16,220 research outputs found
Population synthesis of isolated Neutron Stars with magneto--rotational evolution
We revisit the population synthesis of isolated radio-pulsars incorporating
recent advances on the evolution of the magnetic field and the angle between
the magnetic and rotational axes from new simulations of the magneto-thermal
evolution and magnetosphere models, respectively. An interesting novelty in our
approach is that we do not assume the existence of a death line. We discuss
regions in parameter space that are more consistent with the observational
data. In particular, we find that any broad distribution of birth spin periods
with s can fit the data, and that if the alignment angle is
allowed to vary consistently with the torque model, realistic magnetospheric
models are favoured compared to models with classical magneto-dipolar radiation
losses. Assuming that the initial magnetic field is given by a lognormal
distribution, our optimal model has mean strength with width .
However, there are strong correlations between parameters. This degeneracy in
the parameter space can be broken by an independent estimate of the pulsar
birth rate or by future studies correlating this information with the
population in other observational bands (X-rays and -rays).Comment: 10 pages, 9 figures, submitted and accepted to MNRAS, comments
welcom
A common solution to the cosmic ray anisotropy and gradient problems
Multichannel Cosmic Ray (CR) spectra and the large scale CR anisotropy can
hardly be made compatible in the framework of conventional isotropic and
homogeneous propagation models. These models also have problems explaining the
longitude distribution and the radial emissivity gradient of the -ray
galactic interstellar emission. We argue here that accounting for a well
physically motivated correlation between the CR escape time and the spatially
dependent magnetic turbulence power can naturally solve both problems. Indeed,
by exploiting this correlation we find propagation models that fit a wide set
of CR primary and secondary spectra, and consistently reproduce the CR
anisotropy in the energy range 10^2 - 10^4 \GeV and the -ray
longitude distribution recently measured by Fermi-LAT.Comment: 4 pages, 3 figures. v2: Accepted in Phys. Rev. Let
Global anisotropy of arrival directions of ultra-high-energy cosmic rays: capabilities of space-based detectors
Planned space-based ultra-high-energy cosmic-ray detectors (TUS, JEM-EUSO and
S-EUSO) are best suited for searches of global anisotropies in the distribution
of arrival directions of cosmic-ray particles because they will be able to
observe the full sky with a single instrument. We calculate quantitatively the
strength of anisotropies associated with two models of the origin of the
highest-energy particles: the extragalactic model (sources follow the
distribution of galaxies in the Universe) and the superheavy dark-matter model
(sources follow the distribution of dark matter in the Galactic halo). Based on
the expected exposure of the experiments, we estimate the optimal strategy for
efficient search of these effects.Comment: 19 pages, 7 figures, iopart style. v.2: discussion of the effect of
the cosmic magnetic fields added; other minor changes. Simulated UHECR
skymaps available at http://livni.inr.ac.ru/UHECRskymaps
- …