File Download
  Links for fulltext
     (May Require Subscription)
Supplementary

Article: Population study for γ-ray pulsars with the outer-gap model - III. Radiation characteristics and viewing geometry

TitlePopulation study for γ-ray pulsars with the outer-gap model - III. Radiation characteristics and viewing geometry
Authors
KeywordsGamma-rays: stars
Methods: statistical
Pulsars: general
Radiation mechanisms: non-thermal
Stars: neutron
Issue Date2011
PublisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/MNR
Citation
Monthly Notices Of The Royal Astronomical Society, 2011, v. 415 n. 2, p. 1827-1848 How to Cite?
AbstractWe have performed a Monte Carlo simulation of the Galactic population of pulsars and γ-ray observations. We apply a two-layer outer-gap model, which has been developed by Wang, Takata & Cheng, of the γ-ray emission process, and study the radiation characteristics as a function of the magnetic inclination angle (α) and the Earth viewing angle (ζ). In our model, the γ-ray flux and the spectral cut-off energy tend to decrease as the inclination and viewing angles deviate from 90°. The emerging spectrum above 100MeV becomes soft with a photon index p~ 1.8-2 for ζ→ 90○ and p~ 1.2-1.3 for ζ≪ 90°. Our simulation predicts that pulsars with larger inclination angles (α= 70-90°) and larger viewing angles (ζ= 70-90°) have been preferentially detected by the Fermiγ-ray telescope, and hence the observed pulse profiles of the γ-ray pulsars have a double-peak structure rather than a single-peak one. In the simulation, most γ-ray millisecond pulsars are categorized as radio-quiet γ-ray pulsars, because their radio fluxes are under the sensitivities of the major radio surveys. Even if we drastically increase the radio sensitivity by a factor of 10, the number of radio-selected millisecond pulsars detected by Fermi 10-year observations is still much lower than the expected number of γ-ray-selected millisecond pulsars, indicating that radio-quiet millisecond pulsars must contribute to Fermi unidentified sources and/or γ-ray background radiation. We argue that γ-ray pulsars observed with a smaller viewing angle (ζ≪ 90°) will appear as low-efficiency γ-ray pulsars. For example, the unique radiation properties of the low-efficiency γ-ray pulsar PSRJ0659+1414 can be explained by our present gap model with a viewing geometry of α~ζ= 40°-50°. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.
Persistent Identifierhttp://hdl.handle.net/10722/135364
ISSN
2015 Impact Factor: 4.952
2015 SCImago Journal Rankings: 2.806
ISI Accession Number ID
Funding AgencyGrant Number
Hong Kong SAR Government
Funding Information:

We thank A.H. Kong, C.Y. Hui, B. Rudak, Lupin-C.C. Lin, M. Ruderman, R.E. Taam and S. Shibata for useful discussions. We express our appreciation to an anonymous referee for useful comments. We also thank the Theoretical Institute for Advanced Research in Astrophysics (TIARA) operated under the Academia Sinica Institute of Astronomy and Astrophysics, Taiwan, which enabled one author (JT) to use the PC cluster at TIARA. KSC is supported by a 2011 GRF grant of the Hong Kong SAR Government entitled 'Gamma-ray Pulsars'.

References

 

DC FieldValueLanguage
dc.contributor.authorTakata, Jen_HK
dc.contributor.authorWang, Yen_HK
dc.contributor.authorCheng, KSen_HK
dc.date.accessioned2011-07-27T01:34:11Z-
dc.date.available2011-07-27T01:34:11Z-
dc.date.issued2011en_HK
dc.identifier.citationMonthly Notices Of The Royal Astronomical Society, 2011, v. 415 n. 2, p. 1827-1848en_HK
dc.identifier.issn0035-8711en_HK
dc.identifier.urihttp://hdl.handle.net/10722/135364-
dc.description.abstractWe have performed a Monte Carlo simulation of the Galactic population of pulsars and γ-ray observations. We apply a two-layer outer-gap model, which has been developed by Wang, Takata & Cheng, of the γ-ray emission process, and study the radiation characteristics as a function of the magnetic inclination angle (α) and the Earth viewing angle (ζ). In our model, the γ-ray flux and the spectral cut-off energy tend to decrease as the inclination and viewing angles deviate from 90°. The emerging spectrum above 100MeV becomes soft with a photon index p~ 1.8-2 for ζ→ 90○ and p~ 1.2-1.3 for ζ≪ 90°. Our simulation predicts that pulsars with larger inclination angles (α= 70-90°) and larger viewing angles (ζ= 70-90°) have been preferentially detected by the Fermiγ-ray telescope, and hence the observed pulse profiles of the γ-ray pulsars have a double-peak structure rather than a single-peak one. In the simulation, most γ-ray millisecond pulsars are categorized as radio-quiet γ-ray pulsars, because their radio fluxes are under the sensitivities of the major radio surveys. Even if we drastically increase the radio sensitivity by a factor of 10, the number of radio-selected millisecond pulsars detected by Fermi 10-year observations is still much lower than the expected number of γ-ray-selected millisecond pulsars, indicating that radio-quiet millisecond pulsars must contribute to Fermi unidentified sources and/or γ-ray background radiation. We argue that γ-ray pulsars observed with a smaller viewing angle (ζ≪ 90°) will appear as low-efficiency γ-ray pulsars. For example, the unique radiation properties of the low-efficiency γ-ray pulsar PSRJ0659+1414 can be explained by our present gap model with a viewing geometry of α~ζ= 40°-50°. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.en_HK
dc.languageengen_US
dc.publisherBlackwell Publishing Ltd. The Journal's web site is located at http://www.blackwellpublishing.com/journals/MNRen_HK
dc.relation.ispartofMonthly Notices of the Royal Astronomical Societyen_HK
dc.rightsThe definitive version is available at www.blackwell-synergy.com-
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.rights© 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS-
dc.subjectGamma-rays: starsen_HK
dc.subjectMethods: statisticalen_HK
dc.subjectPulsars: generalen_HK
dc.subjectRadiation mechanisms: non-thermalen_HK
dc.subjectStars: neutronen_HK
dc.titlePopulation study for γ-ray pulsars with the outer-gap model - III. Radiation characteristics and viewing geometryen_HK
dc.typeArticleen_HK
dc.identifier.emailTakata, J: takata@hku.hken_HK
dc.identifier.emailCheng, KS: hrspksc@hkucc.hku.hken_HK
dc.identifier.authorityTakata, J=rp00786en_HK
dc.identifier.authorityCheng, KS=rp00675en_HK
dc.description.naturepublished_or_final_version-
dc.identifier.doi10.1111/j.1365-2966.2011.18832.xen_HK
dc.identifier.scopuseid_2-s2.0-79960593598en_HK
dc.identifier.hkuros186460en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-79960593598&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume415en_HK
dc.identifier.issue2en_HK
dc.identifier.spage1827en_HK
dc.identifier.epage1848en_HK
dc.identifier.eissn1365-2966-
dc.identifier.isiWOS:000293756300066-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridTakata, J=22735157300en_HK
dc.identifier.scopusauthoridWang, Y=36085420300en_HK
dc.identifier.scopusauthoridCheng, KS=9745798500en_HK
dc.identifier.citeulike9599629-

Export via OAI-PMH Interface in XML Formats


OR


Export to Other Non-XML Formats