TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2452 SUBJECT: IPN/HETE localization of GRB031109 (=H2917; large error box) DATE: 03/11/18 21:09:20 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley and T. Cline, on behalf of the Ulysses, HETE, and Mars Odyssey GRB teams, G. Ricker, J-L Atteia, N. Kawai, D. Lamb, S. Woosley, J. Doty, R. Vanderspek, J. Villasenor, G. Crew, G. Monnelly, 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, I. Mitrofanov, S. Charyshnikov, V. Grinkov, A. Kozyrev, M. Litvak, and A. Sanin, on behalf of the HEND-Odyssey GRB team, and W. Boynton, C. Fellows, K. Harshman, C. Shinohara and R. Starr, on behalf of the GRS/Odyssey GRB team, report: Ulysses, Mars Odyssey-HEND, and HETE (FREGATE and WXM) observed this GRB at 40308 seconds. Its duration was approximately 20 seconds. As the two triangulation annuli (Ulysses/HETE and Ulysses/Odyssey) are practically coincident, the IPN localization can best be expressed as a single annulus centered at RA, Decl(2000)=350.299, -15.584 degrees, whose radius is 42.882 +/- 0.076 degrees. GRB031109 was detected by HETE as trigger H2917. The burst was detected just a few seconds after the start of FREGATE and WXM operations: it is seen as a two-peaked burst with a hard spectrum (Epeak > 300 keV) and a 25-100 keV fluence of 3E-6 erg/cm2. The burst occurred well before the onset of star tracker operations, so the satellite aspect at the time of the trigger is not well known: the HETE localization is a circle of 10 degree radius centered at RA = 21h 35m, dec = 25d 30'. The IPN annulus intersects this circle at four points to form an error box whose area is approximately 7900 sq. arcmin. The intersection points are: RA(2000) DEC(2000) 320.708 15.912 334.747 24.605 320.885 15.865 334.721 24.431 A map has been posted at ssl.berkeley.edu/ipn3/031109. HETE lightcurves and the results of automated spectral analyses can be found on the HETE web page http://space.mit.edu/HETE/Bursts/GRB031109a. This error box may be improved.