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Article: A three-dimensional outer magnetospheric gap model for gamma-ray pulsars: Geometry, pair production, emission morphologies, and phase-resolved spectra

TitleA three-dimensional outer magnetospheric gap model for gamma-ray pulsars: Geometry, pair production, emission morphologies, and phase-resolved spectra
Authors
KeywordsGamma rays: theory
Pulsars: general
Stars: magnetic fields
Issue Date2000
PublisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205
Citation
Astrophysical Journal Letters, 2000, v. 537 n. 2 PART 1, p. 964-976 How to Cite?
AbstractA three-dimensional pulsar magnetosphere model is used to study the geometry of outer magnetospheric gap accelerators, following seminal work of Romani and coworkers. The size of the outer gap is self-consistently limited by pair production from collisions of thermal photons from polar cap heating of backflow outer gap current with curvature photons emitted by gap-accelerated charged particles. In principle, there could be two topologically disconnected outer gaps. Conditions for local pair production such as local field line curvature, soft X-ray density, electric field, etc., support pair production inside an outer gap only between r in(φ) (the radius of the null surface at azimuthal angle φ) and r lim(φ) ≈ 6r in(φ = 0) ≪ R L (the light cylinder radius). Secondary pairs, on the other hand, are produced almost everywhere outside the outer gap by collisions between curvature photons and synchrotron X-rays emitted by these secondary pairs. These processes produce a wide X-ray fan beam in the outgoing direction and a very narrow beam in the incoming direction for each outer gap. For pulsars with a large magnetic dipole inclination angle, part of the incoming y-ray beam will be absorbed by the stellar magnetic field. If the surface magnetic field is dominated by a far off-center dipole moment (e.g., as in a proposed "plate tectonic" model), gravitational bending of photons from polar cap accelerators and their ultimate conversion into outflowing e ± pairs can result in the quenching of one of these two outer gaps. Various emission morphologies for the pulsar (depending on magnetic inclination angle and viewing angle) are presented. Double-peak light curves with strong bridges are most common. From the three-dimensional structure of the outer gap and its local properties, we calculate phase-resolved spectra of gamma-ray pulsars and apply them to observed spectra of the Crab pulsar.
Persistent Identifierhttp://hdl.handle.net/10722/43327
ISSN
2015 Impact Factor: 5.487
2015 SCImago Journal Rankings: 3.369
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorCheng, KSen_HK
dc.contributor.authorRuderman, Men_HK
dc.contributor.authorZhang, Len_HK
dc.date.accessioned2007-03-23T04:43:39Z-
dc.date.available2007-03-23T04:43:39Z-
dc.date.issued2000en_HK
dc.identifier.citationAstrophysical Journal Letters, 2000, v. 537 n. 2 PART 1, p. 964-976en_HK
dc.identifier.issn2041-8205en_HK
dc.identifier.urihttp://hdl.handle.net/10722/43327-
dc.description.abstractA three-dimensional pulsar magnetosphere model is used to study the geometry of outer magnetospheric gap accelerators, following seminal work of Romani and coworkers. The size of the outer gap is self-consistently limited by pair production from collisions of thermal photons from polar cap heating of backflow outer gap current with curvature photons emitted by gap-accelerated charged particles. In principle, there could be two topologically disconnected outer gaps. Conditions for local pair production such as local field line curvature, soft X-ray density, electric field, etc., support pair production inside an outer gap only between r in(φ) (the radius of the null surface at azimuthal angle φ) and r lim(φ) ≈ 6r in(φ = 0) ≪ R L (the light cylinder radius). Secondary pairs, on the other hand, are produced almost everywhere outside the outer gap by collisions between curvature photons and synchrotron X-rays emitted by these secondary pairs. These processes produce a wide X-ray fan beam in the outgoing direction and a very narrow beam in the incoming direction for each outer gap. For pulsars with a large magnetic dipole inclination angle, part of the incoming y-ray beam will be absorbed by the stellar magnetic field. If the surface magnetic field is dominated by a far off-center dipole moment (e.g., as in a proposed "plate tectonic" model), gravitational bending of photons from polar cap accelerators and their ultimate conversion into outflowing e ± pairs can result in the quenching of one of these two outer gaps. Various emission morphologies for the pulsar (depending on magnetic inclination angle and viewing angle) are presented. Double-peak light curves with strong bridges are most common. From the three-dimensional structure of the outer gap and its local properties, we calculate phase-resolved spectra of gamma-ray pulsars and apply them to observed spectra of the Crab pulsar.en_HK
dc.format.extent800856 bytes-
dc.format.extent12158 bytes-
dc.format.mimetypeapplication/pdf-
dc.format.mimetypetext/plain-
dc.languageengen_HK
dc.publisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205en_HK
dc.relation.ispartofAstrophysical Journal Lettersen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.rightsThe Astrophysical Journal. Copyright © University of Chicago Press.en_HK
dc.subjectGamma rays: theoryen_HK
dc.subjectPulsars: generalen_HK
dc.subjectStars: magnetic fieldsen_HK
dc.titleA three-dimensional outer magnetospheric gap model for gamma-ray pulsars: Geometry, pair production, emission morphologies, and phase-resolved spectraen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0004-637X&volume=537&issue=pt 1&spage=964&epage=976&date=2000&atitle=A+Three-dimensional+Outer+Magnetospheric+Gap+Model+for+Gamma-Ray+Pulsars:+Geometry,+Pair+Production,+Emission+Morphologies,+and+Phase-resolved+Spectraen_HK
dc.identifier.emailCheng, KS: hrspksc@hkucc.hku.hken_HK
dc.identifier.authorityCheng, KS=rp00675en_HK
dc.description.naturepublished_or_final_versionen_HK
dc.identifier.doi10.1086/309051en_HK
dc.identifier.scopuseid_2-s2.0-0034412503en_HK
dc.identifier.hkuros63942-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-0034412503&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume537en_HK
dc.identifier.issue2 PART 1en_HK
dc.identifier.spage964en_HK
dc.identifier.epage976en_HK
dc.identifier.isiWOS:000088451100039-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridCheng, KS=9745798500en_HK
dc.identifier.scopusauthoridRuderman, M=7006487382en_HK
dc.identifier.scopusauthoridZhang, L=38762428100en_HK

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