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Gullon M.,University of Alicante | Miralles J.A.,University of Alicante | Vigano D.,Institute of Space science CSIC IEEC | Pons J.A.,University of Alicante
Monthly Notices of the Royal Astronomical Society

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 P0 ≲ 0.5 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 〈log B0[G]〉 ≈ 13.0-13.2 with width σ(log B0) = 0.6-0.7. 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 γ-rays). © 2014 The Authors. Source

Geppert U.,University of Zielona Gora | Geppert U.,German Aerospace Center | Vigano D.,Institute of Space science CSIC IEEC
Monthly Notices of the Royal Astronomical Society

According to the partially screened gap scenario, an efficient electron-positron pair creation, a general precondition of radio-pulsar activity, relies on the existence of magnetic spots, i.e. local concentrations of strong and small-scale magnetic field structures at the surface of neutron stars. They have a strong impact on the surface temperature, which is potentially observable. Here, we reinforce the idea that such magnetic spots can be formed by extracting magnetic energy from the toroidal field that resides in deep crustal layers, via the Hall drift.We study and discuss the magnetothermal evolution of qualitatively different neutron star models and initial magnetic field configurations that lead to the creation of magnetic spots. We find that magnetic spots can be created on a time-scale of 104 yr with magnetic field strengths ≳5 × 1013 G, provided almost the whole magnetic energy is stored in its toroidal component, and that the conductivity in the inner crust is not too large. The lifetime of the magnetic spots is at least ~one million years, being longer if the initial field permeates both core and crust. © 2014 The Authors. Source

Perna R.,University of Colorado at Boulder | Vigano D.,University of Alicante | Pons J.A.,University of Alicante | Rea N.,Institute of Space science CSIC IEEC
Monthly Notices of the Royal Astronomical Society

Isolated neutron stars (NSs) show a bewildering variety of astrophysical manifestations, presumably shaped by themagnetic field strength and topology at birth. Here, using state-of-the-art calculations of the coupled magnetic and thermal evolution of NSs, we compute the thermal spectra and pulse profiles expected for a variety of initial magnetic field configurations. In particular, we contrast models with purely poloidal magnetic fields to models dominated by a strong internal toroidal component. We find that, while the former displays double-peaked profiles and very low pulsed fractions, in the latter, the anisotropy in the surface temperature produced by the toroidal field often results in a single pulse profile, with pulsed fractions that can exceed the 50-60 per cent level even for perfectly isotropic local emission. We further use our theoretical results to generate simulated 'observed' spectra, and show that blackbody (BB) fits result in inferred radii that can be significantly smaller than the actual NS radius, even as low as ~1-2 km for old NSs with strong internal toroidal fields and a high absorption column density along their line of sight. We compute the size of the inferred BB radius for a few representative magnetic field configurations, NS ages and magnitudes of the column density. Our theoretical results are of direct relevance to the interpretation of X-ray observations of isolated NSs, as well as to the constraints on the equation of state of dense matter through radius measurements. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

Vinyoles N.,Institute of Space science CSIC IEEC | Vogel H.,Max Planck Institute for Physics
Journal of Cosmology and Astroparticle Physics

We study the impact on the Sun of an exotic energy-loss channel caused by plasmon decay into fermionic minicharged particles with charge e and mass mf. We compare solar models with this extra emission to helioseismological and neutrino data, obtaining a bound < 2.2 × 10-14 (95% CL) for mf 25 eV. Our result is comparable to previous limits from the cooling of globular cluster stars, while at the same time it is better understood and takes theoretical and observational errors into account. Source

Serenelli A.,Institute of Space science CSIC IEEC
Nuclear Physics B - Proceedings Supplements

The current status of solar models and neutrino predictions is presented in the context of the most recent measurements of solar neutrino fluxes and the unique possibility that a measurement of CN neutrinos offer to determine solar core abundances. We briefly present possible lessons from such a measurement. © 2013 Elsevier B.V. Source

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