GRB 050807

E.S. Rykoff, W. Rujopakarn, S.A. Yost, F. Yuan (U Mich) report on behalf 
of the ROTSE collaboration:

ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded 
to GRB 050807 (HETE trigger 3889).  The initial response was delayed due 
to confusion with the different coordinates received in the first two 
GCN notices.  Targeted observations of the updated GCN position (trigger 
3889;3) began at 11:09:51.5 UT, 11.1 minutes after the burst, under 
excellent conditions.  We took 10 5-sec, 10 20-sec and 35 60-sec 
exposures.  These unfiltered images are calibrated relative to USNO A2.0.

The final ground error box (trigger 3889;5) is entirely contained within 
the initial targeted observation.  Comparison to the DSS (second epoch) 
reveals no new sources within the 3-sigma error box, for both single 
images and coadding into sets of 10. Individual images have limiting 
magnitudes ranging from 16.3-17.5; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
11:09:51.5   11:12:7.4     136        17.7   666               Y
11:12:16.8   11:16:55.1    284        18.2   812               Y
11:17:9.9    11:28:34.3    684        18.5   1105              Y

M. Maetou, G. Ricker, J-L. Atteia, N. Kawai, D. Lamb, and S. Woosley,
on behalf of the HETE Science Team;
     
M. Arimoto, T. Donaghy, E. Fenimore, M. Galassi, C. Graziani,
J. Kotoku, M. Matsuoka, Y. Nakagawa, T. Sakamoto, R. Sato,
Y. Shirasaki, M. Suzuki, T. Tamagawa, K. Tanaka, Y. Yamamoto,
and A. Yoshida, on behalf of the HETE WXM Team;
     
N. Butler, G. Crew, J. Doty, G. Prigozhin, R. Vanderspek,
J. Villasenor, J. G. Jernigan, A. Levine, G. Azzibrouck, J. Braga,
R. Manchanda, and G. Pizzichini, on behalf of the HETE Operations and
HETE Optical-SXC Teams;
     
M. Boer, J-F Olive, J-P Dezalay, and K. Hurley, on behalf of the HETE
FREGATE Team;
     
report:

The HETE FREGATE, WXM, and SXC instruments detected GRB 050807 
(=H3889) at 10:58:45 UT (39525 SOD) on 7 August 2005.  The correct 
WXM flight localization was first reported in a GCN Notice issued 
at 10:59:19 UT, which was 34s after the burst trigger.

Further WXM and SXC ground localizations were reported in a GCN
Notice issued at 13:47:18 UT.  The final WXM ground localization can
be expressed as an 8 by 48 arcminute box (90% confidence) that is
centered at

WXM-Ground:  RA = 20h 13m 27s, DEC = -36d 57' 06" (J2000)

and defined by the corners:

RA = 20h 13m 16s, DEC = -37d 21' 43"
RA = 20h 12m 40s, DEC = -37d 18' 54"
RA = 20h 13m 38s, DEC = -36d 32' 31"
RA = 20h 14m 14s, DEC = -36d 35' 20".

The SXC localization could only be localized along one axis,
and hence yields a 3 by 32 arcminute box that is centered at

SXC-Ground:  RA = 20h 13m 27s, DEC = -36d 56' 12" (J2000)

and defined by the corners:

RA = 20h 13m 39s, DEC = -36d 40' 23"
RA = 20h 13m 00s, DEC = -37d 11' 20"
RA = 20h 13m 14s, DEC = -37d 12' 18"
RA = 20h 13m 54s, DEC = -36d 40' 52".

The burst has a duration T_90 of ~55 seconds in 6-40 keV and 6-80 keV,
and a T_90 of ~28 seconds in 30-400 keV.  Preliminary spectral analyses
show the 2-30 keV fluence of GRB 050807 to be 1.3 x 10-6 ergs cm-2 and
the 30-400 keV fluence to be 2.2 x 10-6 ergs cm-2.  Thus, GRB 050807 
is classified as an "X-ray-rich" GRB.

A light curve, skymap, and spectral information for GRB 050807 are
provided at the following URL:

http://space.mit.edu/HETE/Bursts/GRB050807

This message may be cited.