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The advection-dominated accretion flow for the anticorrelation between the X-ray photon index and the X-ray luminosity in neutron star low-mass X-ray binaries
Qiao, Erlin1,2; Liu, B. F.1,2
2020-08-01
Source PublicationMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
ISSN0035-8711
Volume496Issue:3Pages:2704-2714
AbstractObservationally, an anticorrelation between the X-ray photon index Gamma (obtained by fitting the X-ray spectrum between 0.5 and 10 keV with a single power law) and the X-ray luminosity L0.5-10 keV, i.e. a softening of the X-ray spectrum with decreasing L0.5-10 keV, is found in neutron star low-mass X-ray binaries (NS-LMXBs) in the range of L0.5-10 keV similar to 10(34)-10(36) erg s(-1) In this paper, we explain the observed anticorrelation between Gamma and L(0.5-10 keV )within the framework of the self-similar solution of the advection-dominated accretion flow (ADAF) around a weakly magnetized NS. The ADAF model intrinsically predicts an anticorrelation between Gamma and L0.5-10 keV. In the ADAF model, there is a key parameter, fth, which describes the fraction of the ADAF energy released at the surface of the NS as thermal emission to be scattered in the ADAF. We test the effect of fth on the anticorrelation between Gamma and L0.5-10 keV. It is found that the value of fth can significantly affect the anticorrelation between Gamma and L0.5-10 keV. Specifically, the anticorrelation between Gamma and L0.5-10 keV becomes flatter with decreasing fth as taking fth = 0.1, 0.03, 0.01, 0.005, 0.003, and 0, respectively. By comparing with a sample of non-pulsating NS-LMXBs with well measured Gamma and L0.5-10 keV, we find that indeed only a small value of 0.003 less than or similar to fth less than or similar to 0.1 is needed to match the observed anticorrelation between Gamma and L0.5-10 keV. Finally, we argue that the small value of fth less than or similar to 0.1 derived in this paper further confirms our previous conclusion that the radiative efficiency of NSs with an ADAF accretion may not be as high as epsilon similar to MGM/R-* Mc(2) similar to 0.2.
Keywordaccretion, accretion discs black hole physics stars: neutron X-rays: binaries
Funding OrganizationNational Natural Science Foundation of China ; National Natural Science Foundation of China ; gravitational wave pilot B ; gravitational wave pilot B ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; National Program on Key Research and Development Project ; National Program on Key Research and Development Project ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; gravitational wave pilot B ; gravitational wave pilot B ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; National Program on Key Research and Development Project ; National Program on Key Research and Development Project ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; gravitational wave pilot B ; gravitational wave pilot B ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; National Program on Key Research and Development Project ; National Program on Key Research and Development Project ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; gravitational wave pilot B ; gravitational wave pilot B ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; National Program on Key Research and Development Project ; National Program on Key Research and Development Project
DOI10.1093/mnras/staa1671
WOS KeywordSPECTRAL EVOLUTION ; 2008 OUTBURST ; BLACK-HOLES ; RADIO ; ORIGIN ; QUIESCENCE ; EMISSION ; BEHAVIOR ; STATES
Language英语
Funding ProjectNational Natural Science Foundation of China[11773037] ; National Natural Science Foundation of China[11673026] ; gravitational wave pilot B[XDB23040100] ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences[XDA15052100] ; National Program on Key Research and Development Project[2016YFA0400804]
Funding OrganizationNational Natural Science Foundation of China ; National Natural Science Foundation of China ; gravitational wave pilot B ; gravitational wave pilot B ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; National Program on Key Research and Development Project ; National Program on Key Research and Development Project ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; gravitational wave pilot B ; gravitational wave pilot B ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; National Program on Key Research and Development Project ; National Program on Key Research and Development Project ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; gravitational wave pilot B ; gravitational wave pilot B ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; National Program on Key Research and Development Project ; National Program on Key Research and Development Project ; National Natural Science Foundation of China ; National Natural Science Foundation of China ; gravitational wave pilot B ; gravitational wave pilot B ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; Strategic Pioneer Program on Space Science, Chinese Academy of Sciences ; National Program on Key Research and Development Project ; National Program on Key Research and Development Project
WOS Research AreaAstronomy & Astrophysics
WOS SubjectAstronomy & Astrophysics
WOS IDWOS:000562471000013
PublisherOXFORD UNIV PRESS
Citation statistics
Document Type期刊论文
Identifierhttp://ir.bao.ac.cn/handle/114a11/82292
Collection中国科学院国家天文台
Corresponding AuthorQiao, Erlin
Affiliation1.Chinese Acad Sci, Natl Astron Observ, Key Lab Space Astron & Technol, Beijing 100012, Peoples R China
2.Univ Chinese Acad Sci, Sch Astron & Space Sci, 19A Yuquan Rd, Beijing 100049, Peoples R China
Recommended Citation
GB/T 7714
Qiao, Erlin,Liu, B. F.. The advection-dominated accretion flow for the anticorrelation between the X-ray photon index and the X-ray luminosity in neutron star low-mass X-ray binaries[J]. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,2020,496(3):2704-2714.
APA Qiao, Erlin,&Liu, B. F..(2020).The advection-dominated accretion flow for the anticorrelation between the X-ray photon index and the X-ray luminosity in neutron star low-mass X-ray binaries.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY,496(3),2704-2714.
MLA Qiao, Erlin,et al."The advection-dominated accretion flow for the anticorrelation between the X-ray photon index and the X-ray luminosity in neutron star low-mass X-ray binaries".MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 496.3(2020):2704-2714.
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