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Article: Could electron-positron annihilation lines in the Galactic center result from pulsar winds?

TitleCould electron-positron annihilation lines in the Galactic center result from pulsar winds?
Authors
KeywordsGalaxy: Center
Gamma-Rays: Theory
Pulsars: General
Issue Date2006
PublisherE D P Sciences. The Journal's web site is located at http://www.aanda.org
Citation
Astronomy And Astrophysics, 2006, v. 446 n. 3, p. 943-948 How to Cite?
AbstractObservations of a strong and extended positron-electron annihilation line emission in the Galactic center (GC) region by the Spectrometer on the International Gamma-Ray Astrophysical Laboratory (SPI/INTEGRAL) are challenging to the existing models of positron sources in the Galaxy. In this paper, we study the possibility that pulsar winds in the GC produce the 511 keV line. We propose that three possible scenarios of pulsar winds may exist as the positron sources: normal pulsars, rapidly spinning strongly magnetized neutron stars (magnetars) in gamma-ray burst (GRB) progenitors, a population of millisecond pulsars in the Galactic center. These e± pairs could be trapped in the region by the magnetic field in the Galactic center, and cool through synchrotron radiation and Coulomb interactions with the medium, thereby becoming non-relativistic particles. The cooling timescales are shorter than the diffuse timescale of positrons, so low-energy positrons could annihilate directly with electrons into 511 keV photons or could form positronium before annihilation. We find that normal pulsars cannot be a significant contributor to the positron sources. Although magnetars in the GC could be potential sources of positrons, their birth rate and birth locations may pose some problems for this scenario. We believe that the most likely candidates for positron sources in the GC may be a population of millisecond pulsars in the GC. Our preliminary estimations predict that the e± annihilation rate in the GC is ≥5 × 1042 s-1, which is consistent with the present observational constraints. Therefore, the e± pairs from pulsars winds can contribute significantly to the positron sources in the Galactic center region. Furthermore, since the diffusion length of positrons is short, we predict that the intensity distribution of the annihilation line should follow the distribution of millisecond pulsars, which should then correlate to the mass distribution in the GC. © ESO 2006.
Persistent Identifierhttp://hdl.handle.net/10722/174995
ISSN
2014 Impact Factor: 4.378
2015 SCImago Journal Rankings: 2.446
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorWang, Wen_US
dc.contributor.authorPun, CSJen_US
dc.contributor.authorCheng, KSen_US
dc.date.accessioned2012-11-26T08:48:41Z-
dc.date.available2012-11-26T08:48:41Z-
dc.date.issued2006en_US
dc.identifier.citationAstronomy And Astrophysics, 2006, v. 446 n. 3, p. 943-948en_US
dc.identifier.issn0004-6361en_US
dc.identifier.urihttp://hdl.handle.net/10722/174995-
dc.description.abstractObservations of a strong and extended positron-electron annihilation line emission in the Galactic center (GC) region by the Spectrometer on the International Gamma-Ray Astrophysical Laboratory (SPI/INTEGRAL) are challenging to the existing models of positron sources in the Galaxy. In this paper, we study the possibility that pulsar winds in the GC produce the 511 keV line. We propose that three possible scenarios of pulsar winds may exist as the positron sources: normal pulsars, rapidly spinning strongly magnetized neutron stars (magnetars) in gamma-ray burst (GRB) progenitors, a population of millisecond pulsars in the Galactic center. These e± pairs could be trapped in the region by the magnetic field in the Galactic center, and cool through synchrotron radiation and Coulomb interactions with the medium, thereby becoming non-relativistic particles. The cooling timescales are shorter than the diffuse timescale of positrons, so low-energy positrons could annihilate directly with electrons into 511 keV photons or could form positronium before annihilation. We find that normal pulsars cannot be a significant contributor to the positron sources. Although magnetars in the GC could be potential sources of positrons, their birth rate and birth locations may pose some problems for this scenario. We believe that the most likely candidates for positron sources in the GC may be a population of millisecond pulsars in the GC. Our preliminary estimations predict that the e± annihilation rate in the GC is ≥5 × 1042 s-1, which is consistent with the present observational constraints. Therefore, the e± pairs from pulsars winds can contribute significantly to the positron sources in the Galactic center region. Furthermore, since the diffusion length of positrons is short, we predict that the intensity distribution of the annihilation line should follow the distribution of millisecond pulsars, which should then correlate to the mass distribution in the GC. © ESO 2006.en_US
dc.languageengen_US
dc.publisherE D P Sciences. The Journal's web site is located at http://www.aanda.orgen_US
dc.relation.ispartofAstronomy and Astrophysicsen_US
dc.subjectGalaxy: Centeren_US
dc.subjectGamma-Rays: Theoryen_US
dc.subjectPulsars: Generalen_US
dc.titleCould electron-positron annihilation lines in the Galactic center result from pulsar winds?en_US
dc.typeArticleen_US
dc.identifier.emailPun, CSJ: jcspun@hkucc.hku.hken_US
dc.identifier.emailCheng, KS: hrspksc@hkucc.hku.hken_US
dc.identifier.authorityPun, CSJ=rp00772en_US
dc.identifier.authorityCheng, KS=rp00675en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1051/0004-6361:20053559en_US
dc.identifier.scopuseid_2-s2.0-32044450591en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-32044450591&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume446en_US
dc.identifier.issue3en_US
dc.identifier.spage943en_US
dc.identifier.epage948en_US
dc.identifier.isiWOS:000234801300014-
dc.publisher.placeFranceen_US
dc.identifier.scopusauthoridWang, W=16173884400en_US
dc.identifier.scopusauthoridPun, CSJ=7003931846en_US
dc.identifier.scopusauthoridCheng, KS=9745798500en_US
dc.identifier.citeulike2523336-

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