GRB 160829A
GCN Circular 19879
Subject
GRB 160829A: Fermi-LAT detection of a short GRB
Date
2016-08-29T17:28:47Z (9 years ago)
From
Judith Racusin at GSFC <judith.racusin@nasa.gov>
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.
GCN Circular 19880
Subject
GRB 160829A: Swift ToO observations
Date
2016-08-29T18:08:18Z (9 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
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.
GCN Circular 19882
Subject
GRB 160829A: Fermi GBM Detection
Date
2016-08-29T23:09:05Z (9 years ago)
From
Rachel Hamburg at UAH <rkh0007@uah.edu>
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."
GCN Circular 19883
Subject
GRB 160829A: Swift-XRT observations
Date
2016-08-30T09:16:42Z (9 years ago)
From
Andy Beardmore at U Leicester <ab271@leicester.ac.uk>
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.