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Article: Can accretion disk properties distinguish gravastars from black holes?
Title | Can accretion disk properties distinguish gravastars from black holes? | ||||||
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Authors | |||||||
Keywords | Gravitation and cosmology Particle physics and field theory Astrophysics and astroparticles | ||||||
Issue Date | 2009 | ||||||
Publisher | Institute 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? | ||||||
Abstract | Gravastars, 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 Identifier | http://hdl.handle.net/10722/125293 | ||||||
ISSN | 2023 Impact Factor: 3.6 2023 SCImago Journal Rankings: 1.232 | ||||||
ISI Accession Number ID |
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 Field | Value | Language |
---|---|---|
dc.contributor.author | Harko, T | en_HK |
dc.contributor.author | Kovacs, Z | en_HK |
dc.contributor.author | Lobo, FSN | en_HK |
dc.date.accessioned | 2010-10-31T11:22:46Z | - |
dc.date.available | 2010-10-31T11:22:46Z | - |
dc.date.issued | 2009 | en_HK |
dc.identifier.citation | Classical and Quantum Gravity, 2009, v. 26 n. 21, article no. 215006 | en_HK |
dc.identifier.issn | 0264-9381 | en_HK |
dc.identifier.uri | http://hdl.handle.net/10722/125293 | - |
dc.description.abstract | Gravastars, 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.language | eng | en_HK |
dc.publisher | Institute of Physics Publishing. The Journal's web site is located at http://www.iop.org/EJ/cqg | en_HK |
dc.relation.ispartof | Classical and Quantum Gravity | en_HK |
dc.rights | Classical and Quantum Gravity. Copyright © Institute of Physics Publishing. | - |
dc.subject | Gravitation and cosmology | - |
dc.subject | Particle physics and field theory | - |
dc.subject | Astrophysics and astroparticles | - |
dc.title | Can accretion disk properties distinguish gravastars from black holes? | en_HK |
dc.type | Article | en_HK |
dc.identifier.openurl | http://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.email | Harko, T: harko@HKUCC.hku.hk | en_HK |
dc.identifier.email | Kovacs, Z: zkovacs@mpifr-bonn.mpg.de | - |
dc.identifier.email | Lobo, FSN: flobo@cii.fc.ul.pt | - |
dc.identifier.authority | Harko, T=rp01333 | en_HK |
dc.description.nature | postprint | - |
dc.identifier.doi | 10.1088/0264-9381/26/21/215006 | - |
dc.identifier.scopus | eid_2-s2.0-70350591187 | - |
dc.identifier.hkuros | 169441 | en_HK |
dc.identifier.volume | 26 | en_HK |
dc.identifier.issue | 21, article no. 215006 | - |
dc.identifier.isi | WOS:000270903900007 | - |
dc.identifier.issnl | 0264-9381 | - |