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 γ\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 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