GCN Circular 2566

K. Hurley, on behalf of the HETE GRB Team,

E. Mazets and S. Golenetskii, on behalf of the Konus-Wind GRB team,

G. Ricker, J-L Atteia, N. Kawai, D. Lamb, S. Woosley, J. Doty, R.
Vanderspek, J. Villasenor, G. Crew, A. Dullighan, N. Butler, J.G.
Jernigan, A. Levine, F. Martel, E. Morgan, G. Prigozhin, J. Braga, R.
Manchanda, G.  Pizzichini, Y. Shirasaki, C. Graziani, M. Matsuoka, T.
Tamagawa, K. Torii, T. Sakamoto, A. Yoshida, E. Fenimore, M. Galassi,
T. Tavenner, T.  Donaghy, M. Boer, J-F Olive, and J-P Dezalay, on
behalf of the HETE GRB team, and

T. Cline, on behalf of the HETE and Konus-Wind GRB teams, report:

HETE detected two GRBs on 2004 April 03; the presence of Sco X-1 in the
WXM field-of-view made analyses and reporting of their results somewhat
complicated.  Both events were also detected by Konus-Wind, but by no
other instruments in the IPN.

GRB040403A was detected as trigger #H3143 at 16:55:03 UT (60903 SOD).
It was detected primarily in the Fregate 30-400 keV band.  The absence
of a signal in the 7-40 and 7-80 keV bands indicates that the burst was
detected at the edge of the Fregate FOV; there was no discernable
signal in the WXM.  The WXM flight software looked for a real-time
localization for GRB040403A, but was able only to localize Sco X-1:
this position was distributed to the GCN 27
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  seconds after burst
detection.  After detailed analysis of the WXM data, the localization
was retracted two hours after the initial report.  Due to a software
error, the retraction Notice indicated that the trigger was not a real
GRB;  H3143 is indeed a real GRB, but the position distributed in real
time was not that of the burst.

A combination of triangulation, the Konus ecliptic latitude
response, and HETE Earth-blocking give a large 5-sided error box whose
shape is complex, and whose corners are at:

RA(2000)	Decl(2000)

263		+20.5
282		+33.1
302		+37.4
308		+37.8
304		+25.7

A map has been posted at ssl.berkeley.edu/ipn3/040403A.

As observed by Konus-Wind, this burst had a duration of 98s, a 20-2000
keV fluence of 6E-5 erg/cm2 (or 4E-5 in 30-400 keV range), a 20-2000
keV peak flux ~ 2.6E-6 erg/cm2 s, and an Epeak=340+/-20 keV.

GRB040403B was detected as trigger #H3144 at 23:23:55 UT (84236 SOD).
As observed by FREGATE, it consists of two short (0.5s) spikes
separated by ~0.8s.  The burst is seen most strongly in the 30-400 keV
band with an Epeak well above this range.  GRB040403B therefore
qualifies as a short/hard burst.  The burst was marginally detected by
the WXM; unfortunately, the presence of Sco X-1 in the WXM FOV makes
localization of this burst impossible.  The SXC was not operating at
this time because of the full moon.

Triangulation gives an annulus of location centered at
RA, Decl=127.559, +21.669, whose radius is 70.529 +/- 2.155
degrees (3 sigma).  The WXM field of view limits this annulus
to an error box with the following corners:

RA(2000)  Decl(2000)

188.213    -1.116
191.330   -15.436
199.758   +36.566
212.802   +40.309

A map may be viewed at ssl.berkeley.edu/ipn3/040403B.

As observed by Konus-Wind, this burst had a 20-2000 keV fluence
~  2E-6 erg/cm2, a peak flux ~ 4.5E-6 erg/cm2 s, and an
Epeak=1300+/-1000 keV.

This message can be cited.