The imprint of the crustal magnetic field on the thermal spectra and pulse profiles of isolated neutron stars

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Title: The imprint of the crustal magnetic field on the thermal spectra and pulse profiles of isolated neutron stars
Authors: Perna, Rosalba | Viganò, Daniele | Pons, José A. | Rea, Nanda
Research Group/s: Astrofísica Relativista
Center, Department or Service: Universidad de Alicante. Departamento de Física Aplicada
Keywords: Stars: magnetars | Stars: magnetic field | Stars: neutron
Knowledge Area: Astronomía y Astrofísica
Issue Date: 24-Jul-2013
Publisher: Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society. 2013, 434(3): 2362-2372. doi:10.1093/mnras/stt1181
Abstract: 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 50–60 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.
Sponsor: This research was supported by NSF grant No. AST 1009396 and NASA grants AR1-12003X, DD1-12053X, GO2-13068X, GO2-13076X (RP), grants AYA 2010-21097-C03-02 (DV, JAP), AYA2009-07391, AYA2012-39303, SGR2009-811, and iLINK 2011-0303 (NR). DV is supported by a fellowship from the Prometeo program for research groups of excellence of the Generalitat Valenciana (Prometeo/2009/103) and NR is supported by a Ramon y Cajal Fellowship.
URI: http://hdl.handle.net/10045/33784
ISSN: 0035-8711 (Print) | 1365-2966 (Online)
DOI: 10.1093/mnras/stt1181
Language: eng
Type: info:eu-repo/semantics/article
Rights: © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
Peer Review: si
Publisher version: http://dx.doi.org/10.1093/mnras/stt1181
Appears in Collections:INV - Astrofísica Relativista - Artículos de Revistas

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