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Article: Annihilation emission from the galactic black hole
Title | Annihilation emission from the galactic black hole |
---|---|
Authors | |
Keywords | Black Hole Physics Cosmic Rays Galaxy: Center Gamma Rays: Theory Radiation Mechanisms: Nonthermal |
Issue Date | 2006 |
Publisher | Institute 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? |
Abstract | Both 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 Identifier | http://hdl.handle.net/10722/175026 |
ISSN | 2023 Impact Factor: 8.8 2023 SCImago Journal Rankings: 2.766 |
ISI Accession Number ID | |
References |
DC Field | Value | Language |
---|---|---|
dc.contributor.author | Cheng, KS | en_US |
dc.contributor.author | Chernyshov, DO | en_US |
dc.contributor.author | Dogiel, VA | en_US |
dc.date.accessioned | 2012-11-26T08:48:50Z | - |
dc.date.available | 2012-11-26T08:48:50Z | - |
dc.date.issued | 2006 | en_US |
dc.identifier.citation | Astrophysical Journal Letters, 2006, v. 645 n. 2 I, p. 1138-1151 | en_US |
dc.identifier.issn | 2041-8205 | en_US |
dc.identifier.uri | http://hdl.handle.net/10722/175026 | - |
dc.description.abstract | Both 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.language | eng | en_US |
dc.publisher | Institute of Physics Publishing Ltd. The Journal's web site is located at http://iopscience.iop.org/2041-8205 | en_US |
dc.relation.ispartof | Astrophysical Journal Letters | en_US |
dc.subject | Black Hole Physics | en_US |
dc.subject | Cosmic Rays | en_US |
dc.subject | Galaxy: Center | en_US |
dc.subject | Gamma Rays: Theory | en_US |
dc.subject | Radiation Mechanisms: Nonthermal | en_US |
dc.title | Annihilation emission from the galactic black hole | en_US |
dc.type | Article | en_US |
dc.identifier.email | Cheng, KS: hrspksc@hkucc.hku.hk | en_US |
dc.identifier.authority | Cheng, KS=rp00675 | en_US |
dc.description.nature | link_to_subscribed_fulltext | en_US |
dc.identifier.doi | 10.1086/504583 | en_US |
dc.identifier.scopus | eid_2-s2.0-33746928399 | en_US |
dc.relation.references | http://www.scopus.com/mlt/select.url?eid=2-s2.0-33746928399&selection=ref&src=s&origin=recordpage | en_US |
dc.identifier.volume | 645 | en_US |
dc.identifier.issue | 2 I | en_US |
dc.identifier.spage | 1138 | en_US |
dc.identifier.epage | 1151 | en_US |
dc.identifier.isi | WOS:000239053900032 | - |
dc.publisher.place | United Kingdom | en_US |
dc.identifier.scopusauthorid | Cheng, KS=9745798500 | en_US |
dc.identifier.scopusauthorid | Chernyshov, DO=14059433800 | en_US |
dc.identifier.scopusauthorid | Dogiel, VA=6603566238 | en_US |
dc.identifier.issnl | 2041-8205 | - |