//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11155 SUBJECT: GRB100826A: Fermi-LAT Observations DATE: 10/08/30 20:52:22 GMT FROM: Julie McEnery at NASA/GSFC Julie McEnery (NASA/GSFC) and Nicola Omodei (Stanford) report on behalf of the Fermi-LAT collaboration. The Fermi Large Area Telescope (LAT) detected emission from GRB 100826A also detected by GBM (trigger 304556304) at 22:58:22.89 on August 26, 2010. The GBM location was at a very large angle of (~70 degrees) to the LAT boresight, and no significant excess is seen using standard analysis procedures. Using a non-standard data selection, over 350 counts above background were detected within a 50 s interval coinciding with the first GBM broad peak. The LAT light curve has a very similar structure to this GBM peak, with the maximum count rate occurring at ~22 s post-trigger. A preliminary study of the instrument performance at such a large inclination suggests that these events are likely to be low energy gamma-rays, with energies less than 200 MeV. This data selection has insufficient spatial resolution to provide a reliable LAT localization. Further analysis is ongoing. The Fermi LAT point of contact for this burst is Julie McEnery (julie.mcenery@nasa.gov). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11156 SUBJECT: IPN triangulation of GRB 100826A DATE: 10/08/30 22:30:23 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley, on behalf of the IPN team, I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin, on behalf of the HEND-Odyssey GRB team, W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr, on behalf of the GRS-Odyssey GRB team, J. Goldsten, on behalf of the MESSENGER GRNS GRB team, S. Golenetskii, R. Aptekar, E. Mazets, V. Pal'shin, D. Frederiks, and T. Cline, on behalf of the Konus-Wind team, V. Connaughton, M. Briggs, and C. Meegan, on behalf of the Fermi GBM team, and K. Yamaoka, M. Ohno, Y. Hanabata, Y. Fukazawa, T. Takahashi, M. Tashiro, Y. Terada, T. Murakami, and K. Makishima, on behalf of the Suzaku WAM team, report: The long, bright GRB 100826A, observed by the Fermi/LAT and Fermi/GBM at 22:58:22.89 UT (McEnery & Omodei, GCN 11155), was also detected by Konus-Wind, Mars Odyssey (HEND), MESSENGER (GRNS), and Suzaku (WAM). We have triangulated it to a preliminary 3 sigma error box whose coordinates are: ----------------------------------------------- RA(2000), deg Dec(2000), deg ----------------------------------------------- Center: 279.593 (18h 38m 22s) -22.128 (-22d 07' 42") Corners: 279.356 (18h 37m 25s) -20.511 (-20d 30' 38") 279.424 (18h 37m 42s) -18.324 (-18d 19' 27") 279.708 (18h 38m 50s) -25.604 (-25d 36' 13") 280.041 (18h 40m 10s) -26.935 (-26d 56' 07") ----------------------------------------------- The error box area is ~1.5 sq. deg This error box may be improved. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11158 SUBJECT: Konus-Wind observation of GRB 100826A DATE: 10/08/31 08:45:39 GMT FROM: Dmitry Frederiks at Ioffe Institute S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin, P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, report: The long bright GRB 100826A (observed by the Fermi/LAT and Fermi/GBM: McEnery & Omodei, GCN 11155; localized by IPN: Hurley et.al, GCN 11156) triggered Konus-Wind at T0=82709.729s UT (22:58:29.729) The burst light curve shows a complex structure with a total duration of ~150 s. The emission is seen up to 10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB100826_T82709/ As observed by Konus-Wind the burst had a fluence of (3.0 +/- 0.25)x10-4 erg/cm2, and a 256-ms peak flux, measured from T0+17.664s, of (1.9 +/- 0.2)x10-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+130.560 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model, for which: the low-energy photon index alpha = -1.31 (-0.05, +0.06), the high energy photon index beta = -2.1 (-0.2, +0.1), the peak energy Ep = 606(-109, +134)keV (chi2 = 85.2/87 dof). The spectrum at the maximum count rate (measured from T0+14.336 to T0+18.432 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model, for which: the low-energy photon index alpha = -0.84 (-0.11, +0.13), the high energy photon index beta = -2.00 (-0.15, +0.10), the peak energy Ep = 536(-97, +134)keV (chi2 = 82.5/79 dof). All the quoted results are preliminary. All the quoted errors are at the 90% confidence level.