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GCN Circular 3402

Subject
GRB050509c (=H3751): An X-Ray Flash Localized By HETE
Date
2005-05-10T03:51:45Z (19 years ago)
From
Don Lamb at U.Chicago <lamb@oddjob.uchicago.edu>
GRB050509c (=H3751): An X-Ray Flash Localized By HETE

G. Prigozhin, 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. Maetou, 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, 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 050509c at 
22:45:54 UT (81953.95 SOD) on 9 May 2005.  This was a weak burst
consisting of a single pulse ~25 s long, with almost no emission above
18 keV in the WXM.

The WXM flight localization can be expressed as a circle of radius 14
arcminutes (90% confidence) that is centered at 

WXM-Flight:  RA = 12h 52m 39s, Dec =-44d 17' 50" (J2000).  

The first flight localization was distributed in a GCN Notice issued
at 22:46:13 UT, 19 s after the burst trigger.

Ground analysis of the WXM data produced a refined WXM localization
that was in a GCN Notice issued 10 May 05 at 00:43:29 UT.  This ground
WXM localization can be expressed as a rectangle with corners:

 R.A. = 12 52 15.4 ; Dec. = -44 23 06
 R.A. = 12 54 05.0 ; Dec. = -44 23 46
 R.A. = 12 54 01.7 ; Dec. = -45 10 01
 R.A. = 12 52 11.3 ; Dec. = -45 09 18 (J2000).

The burst was also detected by the SXC Y camera.  Ground analysis of
the SXC data produced a long thin rectangle.  Truncating the rectangle 
by the WXM ground localization results in a rectangle with corners:

 R.A. = 12 54 02.9 ; Dec. = -44 52 23
 R.A. = 12 52 12.7 ; Dec. = -44 51 43
 R.A. = 12 52 13.2 ; Dec. = -44 48 43
 R.A. = 12 54 03.1 ; Dec. = -44 49 23 (J2000).

A preliminary spectral analysis indicates that Epk < 19 keV.  The
preliminary fluences are: S(2-30 keV) = 6E-07 erg cm^-2,
S(30-400) = 3E-07 erg cm^-2.  Therefore GRB 050509c is an X-ray flash.

A light curve, skymap, and spectral information for GRB 050509c are
provided at the following URL:

http://space.mit.edu/HETE/Bursts/GRB050509C/
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