 September
3.6479 UT (5.23 hours after the burst trigger) and 20-s exposures were
repeated.

 The first 168 frames, obtained between 3.6479 and 3.6965 UT, have
been stacked and inspected for the variable source (hereafter VS)
found by Soderberg, et al. (GCN 1554
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 ). In our image (4".2/pixel) a
spatially unresolvable source is detected at (R.A., Dec.) =
(22:48:42.37, -20:46:13.0) (J2000). The position is derived by using
12 comparison stars from UCAC1 and the fitting error is 0".3 in both
coordinates. This position is closer to the galaxy G2 (as tabulated in
USNO-A2.0) rather than to the VS.

 We also find that the flux for the spatially unresolved G2+VS was
2.0+/-0.2 mag fainter than the star 1 in the finding chart of
Soderberg et al. (GCN 1554
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 ), which is consistent with the magnitude
difference (G2 - star 1 = +2.17) in GSC-2.2.1 F magnitude. These
results, both astrometrically and photometrically, show that the VS
was much fainter than the galaxy G2 during our observation.

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