GCN Circular 2442

XRF031109 (=H2919):  A very long XRF localized by HETE

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

T. Donaghy, C. Graziani, E. Fenimore, M. Galassi, M. Matsuoka, T.
Sakamoto, Y. Shirasaki, M. Suzuki, K. Torii, A. Yoshida, Y. Nakagawa,
R. Satoh, Y. Urata, T. Yamazaki and Y. Yamamoto, on behalf of the
HETE WXM Team;

A. Dullighan, R. Vanderspek, G. Crew, J. Doty, G. Prigozhin, J.
Villasenor, J. G. Jernigan, N. Butler, 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, C. Barraud, and K. Hurley on behalf
of the HETE FREGATE Team;

report:

At 19:28:59 UTC (70138 s UT) on 9 November 2003, the HETE FREGATE 
and WXM instruments detected event H2919, a very long X-ray Flash (XRF).

The burst triggered the WXM in the 2-25 keV energy band.  No prompt
notification was distributed due to the low image S/N of the burst
in the flight analysis.  Initial ground analyses showed the burst to 
be soft, with a duration of ~20s.  Because this burst was detected 
seven minutes before the star cameras had come on line, although the 
WXM data localized the burst to a 15' radius, the original error 
estimate for the celestial coordinates was four degrees.  

Further analysis of the burst data set has revealed that the burst
continued at a low level for at least seven and perhaps 10 minutes:
we estimate t50 to be 310 seconds, t90 to be 480s.  Localization of
the photons detected near the end of the burst, and therefore just
before the beginning of star tracker operations, allows the burst to
be localized to an error circle of 20' radius centered at

   R.A. = 00h 17m 03s.49,  (J2000)
   Dec. =  -7o 08' 41"

An automated fit of a cutoff power-law spectrum has been performed
for H2919.  The fit of the model to the data is posted at

   http://space.mit.edu/HETE/Bursts/GRB031109

The automated fit for the first 52 seconds of the burst gives the 
following values of Epeak and the burst fluence (25-100 keV):

-- Epeak      = 29 keV
-- Fluence    = 1.1e-06 erg/cm^2

NB:  The S/N of the fit decreases significantly for longer 
     integration times.

Also posted at the above website are the following data, in the
formats described by Vanderspek (GCN 2421
Not found
 
 
):

-- Fregate light curve and ascii data tables (energy bands A [7-30 keV],
    B [7-80 keV], and C [30-400 keV])
-- Color-color plot location of H2919 relative to other HETE-localized bursts
-- Signal-to-noise histogram location of H2919 in Fregate Band C
    relative to other HETE-localized bursts

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