//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5684 SUBJECT: IPN triangulation of GRB060928 (long, exceptionally bright) DATE: 06/10/03 00:09:40 GMT FROM: Kevin Hurley at UCBerkeley/SSL K. Hurley and T. Cline, on behalf of the Ulysses and Konus GRB teams, S. Golenetskii, E. Mazets, V. Pal'shin, and D. Frederiks on behalf of the Konus-Wind team, D. M. Smith, R. P. Lin, J. McTiernan, E. Bellm, R. Schwartz, C. Wigger, W. Hajdas, and A. Zehnder, on behalf of the RHESSI GRB team, A. von Kienlin, G. Lichti, and A. Rau, on behalf of the INTEGRAL SPI-ACS GRB team, K.Yamaoka, M.Ohno, Y.Fukazawa, T.Takahashi, M.Tashiro, Y. Terada, T.Murakami, and K.Makishima on behalf of the Suzaku WAM team, and S. Barthelmy, J. Cummings, D. Palmer, N. Gehrels, and H. Krimm, on behalf of the Swift-BAT team, Ulysses, Konus-Wind, RHESSI, INTEGRAL (SPI-ACS), Suzaku (WAM), and Swift (BAT) observed this hard-spectrum GRB starting around 04621 seconds. It had a duration of about 215 s in two distinct episodes, and a fluence of about 3 x 10^-4 erg/cm^2. We have triangulated it to a preliminary ~855 sq. arcmin. error box (3 sigma), whose coordinates are: Center: 127.639, -42.210 Corners: 127.490, -42.705 127.737, -43.008 127.555, -41.399 127.774, -41.726 This error box may be improved. It was outside the Swift BAT field of view for both episodes, and therefore Swift did not image the burst, although it did detect it. However, in the course of a later, preplanned observation beginning at T+10 minutes, BAT imaged a weak source within the IPN error box, at RA, Dec= 127.630, -42.696, which could be the gamma-ray afterglow. A ToO observation of this source has been requested. Further details of the energy spectrum will be given in a forthcoming GCN. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5685 SUBJECT: GRB 060928: RHESSI Spectral Fit DATE: 06/10/03 02:25:07 GMT FROM: Eric Bellm at UCB/SSL E. Bellm, M. Bandstra, S. Boggs, C. Wigger, W. Hajdas, D. M. Smith, and K. Hurley on behalf of the RHESSI team report: As observed by RHESSI, GRB060928 (Hurley et al., GCN 5684) displayed two periods of emission. The first had a duration of ~14s starting at about T0 = 01:17:05 UT. The preliminary fit to the time-integrated RHESSI spectrum from T0 - T0+14s between 500 keV and 10 MeV is simple power law with alpha = -2.21 +0.85/-1.74 (90% confidence levels). The 500 keV-10 MeV fluence is 1.5 E-5 erg/cm^2. The second outburst began at T1 = 01:20:05 UT and had a duration of ~25s. A spectral fit to the time-integrated RHESSI spectrum from T1 - T1+25s between 30 keV and 10 MeV gives a cutoff power law with alpha = -1.36 +0.05/-0.04 E0 = 2090 +480/-370 keV Epeak = 1340 +/- 220 keV The 30 keV-10 MeV fluence is 2.43 +/- 0.91 E-4 erg/cm^2. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5686 SUBJECT: GRB 060928: Swift observations DATE: 06/10/03 21:37:56 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester), J. Cummings (GSFC/UMBC), K. Hurley (UCBerkeley/SSL), D.N. Burrows, D.C. Morris, J.A. Kennea, P. Brown (PSU) and D.M. Palmer (LANL) report on behalf of the Swift team: Swift-BAT serendipitously observed the location of the IPN localised burst GRB 060928 (GCN Circ. 5684, Hurley et al.; GCN Circ. 5685, Bellm et al.), which was out of the BAT field of view when the burst itself happened, during a 28-minute observation beginning 11 minutes after the burst trigger. Ground analysis of BAT data shows a weak source at RA, Dec 127.613, -42.739 (J2000) with a 90% confidence error circle of 2.5 arcmin radius. BAT detects emission for many minutes in the 15-50 keV energy range starting 11 minutes after the original burst and 8 minutes after the larger second burst. This is unusual, and, in fact, such late high energy emission has been seen by BAT only in one previous burst, the extremely energetic very high redshift GRB 050904. Swift-XRT performed a Target of Opportunity observation, starting approximately 5.5 days after the burst. UVOT could not observe the