261 research outputs found
Stringent Constraint on Galactic Positron Production
The intense 0.511 MeV gamma-ray line emission from the Galactic Center
observed by INTEGRAL requires a large annihilation rate of nonrelativistic
positrons. If these positrons are injected at even mildly relativistic
energies, higher-energy gamma rays will also be produced. We calculate the
gamma-ray spectrum due to inflight annihilation and compare to the observed
diffuse Galactic gamma-ray data. Even in a simplified but conservative
treatment, we find that the positron injection energies must be
MeV, which strongly constrains models for Galactic positron production.Comment: 4 pages, 2 figures; minor revisions, accepted for publication in PR
Neutrino physics from new SNO and KamLAND data and future prospects
We analyze the cumulative data from the latest SNO, KamLAND and other solar
neutrino experiments in the standard scenario of three oscillating active
neutrinos. We determine the solar neutrino oscillation parameters and obtain
new bounds on . We also place constraints on the fraction of
oscillating solar neutrinos that transform to sterile neutrinos with the B
flux normalization left free. Concomitantly, we assess the sensitivity of
future data from the SNO and KamLAND experiments to and to the
sterile neutrino content of the solar flux.Comment: 4 pages, 4 figures. Latest SNO salt-phase data and KamLAND data
included in analyse
Gamma-Ray Constraints on Maximum Cosmogenic Neutrino Fluxes and UHECR Source Evolution Models
The dip model assumes that the ultra-high energy cosmic rays (UHECRs) above
10 eV consist exclusively of protons and is consistent with the spectrum
and composition measure by HiRes. Here we present the range of cosmogenic
neutrino fluxes in the dip-model which are compatible with a recent
determination of the extragalactic very high energy (VHE) gamma-ray diffuse
background derived from 2.5 years of Fermi/LAT data. We show that the largest
fluxes predicted in the dip model would be detectable by IceCube in about 10
years of observation and are within the reach of a few years of observation
with the ARA project. In the incomplete UHECR model in which protons are
assumed to dominate only above 10 eV, the cosmogenic neutrino fluxes
could be a factor of 2 or 3 larger. Any fraction of heavier nuclei in the UHECR
at these energies would reduce the maximum cosmogenic neutrino fluxes. We also
consider here special evolution models in which the UHECR sources are assumed
to have the same evolution of either the star formation rate (SFR), or the
gamma-ray burst (GRB) rate, or the active galactic nuclei (AGN) rate in the
Universe and found that the last two are disfavored (and in the dip model
rejected) by the new VHE gamma-ray background.Comment: 19 pages, 16 figures, JHEP3.cls needed to typese
What is the association of acute renal failure, angiotensin-converting enzyme inhibitor and angiotensin II receptor blocker in a young patient?
Evolution in the Volumetric Type Ia Supernova Rate from the Supernova Legacy Survey
We present a measurement of the volumetric Type Ia supernova (SN Ia) rate
(SNR_Ia) as a function of redshift for the first four years of data from the
Canada-France-Hawaii Telescope (CFHT) Supernova Legacy Survey (SNLS). This
analysis includes 286 spectroscopically confirmed and more than 400 additional
photometrically identified SNe Ia within the redshift range 0.1<z<1.1. The
volumetric SNR_Ia evolution is consistent with a rise to z~1.0 that follows a
power-law of the form (1+z)^alpha, with alpha=2.11+/-0.28. This evolutionary
trend in the SNLS rates is slightly shallower than that of the cosmic
star-formation history over the same redshift range. We combine the SNLS rate
measurements with those from other surveys that complement the SNLS redshift
range, and fit various simple SN Ia delay-time distribution (DTD) models to the
combined data. A simple power-law model for the DTD (i.e., proportional to
t^-beta) yields values from beta=0.98+/-0.05 to beta=1.15+/-0.08 depending on
the parameterization of the cosmic star formation history. A two-component
model, where SNR_Ia is dependent on stellar mass (Mstellar) and star formation
rate (SFR) as SNR_Ia(z)=AxMstellar(z) + BxSFR(z), yields the coefficients
A=1.9+/-0.1 SNe/yr/M_solar and B=3.3+/-0.2 SNe/yr/(M_solar/yr). More general
two-component models also fit the data well, but single Gaussian or exponential
DTDs provide significantly poorer matches. Finally, we split the SNLS sample
into two populations by the light curve width (stretch), and show that the
general behavior in the rates of faster-declining SNe Ia (0.8<s<1.0) is
similar, within our measurement errors, to that of the slower objects
(1.0<s<1.3) out to z~0.8.Comment: Accepted in A
Searching for prompt signatures of nearby core-collapse supernovae by a joint analysis of neutrino and gravitational-wave data
We discuss the science motivations and prospects for a joint analysis of
gravitational-wave (GW) and low-energy neutrino data to search for prompt
signals from nearby supernovae (SNe). Both gravitational-wave and low-energy
neutrinos are expected to be produced in the innermost region of a
core-collapse supernova, and a search for coincident signals would probe the
processes which power a supernova explosion. It is estimated that the current
generation of neutrino and gravitational-wave detectors would be sensitive to
Galactic core-collapse supernovae, and would also be able to detect
electromagnetically dark SNe. A joint GW-neutrino search would enable
improvements to searches by way of lower detection thresholds, larger distance
range, better live-time coverage by a network of GW and neutrino detectors, and
increased significance of candidate detections. A close collaboration between
the GW and neutrino communities for such a search will thus go far toward
realizing a much sought-after astrophysics goal of detecting the next nearby
supernova.Comment: 10 pages, 3 figures. To appear in Class. Quantum Gra
Enhanced Cosmological GRB Rates and Implications for Cosmogenic Neutrinos
Gamma-ray bursts, which are among the most violent events in the universe,
are one of the few viable candidates to produce ultrahigh energy cosmic rays.
Recently, observations have revealed that GRBs generally originate from
metal-poor galaxies and do not directly trace cosmic star formation, as might
have been assumed from their association with core-collapse supernovae. Several
implications follow from these findings. The redshift distribution of observed
GRBs is expected to peak at higher redshift (compared to cosmic star
formation), which is supported by the mean redshift of the Swift GRB sample,
~3. If GRBs are, in fact, the source of the observed UHECR, then cosmic-ray
production would evolve with redshift in a stronger fashion than has been
previously suggested. This necessarily leads, through the GZK process, to an
enhancement in the flux of cosmogenic neutrinos, providing a near-term approach
for testing the gamma-ray burst-cosmic ray connection with ongoing and proposed
UHE neutrino experiments.Comment: 9 pages, 5 figures, references and two appendices added, conclusions
unchanged; accepted for publication in Phys.Rev.
Neutrino Mixing and Nucleosynthesis in Core-Collapse Supernovae
A simple description of core-collapse supernovae is given. Properties of the
neutrino-driven wind, neutrino fluxes and luminosities, reaction rates, and the
equilibrium electron fraction in supernova environments are discussed. Neutrino
mixing and neutrino interactions that are relevant to core-collapse supernovae
are briefly reviewed. The values of electron fraction under several evolution
scenarios that may impact rapid neutron capture process (r-process)
nucleosynthesis are calculated.Comment: 17 pages, 4 figure
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