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Article: Non-thermal emissions from outer magnetospheric accelerators of middle-aged pulsars

TitleNon-thermal emissions from outer magnetospheric accelerators of middle-aged pulsars
Authors
KeywordsPulsars: individual: theory
Radiation mechanisms: non-thermal
Issue Date2009
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, 2009, v. 392 n. 1, p. 400-412 How to Cite?
AbstractWe discuss γ-ray emissions from the outer gap accelerators of middle-aged pulsars for part of the series of our studies. A two-dimensional electrodynamic model is used to solve the distribution of accelerating electric fields with electron and positron pair creation and radiation processes in the magnetic meridional plane. We compute the curvature radiation and the synchrotron radiation by solving the evolution of the Lorentz factor and the pitch angle. The calculated spectra are compared with observed phase-averaged spectra. We also use a three-dimensional geometrical model to discuss the pulse profiles. We argue that the outer gap of middle-aged pulsars occupies the whole region between the last-open field lines and the critical magnetic field lines, which are perpendicular to the rotational axis at the light cylinder. We assume that there is no outer gap accelerator inside the light cylinder between the rotational axis and the critical magnetic field lines. For the Geminga pulsar, we demonstrate that the outward curvature radiation dominates in the spectrum above 10 MeV, while the inward synchrotron radiation dominates below 10 MeV. We find that the computed spectrum is consistent with the observations in X-ray through γ-ray bands. With the pulse morphology of the γ-ray emissions, we argue that the inclination angle and the viewing angle for the Geminga pulsar are α ∼ 50° and ξ ∼ 90°, respectively. We also apply our method to another four middle-aged radio pulsars, whose spin-down power and distance from the Earth expect the possibility of detection of γ-ray emissions from those pulsars by Fermi telescope. Applying the inclination angle and the viewing angle inferred from radio polarization characteristics, the visibility of the γ-ray emissions from the outer gap is discussed. We show that γ-ray emissions from PSRs B0355+54, B1449-64 and B1929+10 will probably be detectable by Fermi telescope. For PSR B0740-28, on the other hand, γ-ray emissions will not be detected because the γ-ray beam from the outer gap will be oriented in a different direction from the viewing angle. © 2008 RAS.
Persistent Identifierhttp://hdl.handle.net/10722/134622
ISSN
2015 Impact Factor: 4.952
2015 SCImago Journal Rankings: 2.806
ISI Accession Number ID
Funding AgencyGrant Number
Theoretical Institute for Advanced Research in Astrophysics (TIARA)
Academia Sinica and National Science Council ExcellenceNSC 96-2752-M-007-002-PAE
Funding Information:

The authors appreciate fruitful discussion with K. S. Cheng, K. Hirotani, K. S. Cheng, S. Shibata and R. Taam. Authors also thank anonymous referee for his/her insightful comments on the manuscript. This work was supported by the Theoretical Institute for Advanced Research in Astrophysics (TIARA) operated under Academia Sinica and National Science Council Excellence Projects program in Taiwan administered through grant number NSC 96-2752-M-007-002-PAE.

References

 

DC FieldValueLanguage
dc.contributor.authorTakata, Jen_HK
dc.contributor.authorChang, HKen_HK
dc.date.accessioned2011-06-29T06:18:22Z-
dc.date.available2011-06-29T06:18:22Z-
dc.date.issued2009en_HK
dc.identifier.citationMonthly Notices Of The Royal Astronomical Society, 2009, v. 392 n. 1, p. 400-412en_HK
dc.identifier.issn0035-8711en_HK
dc.identifier.urihttp://hdl.handle.net/10722/134622-
dc.description.abstractWe discuss γ-ray emissions from the outer gap accelerators of middle-aged pulsars for part of the series of our studies. A two-dimensional electrodynamic model is used to solve the distribution of accelerating electric fields with electron and positron pair creation and radiation processes in the magnetic meridional plane. We compute the curvature radiation and the synchrotron radiation by solving the evolution of the Lorentz factor and the pitch angle. The calculated spectra are compared with observed phase-averaged spectra. We also use a three-dimensional geometrical model to discuss the pulse profiles. We argue that the outer gap of middle-aged pulsars occupies the whole region between the last-open field lines and the critical magnetic field lines, which are perpendicular to the rotational axis at the light cylinder. We assume that there is no outer gap accelerator inside the light cylinder between the rotational axis and the critical magnetic field lines. For the Geminga pulsar, we demonstrate that the outward curvature radiation dominates in the spectrum above 10 MeV, while the inward synchrotron radiation dominates below 10 MeV. We find that the computed spectrum is consistent with the observations in X-ray through γ-ray bands. With the pulse morphology of the γ-ray emissions, we argue that the inclination angle and the viewing angle for the Geminga pulsar are α ∼ 50° and ξ ∼ 90°, respectively. We also apply our method to another four middle-aged radio pulsars, whose spin-down power and distance from the Earth expect the possibility of detection of γ-ray emissions from those pulsars by Fermi telescope. Applying the inclination angle and the viewing angle inferred from radio polarization characteristics, the visibility of the γ-ray emissions from the outer gap is discussed. We show that γ-ray emissions from PSRs B0355+54, B1449-64 and B1929+10 will probably be detectable by Fermi telescope. For PSR B0740-28, on the other hand, γ-ray emissions will not be detected because the γ-ray beam from the outer gap will be oriented in a different direction from the viewing angle. © 2008 RAS.en_HK
dc.languageeng-
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.subjectPulsars: individual: theoryen_HK
dc.subjectRadiation mechanisms: non-thermalen_HK
dc.titleNon-thermal emissions from outer magnetospheric accelerators of middle-aged pulsarsen_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0035-8711&volume=392&issue=1&spage=400&epage=412&date=2009&atitle=Non-thermal+emissions+from+outer+magnetospheric+accelerators+of+middle-aged+pulsars-
dc.identifier.emailTakata, J: takata@hku.hken_HK
dc.identifier.authorityTakata, J=rp00786en_HK
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1111/j.1365-2966.2008.14067.xen_HK
dc.identifier.scopuseid_2-s2.0-57849160975en_HK
dc.identifier.hkuros170774-
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-57849160975&selection=ref&src=s&origin=recordpageen_HK
dc.identifier.volume392en_HK
dc.identifier.issue1en_HK
dc.identifier.spage400en_HK
dc.identifier.epage412en_HK
dc.identifier.isiWOS:000262302700032-
dc.publisher.placeUnited Kingdomen_HK
dc.identifier.scopusauthoridTakata, J=22735157300en_HK
dc.identifier.scopusauthoridChang, HK=7407523188en_HK
dc.identifier.citeulike3820145-

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