382 research outputs found
Neutrinos and Gamma Rays from Photomeson Processes in Gamma Ray Bursts
Acceleration of high-energy hadrons in GRB blast waves will be established if
high-energy neutrinos are detected from GRBs. Recent calculations of photomeson
neutrino production are reviewed, and new calculations of high-energy neutrinos
and the accompanying hadronic cascade radiation are presented. If hadrons are
injected in GRB blast waves with an energy corresponding to the measured hard
X-ray/soft gamma-ray emission, then only the most powerful bursts at fluence
levels >~ 3e-4 erg cm^{-2} offer a realistic prospect for detection of muon
neutrinos. Detection of high-energy neutrinos are likely if GRB blast waves
have large baryon loads and Doppler factors <~ 200. Significant limitations on
the hadronic baryon loading and the number of expected neutrinos are imposed by
the fluxes from pair-photon cascades initiated in the same processes that
produce neutrinos.Comment: 4 pages, 2 figures, in 2003 Santa Fe Conference on GRB
On Hadronic Models for the Anomalous -ray Emission Component in GRB 941017
Gonz\'alez et al. (2003) have reported the discovery of an anomalous
radiation component from ~ 1 -- 200 MeV in GRB 941017. This component varies
independently of and contains >~ 3 times the energy found in the prompt ~ 50
keV -- 1 MeV radiation component that is well described by the relativistic
synchrotron-shock model. Acceleration of hadrons to very high energies by GRBs
could give rise to a separate emission component. Two models, both involving
acceleration of ultra-high energy cosmic rays with subsequent photomeson
interactions, are considered. The first involves a pair-photon cascade
initiated by photohadronic processes in the GRB blast wave. Calculations
indicate that the cascade produces a spectrum that is too soft to explain the
observations. A second model is proposed where photopion interactions in the
GRB blast-wave shell give rise to an escaping collimated neutron beam. The
outflowing neutrons undergo further photopion interactions to produce a beam of
hyper-relativistic electrons that can lose most of their energy during a
fraction of a gyroperiod in the Gauss-strength magnetic fields found in the
circumburst medium. This secondary electron beam produces a hard synchrotron
radiation spectrum that could explain the anomalous component in GRB 941017.Comment: 5 pages, 1 figure, in 2003 Santa Fe Conference on GRB
Ultrahigh energy gamma rays: Carriers of cosmological information
Observational data being the basis of contemporary cosmological models are not numerous: Hubble law of redshift for galaxies, element abundances, and observation of cosmic microwave background radiation (MBR). The significance of MBR discovery predicted in the Big-Band model is particularly stressed. Radio astronomical measurements give an information on MBR only near the Earth. Experimental confirmation of evolution of MBR, i.e., its probing in remote epochs, might obviously present a direct verification of the hypothesis of hot expanding Universe. The carriers of similar cosmological information should be particles which, firstly, effectively interact with MBR, and secondly, make it possible to identify unambiguously the epoch of interaction. A possibility to verify a number of cosmological hypotheses by searching the cutoffs in spectra of ultrahigh energy gamma-rays (UHEGR) from extragalactic sources is discussed
Neutral beam model for the anomalous gamma-ray emission component in GRB 941017
Gonz\'alez et al. (2003) have reported the discovery of an anomalous
radiation component from ~ 1 -- 200 MeV in GRB 941017. This component varies
independently of and contains > 3 times the energy found in the prompt ~ 50 keV
-- 1 MeV radiation component that is well described by the relativistic
synchrotron-shock model. Acceleration of hadrons to very high energies can give
rise to two additional emission components, one produced inside the GRB blast
wave and one associated with an escaping beam of ultra-high energy (UHE; >
10^{14} eV) neutrons, gamma rays, and neutrinos. The first component extending
to ~ 100 MeV is from a pair-photon cascade induced by photomeson processes with
the internal synchrotron photons coincident with the prompt radiation. The
outflowing UHE neutral beam can undergo further interactions with external
photons from the backscattered photon field to produce a beam of
hyper-relativistic electrons that lose most of their energy during a fraction
of a gyroperiod in the assumed Gauss-strength magnetic fields of the
circumburst medium. The synchrotron radiation of these electrons has a spectrum
with vF_v index equal to +1 that can explain the anomalous component in GRB
941017. This interpretation of the spectrum of GRB 941017 requires a high
baryon load of the accelerated particles in GRB blast waves. It implies that
most of the radiation associated with the anomalous component is released at >
500 MeV, suitable for observations with GLAST, and with a comparable energy
fluence in ~100 TeV neutrinos that could be detected with a km-scale neutrino
telescope like IceCube.Comment: 4 pages, 1 figure, minor corrections, Astronomy and Astrophysics
Letters, in pres
Extended GeV-TeV Emission around Gamma-Ray Burst Remnants, and the Case of W49B
We investigate the high-energy photon emission around Gamma-Ray Burst (GRB)
remnants caused by ultrahigh-energy cosmic rays (UHECRs) from the GRBs. We
apply the results to the recent report that the supernova remnant W49B is a GRB
remnant in our Galaxy. If this is correct, and if GRBs are sources of UHECRs, a
natural consequence of this identification would be a detectable TeV photon
emission around the GRB remnant. The imaging of the surrounding emission could
provide new constraints on the jet structure of the GRB.Comment: 12 pages, 2 figures, accepted for publication in ApJ
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