position because of a bright star in the field. Using 7.2 ks of XRT Photon Counting mode data, we detect an uncatalogued source within the IPN error box and close to the weak BAT detection at a position of: RA(J2000) = 08 30 29.90 Dec(J2000) = -42 44 58.5 with an estimated radial uncertainty of 6 arcsec (90% containment, including boresight uncertainties). This is 49 arcsec from the ground-calculated BAT position. The mean count rate of the X-ray source is (4.9 +/- 1.5)e-3 count s^-1 which, assuming a photon index of 2.1 and a Galactic absorbing column of 1.1e22 cm^-2, corresponds to an observed (unabsorbed) flux of 3.5e-13 (8.0e-13) erg cm^-2 s^-1. At the present time it is not possible to determine whether the source is fading. Further observations are needed to verify whether or not this source is, indeed, the afterglow of GRB 060928. This circular is an official product of the Swift team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5688 SUBJECT: GRB 060928: Suzaku/WAM observation of the prompt emission DATE: 06/10/04 16:59:22 GMT FROM: Masanori Ohno at Hiroshima U M. Ohno, T. Takahashi, T. Asano, T. Uehara, Y. Fukazawa (Hiroshima U.), M. Suzuki, Y. Terada, T. Tamagawa (RIKEN), K. Yamaoka, S. Sugita (Aoyama Gakuin U.), M. Tashiro, K. Abe, K. Onda, Y. Sato, M. Suzuki, Y. Urata (Saitama U.), T. Enoto, R. Miyawaki, K. Kokubun, K. Makishima (Univ. of Tokyo), K. Nakazawa, T. Takahashi (ISAS/JAXA), S. Hong (Nihon U.), on behalf of the Suzaku WAM team report: The bright, long burst, GRB 060928 (Hurley et al., GCN 5684), triggered the Suzaku Wideband All-sky Monitor (WAM), which covers the energy range of 50 keV - 5 MeV, at 01:17:01.74 (UT). Two distinct strong bursts were seen in the light curve observed with the WAM. The duration of the first and second burst was about 14 seconds and 70 seconds, respectively. These two bursts were separated by about 200 seconds. Here we report the analysis result only for the first burst. The fluence in 100 - 1000 keV was 2.18(-0.11, +0.11)x10-5 erg/cm2, while the 1-s peak flux was 9.75(-0.47, +0.51) photons/cm2/s in the same energy range. Preliminary result shows that the time-averaged spectrum is well described by a power law with an exponential cutoff as follows. dN/dE ~ E^{-alpha} * exp(-(2-alpha)*E/Epeak) alpha 1.18 (-0.18, +0.17), and Epeak 580 (-70, +112) keV. All the quoted errors are at statistical 90% confidence level, while systematic errors are not included. -- //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5692 SUBJECT: GRB 060928: Correction to GCN 5690 DATE: 06/10/04 22:49:13 GMT FROM: Jean-Luc Atteia at Lab d Astrophys.,OMP,Toulouse The pseudo-redshifts of GRB 060928 given in GCN Circular 5690 have been erroneously computed with the spectral parameters of the 1st peak of this GRB. A computation based on a 15 sec long intervalle near the maximum of the burst gives a smaller pseudo-redshift pz = 1.3 +/- 0.2 We apologize for this mistake. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5721 SUBJECT: GRB 060928: Confirmation of the X-ray afterglow detected by Swift DATE: 06/10/09 07:34:56 GMT FROM: Kim Page at U.of Leicester K.L. Page (U. Leicester) and N. Gehrels (NASA/GSFC) report on behalf of the Swift-XRT team: Swift-XRT performed a second observation of the IPN-discovered burst GRB 060928 on 2006-10-07 starting at 01:17 (9 days after the trigger). In a 10 ks observation, we no longer detect the source reported in GCN Circ. 5686 (Page et al.) Thus, we confirm that this source [previously reported to have a position of RA,Dec 08 30 29.90, -42 44 58.5 (J2000), estimated uncertainty 6 arcsec radius] has faded from view. During this second observation, the 3-sigma upper limit on the count rate is about 3e-3 count s^-1, corresponding to an observed (unabsorbed) flux of 2.1e-13 (4.9e-13) erg cm^-2 s^-1. Since the source has faded over time, it is, indeed, believed to be the X-ray afterglow of GRB 060928. This circular is an official product of the Swift-XRT team.