X-ray Lightcurves from Realistic Polar Cap Models: Inclined Pulsar Magnetospheres and Multipole Fields
AffiliationUniv Arizona, Dept Phys
Univ Arizona, Dept Astron
Univ Arizona, Steward Observ
pulsars: individual: PSR J0437-4715
MetadataShow full item record
PublisherOXFORD UNIV PRESS
CitationWill Lockhart, Samuel E Gralla, Feryal Özel, Dimitrios Psaltis, X-ray light curves from realistic polar cap models: inclined pulsar magnetospheres and multipole fields, Monthly Notices of the Royal Astronomical Society, Volume 490, Issue 2, December 2019, Pages 1774–1783, https://doi.org/10.1093/mnras/stz2524
RightsCopyright © 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)
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AbstractThermal X-ray emission from rotation-powered pulsars is believed to originate from localized ‘hotspots’ on the stellar surface occurring where large-scale currents from the magnetosphere return to heat the atmosphere. Light-curve modelling has primarily been limited to simple models, such as circular antipodal emitting regions with constant temperature. We calculate more realistic temperature distributions within the polar caps, taking advantage of recent advances in magnetospheric theory, and we consider their effect on the predicted light curves. The emitting regions are non-circular even for a pure dipole magnetic field, and the inclusion of an aligned magnetic quadrupole moment introduces a north–south asymmetry. As the quadrupole moment is increased, one hotspot grows in size before becoming a thin ring surrounding the star. For the pure dipole case, moving to the more realistic model changes the light curves by 5−10percent for millisecond pulsars, helping to quantify the systematic uncertainty present in current dipolar models. Including the quadrupole gives considerable freedom in generating more complex light curves. We explore whether these simple dipole+quadrupole models can account for the qualitative features of the light curve of PSR J0437−4715.
VersionFinal published version
SponsorsNASANational Aeronautics & Space Administration (NASA) [NNX16AC56G]; NSFNational Science Foundation (NSF) [PHY-1752809]