GRB010326a

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 1014
SUBJECT: GRB010326: Localization by HETE
DATE: 01/03/26 07:24:42 GMT
FROM: George Ricker at MIT

G. Ricker, D. Lamb, and S. Woosley on behalf of the HETE Science Team;

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

N. Kawai, M. Matsuoka, Y. Shirasaki, T. Tamagawa, A. Yoshida, E. Fenimore, M. Galassi, and C. Graziani, on behalf of the HETE WXM Team;

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

write:

On 26 March 2001 at 03:15:00 UTC, a hard spectrum, high energy transient at high galactic latitude was detected and localized by HETE. Both the FREGATE and the WXM instruments detected the event. The burst was triggered by FREGATE in 30-400 keV band.

The preliminary coordinates of the burst are R.A. = 11h50m59.11s, Dec. = -23o32'44" (J2000), derived from combining data from the WXM and Boresighted Optical Cameras. The statistical error radius in the WXM localization is 10 arcmin (90% confidence). In addition, we estimate a systematic error radius at present of 10 arcmin about this location. The spacecraft aspect was known to an accuracy of +/- 2 arcmin (95% confidence) from the optical cameras, and will be improved.

The burst exhibited a multiple-peaked structure and lasted about 25 seconds. The peak flux seen with FREGATE (6-30 keV) was roughly 1 Crab. The peak flux was significantly less in the WXM.


TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 1030
SUBJECT: REVISED LOCATION OF GRB010326A
DATE: 01/03/29 21:27:34 GMT
FROM: Kevin Hurley at UCBerkeley/SSL

K. Hurley, on behalf of the Ulysses GRB and HETE teams; T. Cline, on behalf of the Ulysses, Konus-Wind, and HETE GRB teams; E. Mazets and S. Golenetskii, on behalf of the Konus-Wind and Konus-A GRB teams; and G. Ricker, D. Lamb, C. Graziani, E. Fenimore, N. Kawai, and J.-L. Atteia, on behalf of the HETE team report:

Ulysses, Konus-Wind and Konus-A observed GRB010326A. This burst had a duration of ~25 s, a 17 keV - 2.5 MeV fluence of ~4x10^-5 erg/cm2, and a peak flux over 0.25 s of ~8x10^-6 erg/cm2 s. From a cross-correlation of the Ulysses and Konus-Wind time histories, we have triangulated the location of the burst to an annulus centered at RA(2000)=178.727 deg., Decl(2000)=30.803 deg., and radius 81.702+/- 0.028 deg. (3 sigma confidence). The triangulation based on the Konus-Wind and the Konus-A data resulted in an annulus centered at RA(2000)=94.662 deg., Decl(2000)=21.978 deg., and radius 69.7+/- 0.4 deg. (1 sigma confidence). Combining these data, we are able to restrict the location of the burst to the following ~180 square arcmin. error box.

	 RA(2000)       DEC(2000)
	132.9630 o     -38.3005 o (CENTER)
	132.3408 o     -38.5784 o (CORNER)
	132.3988 o     -38.5441 o (CORNER)
	131.5271 o     -38.0568 o (CORNER)
	131.5851 o     -38.0230 o (CORNER)

This location is consistent with the spectra and time history seen in the four HETE FREGATE detectors. The above error box can be refined by further processing.

On this basis, we have concluded that the WXM location reported in GCN 1014 for this burst is spurious. This burst is distinct from the other GRBs (GRB010326B, GCN 1018; GRB010213, GCN 934) for which HETE WXM locations have been reported, in that it has a very low signal-to-noise excess count rate in the WXM, and our further analysis suggests that it is this fact that accounts for the spurious location. The HETE team apologizes for any inconvenience arising from the spurious location.

Acronyms:
HETE=High Energy Transient Explorer
FREGATE=French Gamma Ray Telescope
WXM=Wide Field X-ray Monitor
SXC=Soft X-ray Camera


The Fregate light curve for GRB010326a


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Last modified: March 26, 2001

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