912 research outputs found
GRB Astrophysics in the Swift Era and Beyond
Gamma-ray Bursts (GRBs) are relativistic cosmological beacons of transient
high energy radiation whose afterglows span the electromagnetic spectrum.
Theoretical expectations of correlated neutrino emission position GRBs at an
astrophysical nexus for a metamorphosis in our understanding of the Cosmos.
This new dawn in the era of experimental (particle) astrophysics and cosmology
is afforded by current facilities enabling the novel astronomy of high energy
neutrinos, in concert with unprecedented electromagnetic coverage. In that
regard, GRBs represent a compelling scientific theme that may facilitate
fundamental breakthroughs in the context of Swift, Fermi and IceCube.
Scientific synergy will be achieved by leveraging the combined sensitivity of
contemporaneous ground-based and satellite observatories, thus optimizing their
collective discovery potential. Hence, the advent of GRB multi-messenger
astronomy may cement an explicit connection to fundamental physics, via nascent
cosmic windows, throughout the next decade.Comment: 5 pages, 1 figure. Contributed to the Proceedings of the 2nd
Heidelberg Workshop: High-Energy Gamma-rays and Neutrinos from Extra-Galactic
Sources (Max Planck Institute for Nuclear Physics
A New Search Paradigm for Correlated Neutrino Emission from Discrete GRBs using Antarctic Cherenkov Telescopes in the Swift Era
We describe the theoretical modeling and analysis techniques associated with
a preliminary search for correlated neutrino emission from GRB980703a, which
triggered the Burst and Transient Source Experiment (BATSE GRB trigger 6891),
using archived data from the Antarctic Muon and Neutrino Detector Array
(AMANDA-B10). Under the assumption of associated hadronic acceleration, the
expected observed neutrino energy flux is directly derived, based upon
confronting the fireball phenomenology with the discrete set of observed
electromagnetic parameters of GRB980703a, gleaned from ground-based and
satellite observations, for four models, corrected for oscillations. Models 1
and 2, based upon spectral analysis featuring a prompt photon energy fit to the
Band function, utilize an observed spectroscopic redshift, for isotropic and
anisotropic emission geometry, respectively. Model 3 is based upon averaged
burst parameters, assuming isotropic emission. Model 4, based upon a Band fit,
features an estimated redshift from the lag-luminosity relation with isotropic
emission. Consistent with our AMANDA-II analysis of GRB030329, which resulted
in a flux upper limit of ~0.150 GeV/cm^2/s for model 1, we find differences in
excess of an order of magnitude in the response of AMANDA-B10, among the
various models for GRB980703a. Implications for future searches in the era of
Swift and IceCube are discussed.Comment: 7 pages, 4 figures, 4 tables, Contributed to the Proceedings of The
16th Annual Astrophysics Conference in Maryland: Gamma Ray Bursts in the
Swift Era. Edited by Stephen S. Holt, Neil Gehrels and John A. Nousek (2006
Correlative Spectral Analysis of Gamma-Ray Bursts using Swift-BAT and GLAST-GBM
We discuss the preliminary results of spectral analysis simulations involving
anticipated correlated multi-wavelength observations of gamma-ray bursts (GRBs)
using Swift's Burst Alert Telescope (BAT) and the Gamma-Ray Large Area Space
Telescope's (GLAST) Burst Monitor (GLAST-GBM), resulting in joint spectral
fits, including characteristic photon energy (Epeak) values, for a conservative
annual estimate of ~30 GRBs. The addition of BAT's spectral response will (i)
complement in-orbit calibration efforts of GBM's detector response matrices,
(ii) augment GLAST's low energy sensitivity by increasing the ~20-100 keV
effective area, (iii) facilitate ground-based follow-up efforts of GLAST GRBs
by increasing GBM's source localization precision, and (iv) help identify a
subset of non-triggered GRBs discovered via off-line GBM data analysis. Such
multi-wavelength correlative analyses, which have been demonstrated by
successful joint-spectral fits of Swift-BAT GRBs with other higher energy
detectors such as Konus-WIND and Suzaku-WAM, would enable the study of
broad-band spectral and temporal evolution of prompt GRB emission over three
energy decades, thus potentially increasing the science return without placing
additional demands upon mission resources throughout their contemporaneous
orbital tenure over the next decade.Comment: 5 pages. Adapted from a contribution to the Proceedings of the 2008
Nanjing GRB Conference. Edited by Y. F. Huang, Z. G. Dai and B. Zhan
Spectral and temporal analysis of the joint Swift/BAT-Fermi/GBM GRB sample
