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Article: Annihilation emission from the galactic black hole

TitleAnnihilation emission from the galactic black hole
Authors
KeywordsBlack Hole Physics
Cosmic Rays
Galaxy: Center
Gamma Rays: Theory
Radiation Mechanisms: Nonthermal
Issue Date2006
PublisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205
Citation
Astrophysical Journal Letters, 2006, v. 645 n. 2 I, p. 1138-1151 How to Cite?
AbstractBoth diffuse high-energy gamma rays and an extended electron-positron annihilation line emission have been observed in the Galactic Center (GC) region. Although X-ray observations indicate that the Galactic black hole Sgr A* is inactive now, we suggest that Sgr A* can become active when a captured star is tidally disrupted and matter is accreted into the black hole. As a consequence the Galactic black hole could be a powerful source of relativistic protons. We are able to explain the current observed diffuse gamma rays and the very detailed 511 keVannihilation line of secondary positrons by p-p collisions of such protons, with appropriate injection times and energy. Relativistic protons could have been injected into the ambient material if the black hole captured a 50 M ⊙ star at several tens times 10 6 yr ago. An alternative possibility is that the black hole continues to capture stars with ∼1 M ⊙ every 10 5 yr. Secondary positrons produced by p-p collisions at energies ≳30 MeV are cooled down to thermal energies by Coulomb collisions and are annihilated in the warm neutral and ionized phases of the interstellar medium with temperatures about several eV, because the annihilation cross section reaches its maximum at these temperatures. It takes about 10 million years for the positrons to cool down to thermal temperatures so that they can diffuse into a very large extended region around the GC. A much more recent star capture may also be able to account for recent TeV observations within 10 pc of the GC, as well as for the unidentified GeV gamma-ray sources found by EGRET at GC. The spectral difference between the GeV and TeV flux could be explained naturally in this model as well. © 2006. The American Astronomical Society. All rights reserved.
Persistent Identifierhttp://hdl.handle.net/10722/175026
ISSN
2015 Impact Factor: 5.487
2015 SCImago Journal Rankings: 3.369
ISI Accession Number ID
References

 

DC FieldValueLanguage
dc.contributor.authorCheng, KSen_US
dc.contributor.authorChernyshov, DOen_US
dc.contributor.authorDogiel, VAen_US
dc.date.accessioned2012-11-26T08:48:50Z-
dc.date.available2012-11-26T08:48:50Z-
dc.date.issued2006en_US
dc.identifier.citationAstrophysical Journal Letters, 2006, v. 645 n. 2 I, p. 1138-1151en_US
dc.identifier.issn2041-8205en_US
dc.identifier.urihttp://hdl.handle.net/10722/175026-
dc.description.abstractBoth diffuse high-energy gamma rays and an extended electron-positron annihilation line emission have been observed in the Galactic Center (GC) region. Although X-ray observations indicate that the Galactic black hole Sgr A* is inactive now, we suggest that Sgr A* can become active when a captured star is tidally disrupted and matter is accreted into the black hole. As a consequence the Galactic black hole could be a powerful source of relativistic protons. We are able to explain the current observed diffuse gamma rays and the very detailed 511 keVannihilation line of secondary positrons by p-p collisions of such protons, with appropriate injection times and energy. Relativistic protons could have been injected into the ambient material if the black hole captured a 50 M ⊙ star at several tens times 10 6 yr ago. An alternative possibility is that the black hole continues to capture stars with ∼1 M ⊙ every 10 5 yr. Secondary positrons produced by p-p collisions at energies ≳30 MeV are cooled down to thermal energies by Coulomb collisions and are annihilated in the warm neutral and ionized phases of the interstellar medium with temperatures about several eV, because the annihilation cross section reaches its maximum at these temperatures. It takes about 10 million years for the positrons to cool down to thermal temperatures so that they can diffuse into a very large extended region around the GC. A much more recent star capture may also be able to account for recent TeV observations within 10 pc of the GC, as well as for the unidentified GeV gamma-ray sources found by EGRET at GC. The spectral difference between the GeV and TeV flux could be explained naturally in this model as well. © 2006. The American Astronomical Society. All rights reserved.en_US
dc.languageengen_US
dc.publisherInstitute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205en_US
dc.relation.ispartofAstrophysical Journal Lettersen_US
dc.subjectBlack Hole Physicsen_US
dc.subjectCosmic Raysen_US
dc.subjectGalaxy: Centeren_US
dc.subjectGamma Rays: Theoryen_US
dc.subjectRadiation Mechanisms: Nonthermalen_US
dc.titleAnnihilation emission from the galactic black holeen_US
dc.typeArticleen_US
dc.identifier.emailCheng, KS: hrspksc@hkucc.hku.hken_US
dc.identifier.authorityCheng, KS=rp00675en_US
dc.description.naturelink_to_subscribed_fulltexten_US
dc.identifier.doi10.1086/504583en_US
dc.identifier.scopuseid_2-s2.0-33746928399en_US
dc.relation.referenceshttp://www.scopus.com/mlt/select.url?eid=2-s2.0-33746928399&selection=ref&src=s&origin=recordpageen_US
dc.identifier.volume645en_US
dc.identifier.issue2 Ien_US
dc.identifier.spage1138en_US
dc.identifier.epage1151en_US
dc.identifier.isiWOS:000239053900032-
dc.publisher.placeUnited Kingdomen_US
dc.identifier.scopusauthoridCheng, KS=9745798500en_US
dc.identifier.scopusauthoridChernyshov, DO=14059433800en_US
dc.identifier.scopusauthoridDogiel, VA=6603566238en_US

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