2 research outputs found
High energy neutrino early afterglows from gamma-ray bursts revisited
The high energy neutrino emission from gamma-ray bursts (GRBs) has been
expected in various scenarios. In this paper, we study the neutrino emission
from early afterglows of GRBs, especially under the reverse-forward shock model
and late prompt emission model. In the former model, the early afterglow
emission occurs due to dissipation made by an external shock with the
circumburst medium (CBM). In the latter model, internal dissipation such as
internal shocks produces the shallow decay emission in early afterglows. We
also discuss implications of recent Swift observations for neutrino signals in
detail. Future neutrino detectors such as IceCube may detect neutrino signals
from early afterglows, especially under the late prompt emission model, while
the detection would be difficult under the reverse-forward shock model.
Contribution to the neutrino background from the early afterglow emission may
be at most comparable to that from the prompt emission unless the outflow
making the early afterglow emission loads more nonthermal protons, and it may
be important in the very high energies. Neutrino-detections are inviting
because they could provide us with not only information on baryon acceleration
but also one of the clues to the model of early afterglows. Finally, we compare
various predictions for the neutrino background from GRBs, which are testable
by future neutrino-observations.Comment: 18 pages, 12 figures, accepted for publication in PR
High Energy Neutrino Emission and Neutrino Background from Gamma-Ray Bursts in the Internal Shock Model
High energy neutrino emission from GRBs is discussed. In this paper, by using
the simulation kit GEANT4, we calculate proton cooling efficiency including
pion-multiplicity and proton-inelasticity in photomeson production. First, we
estimate the maximum energy of accelerated protons in GRBs. Using the obtained
results, neutrino flux from one burst and a diffuse neutrino background are
evaluated quantitatively. We also take account of cooling processes of pion and
muon, which are crucial for resulting neutrino spectra. We confirm the validity
of analytic approximate treatments on GRB fiducial parameter sets, but also
find that the effects of multiplicity and high-inelasticity can be important on
both proton cooling and resulting spectra in some cases. Finally, assuming that
the GRB rate traces the star formation rate, we obtain a diffuse neutrino
background spectrum from GRBs for specific parameter sets. We introduce the
nonthermal baryon-loading factor, rather than assume that GRBs are main sources
of UHECRs. We find that the obtained neutrino background can be comparable with
the prediction of Waxman & Bahcall, although our ground in estimation is
different from theirs. In this paper, we study on various parameters since
there are many parameters in the model. The detection of high energy neutrinos
from GRBs will be one of the strong evidences that protons are accelerated to
very high energy in GRBs. Furthermore, the observations of a neutrino
background has a possibility not only to test the internal shock model of GRBs
but also to give us information about parameters in the model and whether GRBs
are sources of UHECRs or not.Comment: 14 pages, 17 figures, accepted for publication in PRD, with extended
descriptions. Conclusions unchange