Using the gamma-ray bursts simultaneously detected by Swift/BAT and Fermi/GBM
we performed a joint spectral and temporal analysis of the prompt emission data
and confirm the rough correlation between the BAT-band photon index Gamma_BAT
and the peak spectral energy Epeak. With the redshift known sub-sample, we
derived the isotropic gamma-ray energy E_gamma,iso and also confirm the
E_gamma,iso - Epeak,rest relation, with a larger scatter than the Amati sample
but consistent with GBM team analyses. We also compare the T_90 values derived
in the GBM band with those derived in the BAT band and find that for long GRBs
the BAT T_90 is usually longer than the GBM T_90, while for short GRBs the
trend reverses. This is consistent with the soft/hard nature of long/short GRBs
and suggests the importance of an energy-dependent temporal analysis of GRBs.Comment: 18 pages, 9 figures, 3 tables, MNRAS accepted, spectral fits updated,
conclusions unchange
Screening High-z GRBs with BAT Prompt Emission Properties
Detecting high-z GRBs is important for constraining the GRB formation rate,
and tracing the history of re-ionization and metallicity of the universe. Based
on the current sample of GRBs detected by Swift with known redshifts, we
investigated the relationship between red-shift, and spectral and temporal
characteristics, using the BAT event-by-event data. We found red-shift trends
for the peak-flux-normalized temporal width T90, the light curve variance, the
peak flux, and the photon index in simple power-law fit to the BAT event data.
We have constructed criteria for screening GRBs with high red-shifts. This will
enable us to provide a much faster alert to the GRB community of possible
high-z bursts.Comment: 4 pages, 4 figures, to be published in the proceedings of ''Gamma Ray
Bursts 2007'', Santa Fe, New Mexico, November 5-
Temporal Profiles and Spectral Lags of XRF 060218
The spectral and temporal properties of the non-thermal emission ofthe nearby
XRF 060218 in 0.3-150 keV band are studied. We show that both the spectral
energy distribution and the light curve properties suggest the same origin of
the non-thermal emission detected by {\em Swift} BAT and XRT. This event has
the longest pulse duration and spectral lag observed to date among the known
GRBs. The pulse structure and its energy dependence are analogous to typical
GRBs. By extrapolating the observed spectral lag to the {\em CGRO/BATSE} bands
we find that the hypothesis that this event complies with the same
luminosity-lag relation with bright GRBs cannot be ruled out at
significance level. These intriguing facts, along with its compliance with the
Amati-relation, indicate that XRF 060218 shares the similar radiation physics
as typical GRBs.Comment: 9 pages in emulateapj format, including 4 figures and 1 table,
accepted for publication in ApJ Letter
A Correlation of Spectral Lag Evolution with Prompt Optical Emission in GRBs?
We report on observations of correlated behavior between the prompt gamma-ray
and optical emission from GRB 080319B, which (i) strongly suggest that they
occurred within the same astrophysical source region and (ii) indicate that
their respective radiation mechanisms were most likely dynamically coupled. Our
preliminary results, based upon a new cross-correlation function (CCF)
methodology for determining the time-resolved spectral lag, are summarized as
follows. First, the evolution in the arrival offset of prompt gamma-ray photon
counts between Swift-BAT 15-25 keV and 50-100 keV energy bands (intrinsic
gamma-ray spectral lag) appears to be anti-correlated with the arrival offset
between prompt 15-350 keV gamma-rays and the optical emission observed by
TORTORA (extrinsic optical/gamma-ray spectral lag), thus effectively
partitioning the burst into two main episodes at ~T+28+/-2 sec. Second, prompt
optical emission is nested within intervals of (a) trivial intrinsic gamma-ray
spectral lag (~T+12+-2 and ~T+50+/-2 sec) with (b) discontinuities in the hard
to soft evolution of the photon index for a power law fit to 15-150 keV
Swift-BAT data (~T+8+/-2 and ~T+48+/-1 sec), both of which coincide with the
rise (~T+10+/-1 sec) and decline (~T+50+/-1 sec) of prompt optical emission.
This potential discovery, robust across heuristic permutations of BAT energy
channels and varying temporal bin resolution, provides the first observational
evidence for an implicit connection between spectral lag and the dynamics of
shocks in the context of canonical fireball phenomenology.Comment: 5 pages. Adapted from a contribution to the Proceedings of the 2008
Nanjing GRB Conference. Edited by Y. F. Huang, Z. G. Dai and B. Zhan
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