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Article: A systematic study of soft X-ray pulse profiles of magnetars in quiescence

TitleA systematic study of soft X-ray pulse profiles of magnetars in quiescence
Authors
Keywordsstars: magnetars
stars: neutron
pulsars: general
X-rays: stars
Issue Date2019
PublisherOxford University press, co-published with Royal Astronomical Society. The Journal's web site is located at http://www.oxfordjournals.org/our_journals/mnras/
Citation
Monthly Notices of the Royal Astronomical Society, 2019, v. 485 n. 3, p. 4274-4286 How to Cite?
AbstractMagnetars are neutron stars with extremely high surface magnetic fields. They show diverse X-ray pulse profiles in the quiescent state. We perform a systematic Fourier analysis of their soft X-ray pulse profiles. We find that most magnetars have a single-peaked profile and hence have low amplitudes of the second Fourier harmonics (A2). On the other hand, the pulsed fraction (PF) spreads over a wide range. We compared the results with theoretical profiles assuming various surface hotspot asymmetries, viewing geometries, and beaming functions. We found that a single value of the intensity ratio r between two antipodal hotspots is unable to reproduce the observed distribution of A2 and PF for all magnetars. The inferred r is probably anticorrelated with the thermal luminosity, implying that high-luminosity magnetars tend to have two symmetric hotspots. Our results are consistent with theoretical predictions, for which the existence of an evolving toroidal magnetic field breaks the symmetry of the surface temperature.
Persistent Identifierhttp://hdl.handle.net/10722/272945
ISSN
2019 Impact Factor: 5.356
2015 SCImago Journal Rankings: 2.806

 

DC FieldValueLanguage
dc.contributor.authorHu, CP-
dc.contributor.authorNg, CY-
dc.contributor.authorHo, WCG-
dc.date.accessioned2019-08-06T09:19:35Z-
dc.date.available2019-08-06T09:19:35Z-
dc.date.issued2019-
dc.identifier.citationMonthly Notices of the Royal Astronomical Society, 2019, v. 485 n. 3, p. 4274-4286-
dc.identifier.issn0035-8711-
dc.identifier.urihttp://hdl.handle.net/10722/272945-
dc.description.abstractMagnetars are neutron stars with extremely high surface magnetic fields. They show diverse X-ray pulse profiles in the quiescent state. We perform a systematic Fourier analysis of their soft X-ray pulse profiles. We find that most magnetars have a single-peaked profile and hence have low amplitudes of the second Fourier harmonics (A2). On the other hand, the pulsed fraction (PF) spreads over a wide range. We compared the results with theoretical profiles assuming various surface hotspot asymmetries, viewing geometries, and beaming functions. We found that a single value of the intensity ratio r between two antipodal hotspots is unable to reproduce the observed distribution of A2 and PF for all magnetars. The inferred r is probably anticorrelated with the thermal luminosity, implying that high-luminosity magnetars tend to have two symmetric hotspots. Our results are consistent with theoretical predictions, for which the existence of an evolving toroidal magnetic field breaks the symmetry of the surface temperature.-
dc.languageeng-
dc.publisherOxford University press, co-published with Royal Astronomical Society. The Journal's web site is located at http://www.oxfordjournals.org/our_journals/mnras/-
dc.relation.ispartofMonthly Notices of the Royal Astronomical Society-
dc.rightsMonthly Notices of the Royal Astronomical Society. Copyright © Oxford University press, co-published with Royal Astronomical Society.-
dc.rightsThis article has been accepted for publication in [Monthly Notices of the Royal Astronomical Society] ©: [2019] [CP Hu, CY Ng and WCG Ho] Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.-
dc.subjectstars: magnetars-
dc.subjectstars: neutron-
dc.subjectpulsars: general-
dc.subjectX-rays: stars-
dc.titleA systematic study of soft X-ray pulse profiles of magnetars in quiescence-
dc.typeArticle-
dc.identifier.emailNg, CY: ncy@bohr.physics.hku.hk-
dc.identifier.authorityNg, CY=rp01706-
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1093/mnras/stz513-
dc.identifier.scopuseid_2-s2.0-85067053739-
dc.identifier.hkuros299910-
dc.identifier.volume485-
dc.identifier.issue3-
dc.identifier.spage4274-
dc.identifier.epage4286-
dc.publisher.placeUnited Kingdom-

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