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On the radiation beaming of bright X-ray pulsars and constraints on neutron star mass-radius relation

Michiel van der Klis; Alexander A Mushtukov; Patrick A Verhagen; Sergey S Tsygankov; Tatiana I Larchenkova; Alexander A Lutovinov

dc.contributor.authorMichiel van der Klis
dc.contributor.authorAlexander A Mushtukov
dc.contributor.authorPatrick A Verhagen
dc.contributor.authorSergey S Tsygankov
dc.contributor.authorTatiana I Larchenkova
dc.contributor.authorAlexander A Lutovinov
dc.date.accessioned2022-10-27T12:09:26Z
dc.date.available2022-10-27T12:09:26Z
dc.identifier.urihttps://www.utupub.fi/handle/10024/156664
dc.description.abstractThe luminosity of accreting magnetized neutron stars can largely exceed the Eddington value due to appearance of accretion columns. The height of the columns can be comparable to the neutron star radius. The columns produce the X-rays detected by the observer directly and illuminate the stellar surface, which reprocesses the X-rays and causes additional component of the observed flux. The geometry of the column and the illuminated part of the surface determine the radiation beaming. Curved space-time affects the angular flux distribution. We construct a simple model of the beam patterns formed by direct and reflected flux from the column. We take into account the possibility of appearance of accretion columns, whose height is comparable to the neutron star radius. We argue that depending on the compactness of the star, the flux from the column can be either strongly amplified due to gravitational lensing, or significantly reduced due to column eclipse by the star. The eclipses of high accretion columns result in specific features in pulse profiles. Their detection can put constraints on the neutron star radius. We speculate that column eclipses are observed in X-ray pulsar V 0332+53, leading us to the conclusion of large neutron star radius in this system (similar to 15 km if M similar to 1.4 M-circle dot). We point out that the beam pattern can be strongly affected by scattering in the accretion channel at high luminosity, which has to be taken into account in the models reproducing the pulse profiles.
dc.language.isoen
dc.publisherOXFORD UNIV PRESS
dc.titleOn the radiation beaming of bright X-ray pulsars and constraints on neutron star mass-radius relation
dc.identifier.urnURN:NBN:fi-fe2021042718849
dc.relation.volume474
dc.contributor.organizationfi=Tuorlan observatorio|en=Tuorla Observatory|
dc.contributor.organization-code2606705
dc.converis.publication-id30084499
dc.converis.urlhttps://research.utu.fi/converis/portal/Publication/30084499
dc.format.pagerange5436
dc.format.pagerange5425
dc.identifier.jour-issn0035-8711
dc.okm.affiliatedauthorTsygankov, Sergey
dc.okm.discipline115 Astronomy and space scienceen_GB
dc.okm.discipline115 Avaruustieteet ja tähtitiedefi_FI
dc.okm.internationalcopublicationinternational co-publication
dc.okm.internationalityInternational publication
dc.okm.typeJournal article
dc.publisher.countryBritanniafi_FI
dc.publisher.countryUnited Kingdomen_GB
dc.publisher.country-codeGB
dc.relation.doi10.1093/mnras/stx2905
dc.relation.ispartofjournalMonthly Notices of the Royal Astronomical Society
dc.relation.issue4
dc.year.issued2018


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