Mon. Not. R. Astron. Soc., 434, 2362-2372 (2013/September-3)
The imprint of the crustal magnetic field on the thermal spectra and pulse profiles of isolated neutron stars.
PERNA R., VIGANO D., PONS J.A. and REA N.
Abstract (from CDS):
Isolated neutron stars (NSs) show a bewildering variety of astrophysical manifestations, presumably shaped by the magnetic 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 50-60percent 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 ∼ 1-2km 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 (2013)
stars: magnetars - stars: magnetic field - stars: neutron
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