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Article: Can accretion disk properties distinguish gravastars from black holes?

TitleCan accretion disk properties distinguish gravastars from black holes?
Authors
KeywordsGravitation and cosmology
Particle physics and field theory
Astrophysics and astroparticles
Issue Date2009
PublisherInstitute of Physics Publishing. The Journal's web site is located at http://www.iop.org/EJ/cqg
Citation
Classical and Quantum Gravity, 2009, v. 26 n. 21, article no. 215006 How to Cite?
AbstractGravastars, hypothetic astrophysical objects, consisting of a dark energy condensate surrounded by a strongly correlated thin shell of anisotropic matter, have been proposed as an alternative to the standard black hole picture of general relativity. Observationally distinguishing between astrophysical black holes and gravastars is a major challenge for this latter theoretical model. This is due to the fact that in static gravastars large stability regions (of the transition layer of these configurations) exist that are sufficiently close to the expected position of the event horizon, so that it would be difficult to distinguish the exterior geometry of gravastars from an astrophysical black hole. However, in the context of stationary and axially symmetrical geometries, a possibility of distinguishing gravastars from black holes is through the comparative study of thin accretion disks around rotating gravastars and Kerr-type black holes, respectively. In the present paper, we consider accretion disks around slowly rotating gravastars, with all the metric tensor components estimated up to the second order in the angular velocity. Due to the differences in the exterior geometry, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution and equilibrium radiation spectrum) are different for these two classes of compact objects, consequently giving clear observational signatures. In addition to this, it is also shown that the conversion efficiency of the accreting mass into radiation is always smaller than the conversion efficiency for black holes, i.e. gravastars provide a less efficient mechanism for converting mass to radiation than black holes. Thus, these observational signatures provide the possibility of clearly distinguishing rotating gravastars from Kerr-type black holes. © 2009 IOP Publishing Ltd.
Persistent Identifierhttp://hdl.handle.net/10722/125293
ISSN
2015 Impact Factor: 2.837
2015 SCImago Journal Rankings: 1.633
ISI Accession Number ID
Funding AgencyGrant Number
General Research Fund701808P
Hungarian ScientificResearch Fund (OTKA)69036
Funding Information:

We would like to thank the two anonymous referees for suggestions and comments that helped us to significantly improve the manuscript. The work of TH was supported by the General Research Fund grant number HKU 701808P of the government of the Hong Kong Special Administrative Region. ZKwas supported by the Hungarian ScientificResearch Fund (OTKA) grant no 69036.

 

DC FieldValueLanguage
dc.contributor.authorHarko, Ten_HK
dc.contributor.authorKovacs, Zen_HK
dc.contributor.authorLobo, FSNen_HK
dc.date.accessioned2010-10-31T11:22:46Z-
dc.date.available2010-10-31T11:22:46Z-
dc.date.issued2009en_HK
dc.identifier.citationClassical and Quantum Gravity, 2009, v. 26 n. 21, article no. 215006en_HK
dc.identifier.issn0264-9381en_HK
dc.identifier.urihttp://hdl.handle.net/10722/125293-
dc.description.abstractGravastars, hypothetic astrophysical objects, consisting of a dark energy condensate surrounded by a strongly correlated thin shell of anisotropic matter, have been proposed as an alternative to the standard black hole picture of general relativity. Observationally distinguishing between astrophysical black holes and gravastars is a major challenge for this latter theoretical model. This is due to the fact that in static gravastars large stability regions (of the transition layer of these configurations) exist that are sufficiently close to the expected position of the event horizon, so that it would be difficult to distinguish the exterior geometry of gravastars from an astrophysical black hole. However, in the context of stationary and axially symmetrical geometries, a possibility of distinguishing gravastars from black holes is through the comparative study of thin accretion disks around rotating gravastars and Kerr-type black holes, respectively. In the present paper, we consider accretion disks around slowly rotating gravastars, with all the metric tensor components estimated up to the second order in the angular velocity. Due to the differences in the exterior geometry, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution and equilibrium radiation spectrum) are different for these two classes of compact objects, consequently giving clear observational signatures. In addition to this, it is also shown that the conversion efficiency of the accreting mass into radiation is always smaller than the conversion efficiency for black holes, i.e. gravastars provide a less efficient mechanism for converting mass to radiation than black holes. Thus, these observational signatures provide the possibility of clearly distinguishing rotating gravastars from Kerr-type black holes. © 2009 IOP Publishing Ltd.-
dc.languageengen_HK
dc.publisherInstitute of Physics Publishing. The Journal's web site is located at http://www.iop.org/EJ/cqgen_HK
dc.relation.ispartofClassical and Quantum Gravityen_HK
dc.rightsCreative Commons: Attribution 3.0 Hong Kong License-
dc.rightsClassical and Quantum Gravity. Copyright © Institute of Physics Publishing.-
dc.subjectGravitation and cosmology-
dc.subjectParticle physics and field theory-
dc.subjectAstrophysics and astroparticles-
dc.titleCan accretion disk properties distinguish gravastars from black holes?en_HK
dc.typeArticleen_HK
dc.identifier.openurlhttp://library.hku.hk:4550/resserv?sid=HKU:IR&issn=0264-9381&volume=26&issue=21, article no. 215006&spage=&epage=&date=2009&atitle=Can+accretion+disk+properties+distinguish+gravastars+from+black+holes?en_HK
dc.identifier.emailHarko, T: harko@HKUCC.hku.hken_HK
dc.identifier.emailKovacs, Z: zkovacs@mpifr-bonn.mpg.de-
dc.identifier.emailLobo, FSN: flobo@cii.fc.ul.pt-
dc.identifier.authorityHarko, T=rp01333en_HK
dc.description.naturepostprint-
dc.identifier.doi10.1088/0264-9381/26/21/215006-
dc.identifier.scopuseid_2-s2.0-70350591187-
dc.identifier.hkuros169441en_HK
dc.identifier.volume26en_HK
dc.identifier.issue21, article no. 215006-
dc.identifier.isiWOS:000270903900007-

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