//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19879 SUBJECT: GRB 160829A: Fermi-LAT detection of a short GRB DATE: 16/08/29 17:28:47 GMT FROM: Judith Racusin at GSFC J. L. Racusin (NASA/GSFC), G. Vianello (Stanford), D. Kocevski (NASA/GSFC), E. Bissaldi (Politecnico & INFN Bari), and R. Desiante (INFN Torino) report on behalf of the Fermi-LAT team: At 08:01:37 on August 29, 2016 Fermi-LAT detected high-energy emission from GRB 160829A, which was also detected by Fermi-GBM (trigger 494150501/160829334). The best LAT on-ground location is found to be RA, Dec = 201.7, -56.77 (degrees, J2000) with an error radius of 0.12 deg (90% containment, statistical error only). This was 11 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show an increase in the event rate within 10 deg of the GBM location after the GBM trigger that is spatially and temporally correlated with the GBM emission. The highest-energy photon is a 9.5 GeV event which is observed ~2 seconds after the GBM trigger, and the GRB is otherwise relatively faint, with only 3 photons (>100 MeV) with a >90% probability of being associated with the burst. A Swift ToO has been requested for this burst. The Fermi-LAT point of contact for this burst is Judith Racusin (judith.racusin@nasa.gov). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19880 SUBJECT: GRB 160829A: Swift ToO observations DATE: 16/08/29 18:08:18 GMT FROM: Phil Evans at U of Leicester P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the Fermi/LAT GRB 160829A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/ToO_GRBs/00020687 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the Fermi/LAT event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19882 SUBJECT: GRB 160829A: Fermi GBM Detection DATE: 16/08/29 23:09:05 GMT FROM: Rachel Hamburg at UAH R. Hamburg (UAH), C. Meegan (UAH), and O. Roberts (UCD) report on behalf of the Fermi GBM Team: "At 08:01:37.64 UT on 29 August 2016, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 160829 (trigger 494150501 / 160829334), which was also detected by the LAT (Racusin et al. 2016, GCN 19879). The GBM light curve consists of two short peaks with a duration (T90) of about 0.5 s (50-300 keV). The time-averaged spectrum from T0-0.06 s to T0+0.38 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.56 +/- 0.24 and the cutoff energy, parameterized as Epeak, is 771.40 +/- 282.00 keV The event fluence (10-1000 keV) in this time interval is (5.12 +/- 0.49)E-07 erg/cm^2. The 0.064-sec peak photon flux measured starting from T0+0.00 s in the 10-1000 keV band is 5.3 +/- 0.9 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19883 SUBJECT: GRB 160829A: Swift-XRT observations DATE: 16/08/30 09:16:42 GMT FROM: Andy Beardmore at U Leicester A. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 160829A (Racusin et al. GCN Circ. 19879), collecting 4.8 ks of Photon Counting (PC) mode data between T0+37.4 ks and T0+61.4 ks. No X-ray source has been detected within the LAT error region (Racusin et al. GCN Circ. 19879), with a 3 sigma upper limit count rate of 2.6e-3 ct/s (0.3-10keV). An uncatalogued X-ray source was detected 13.3 arcmin from the LAT position at a count rate of (4.9 +/- 1.9)e-3 ct/s. This source is identified by SIMBAD as CD-56 4975 at RA, Dec (J2000) = 13h 28m 03.68s, -56d 54m 30.38s, whose colours are suggestive of a late-type star, which is, therefore, unlikely to be related to the LAT burst. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/ToO_GRBs/00020687. This circular is an official product of the Swift-XRT team.