//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8734 SUBJECT: GRB 081226B: a short-hard GRB detected by INTEGRAL DATE: 08/12/26 14:24:19 GMT FROM: Sandro Mereghetti at IASF/CNR S.Mereghetti, A.Paizis (IASF-Milano), D.Gotz (CEA-Saclay), M.Turler, V.Beckmann, M. Beck (ISDC, Versoix), and J. Borkowski (CAMK, Torun) on behalf of the IBAS Localization Team report: A short hard GRB consisting of a single peak with duration of about 0.7 s has been detected by IBAS in IBIS/ISGRI data at 12:13:11 UT on December 26th. The refined coordinates (J2000) are: RA = 25.495 [degrees] DEC= -47.439 [degrees] with an uncertainty of 2.5 arcmin (90% c.l.). A preliminary analysis gives a peak flux in the 20-200 keV range of about 3 ph/cmq/s (0.2 s integration time) and a fluence over the same energy range of about 10e-7 erg/cmq. A plot of the light curve will be posted at http://ibas.iasf-milano.inaf.it/IBAS_Results.html This message can be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8740 SUBJECT: GRB 081226B: Swift XRT and UVOT upper limits DATE: 08/12/27 10:02:56 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) and E.A. Hoversten (PSU) report on behalf of the Swift team: Swift observed the field of GRB 081226B (Mereghetti et al. GCN Circ 8734) for 8 ks, beginning 9.6 ks after the INTEGRAL trigger. The XRT data (all in Photon Counting mode) contain no source in the INTEGRAL error circle. A 3-sigma upper limit is 0.001 counts/sec which is 5.6e-14 erg cm^-2 s^-1 for a typical GRB spectrum. Given the absence of an XRT position, the UVOT images were compared to archival images from the Digitized Sky Survey. No candidate afterglow was found in the INTEGRAL error circle. UVOT magnitude 3-sigma upper limits are reported in the following table: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ------------------------------------------------------------- WHITE 9744 22737 1414 > 22.24 v 9621 27619 1940 > 20.48 b 9720 21824 1414 > 21.06 u 9694 16082 352 > 20.34 uvw1 10019 15877 313 > 20.20 uvm2 15472 28224 787 > 20.75 uvw2 10812 23271 932 > 21.27 The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight of E_(B-V) = 0.01 mag. All photometry is on the UVOT photometric system described in Poole et al. (2008, MNRAS, 383, 627). This circular is an official product of the Swift XRT and UVOT teams. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8751 SUBJECT: GRB 081226B: Fermi GBM observation DATE: 08/12/29 15:24:54 GMT FROM: Elisabetta Bissaldi at MPE E. Bissaldi (MPE) and S. McBreen (UCD/MPE) report on behalf of the Fermi GBM Team: "At 12:13:10.71 UT on 26 December 2008, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 081226B (trigger 251986391 / 081226509), which was also detected by INTEGRAL (Mereghetti et al. 2008, GCN 8734) The GBM on-ground location is consistent with the INTEGRAL position. The angle from the Fermi LAT boresight is 22 degrees. The GBM light curve consists of a single pulse with a duration (T90) of about 0.35 s (8-1000 keV). The time-averaged spectrum from T0-0.08 s to T0+0.12 s is well fit by a power law function with an exponential high energy cutoff. The power law index is -0.51 +/- 0.17 and the cutoff energy, parameterized as Epeak, is 530 +/- 110 keV (chi squared 300 for 324 d.o.f.). A Band function fits the spectrum equally well with Epeak = 300 +/- 110 keV, alpha = -0.2 +/- 0.3 and beta = -1.82 +/- 0.23 (chi squared 292 for 323 d.o.f.). The event fluence (8-1000 keV) in this time interval for the power law function with exponential cutoff is (6.1 +/- 0.5)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0-0.01 s in the 8-1000 keV band is 17.7 +/- 1.5 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."