1,602 research outputs found
High-Energy Emission from Interacting Supernovae: New Constraints on Cosmic-Ray Acceleration in Dense Circumstellar Environments
Supernovae (SNe) with strong interactions with circumstellar material (CSM)
are promising candidate sources of high-energy neutrinos and gamma rays, and
have been suggested as an important contributor to Galactic cosmic rays beyond
1 PeV. Taking into account the shock dissipation by a fast velocity component
of SN ejecta, we present comprehensive calculations of the non-thermal emission
from SNe powered by shock interactions with a dense wind or CSM. Remarkably, we
consider electromagnetic cascades in the radiation zone and subsequent
attenuation in the pre-shock CSM. A new time-dependent phenomenological
prescription provided by this work enables us to calculate gamma-ray, hard
X-ray, radio, and neutrino signals, which originate from cosmic rays
accelerated by the diffusive shock acceleration mechanism. We apply our results
to SN IIn 2010jl and SN Ib/IIn 2014C, for which the model parameters can be
determined from the multi-wavelength data. For SN 2010jl, the more promising
case, by using the the latest Fermi Large Area Telescope (LAT) Pass 8 data
release, we derive new constraints on the cosmic-ray energy fraction,
<0.05-0.1. We also find that the late-time radio data of these interacting SNe
are consistent with our model. Further multi-messenger and multi-wavelength
observations of nearby interacting SNe should give us new insights into the
diffusive shock acceleration in dense environments as well as pre-SN mass-loss
mechanisms.Comment: 16 pages, 10 figures, 3 tables, accepted for publication in ApJ.
Results and conclusions unchange
High Energy neutrino signals from the Epoch of Reionization
We perform a new estimate of the high energy neutrinos expected from GRBs
associated with the first generation of stars in light of new models and
constraints on the epoch of reionization and a more detailed evaluation of the
neutrino emission yields. We also compare the diffuse high energy neutrino
background from Population III stars with the one from "ordinary stars"
(Population II), as estimated consistently within the same cosmological and
astrophysical assumptions. In disagreement with previous literature, we find
that high energy neutrinos from Population III stars will not be observable
with current or near future neutrino telescopes, falling below both IceCube
sensitivity and atmospheric neutrino background under the most extreme
assumptions for the GRB rate. This rules them out as a viable diagnostic tool
for these still elusive metal-free stars.Comment: 9 pages, 5 figures
Liquefaction Analysis of Sand Deposits Based on Cyclic Elasto-Piasticity
The one-dimentional liquefaction analysis of sand deposits is performed by using the theory of two-phase mixture and the elasto-plastic constitutive equations of sand that can describe the dynamic dilatancy effect of soil under cyclic loading. The analytical results obtained by finite difference method explain well the dynamic behavior of sand deposits including liquefaction phenomena. Especially, the stress path which is particular to liquefaction is presented by considering a horizontally confined condition
Very-High-Energy Gamma-Ray Signal from Nuclear Photodisintegration as a Probe of Extragalactic Sources of Ultrahigh-Energy Nuclei
It is crucial to identify the ultrahigh-energy cosmic-ray (UHECR) sources and
probe their unknown properties. Recent results from the Pierre Auger
Observatory favor a heavy nuclear composition for the UHECRs. Under the
requirement that heavy nuclei survive in these sources, using gamma-ray bursts
as an example, we predict a diagnostic gamma-ray signal, unique to nuclei - the
emission of de-excitation gamma rays following photodisintegration. These gamma
rays, boosted from MeV to TeV-PeV energies, may be detectable by gamma-ray
telescopes such as VERITAS, HESS, and MAGIC, and especially the next-generation
CTA and AGIS. They are a promising messenger to identify and study individual
UHE nuclei accelerators.Comment: 7 pages, 4 figures, accepted for publication in PRD, with extended
descriptions. Conclusions unchange
Heterotopic heart transplantation in the rat receiving FK-506 alone or with cyclosporine.
In rats, FK significantly prolonged heterotopic heart graft survival over a wide dose range when given for 2 weeks starting on the day of the operation. Brief courses of FK for one to four days preoperatively, and especially beginning four days postoperatively, allowed long subsequent survival of heart grafts in otherwise untreated recipients. The seeming acceptance of the grafts with postoperative FK treatment was largely but not exclusively donor specific when tested eight days after the last FK dose by second grafts from the same donor v third-party donor grafts. FK in minimally therapeutic doses was synergistic with suboptimal doses of CyA
Weighted Radon transforms for which the Chang approximate inversion formula is precise
We describe all weighted Radon transforms on the plane for which the Chang
approximate inversion formula is precise. Some subsequent results, including
the Cormack type inversion for these transforms, are also given
Pressure Raman effects and internal stress in network glasses
Raman scattering from binary GexSe1-x glasses under hydrostatic pressure
shows onset of a steady increase in the frequency of modes of corner-sharing
GeSe4 tetrahedral units when the external pressure P exceeds a threshold value
Pc. The threshold pressure Pc(x) decreases with x in the 0.15 < x < 0.20 range,
nearly vanishes in the 0.20 < x < 0.25 range, and then increases in the 0.25 <
x < 1/3 range. These Pc(x) trends closely track those in the non-reversing
enthalpy, DHnr(x), near glass transitions (Tgs), and in particular, both
DHnr(x) and Pc(x) vanish in the reversibility window (0.20 < x < 0.25). It is
suggested that Pc provides a measure of stress at the Raman active units; and
its vanishing in the reversibility window suggests that these units are part of
an isostatically rigid backbone. Isostaticity also accounts for the non-aging
behavior of glasses observed in the reversibility window
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