Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei

Observations and interpretation

Qi Xiang Yang, Fu Guo Xie, Feng Yuan, Andrzej A. Zdziarski, Marek Gierliński, Luis C. Ho, Zhaolong Yu

    Research output: Contribution to journalArticle

    39 Citations (Scopus)

    Abstract

    We investigate the observed correlation between the 2-10 keV X-ray luminosity (in unit of the Eddington luminosity; lX ≡ LX/LEdd) and the photon index (G{cyrillic}) of the X-ray spectrum for both black hole X-ray binaries (BHBs) and active galactic nuclei (AGNs). We construct a large sample, with 10-9 ≲ lX ≲ 10-1. We find that G{cyrillic} is positively and negatively correlated with lX when lX ≳ 10-3 and 10-6.5 ≲ lX ≲ 10-3, respectively, while G{cyrillic} is nearly a constant when lX ≲ 10-6.5. We explain the above correlation in the framework of a coupled hot accretion flow-jet model. The radio emission always comes from the jet while the X-ray emission comes from the accretion flow and jet when lX is above and below 10-6.5, respectively. More specifically, we assume that with the increase of mass accretion rate, the hot accretion flow develops into a clumpy and further a disc-corona two-phase structure because of thermal instability. We argue that such kind of two-phase accretion flow can explain the observed positive correlation.

    Original languageEnglish
    Pages (from-to)1692-1704
    Number of pages13
    JournalMonthly Notices of the Royal Astronomical Society
    Volume447
    Issue number2
    DOIs
    Publication statusPublished - 21 Feb 2015

    Fingerprint

    active galactic nuclei
    accretion
    luminosity
    photons
    x rays
    jet flow
    thermal instability
    radio emission
    coronas
    corona
    index
    radio

    Keywords

    • Accretion
    • Accretion discs
    • Galaxies: active
    • Quasars: general
    • X-rays: binaries
    • X-rays: general

    Cite this

    @article{5d3a91d4cfaf41cba405f0d9f403956a,
    title = "Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei: Observations and interpretation",
    abstract = "We investigate the observed correlation between the 2-10 keV X-ray luminosity (in unit of the Eddington luminosity; lX ≡ LX/LEdd) and the photon index (G{cyrillic}) of the X-ray spectrum for both black hole X-ray binaries (BHBs) and active galactic nuclei (AGNs). We construct a large sample, with 10-9 ≲ lX ≲ 10-1. We find that G{cyrillic} is positively and negatively correlated with lX when lX ≳ 10-3 and 10-6.5 ≲ lX ≲ 10-3, respectively, while G{cyrillic} is nearly a constant when lX ≲ 10-6.5. We explain the above correlation in the framework of a coupled hot accretion flow-jet model. The radio emission always comes from the jet while the X-ray emission comes from the accretion flow and jet when lX is above and below 10-6.5, respectively. More specifically, we assume that with the increase of mass accretion rate, the hot accretion flow develops into a clumpy and further a disc-corona two-phase structure because of thermal instability. We argue that such kind of two-phase accretion flow can explain the observed positive correlation.",
    keywords = "Accretion, Accretion discs, Galaxies: active, Quasars: general, X-rays: binaries, X-rays: general",
    author = "Yang, {Qi Xiang} and Xie, {Fu Guo} and Feng Yuan and Zdziarski, {Andrzej A.} and Marek Gierliński and Ho, {Luis C.} and Zhaolong Yu",
    year = "2015",
    month = "2",
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    language = "English",
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    pages = "1692--1704",
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    Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei : Observations and interpretation. / Yang, Qi Xiang; Xie, Fu Guo; Yuan, Feng; Zdziarski, Andrzej A.; Gierliński, Marek; Ho, Luis C.; Yu, Zhaolong.

    In: Monthly Notices of the Royal Astronomical Society, Vol. 447, No. 2, 21.02.2015, p. 1692-1704.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Correlation between the photon index and X-ray luminosity of black hole X-ray binaries and active galactic nuclei

    T2 - Observations and interpretation

    AU - Yang, Qi Xiang

    AU - Xie, Fu Guo

    AU - Yuan, Feng

    AU - Zdziarski, Andrzej A.

    AU - Gierliński, Marek

    AU - Ho, Luis C.

    AU - Yu, Zhaolong

    PY - 2015/2/21

    Y1 - 2015/2/21

    N2 - We investigate the observed correlation between the 2-10 keV X-ray luminosity (in unit of the Eddington luminosity; lX ≡ LX/LEdd) and the photon index (G{cyrillic}) of the X-ray spectrum for both black hole X-ray binaries (BHBs) and active galactic nuclei (AGNs). We construct a large sample, with 10-9 ≲ lX ≲ 10-1. We find that G{cyrillic} is positively and negatively correlated with lX when lX ≳ 10-3 and 10-6.5 ≲ lX ≲ 10-3, respectively, while G{cyrillic} is nearly a constant when lX ≲ 10-6.5. We explain the above correlation in the framework of a coupled hot accretion flow-jet model. The radio emission always comes from the jet while the X-ray emission comes from the accretion flow and jet when lX is above and below 10-6.5, respectively. More specifically, we assume that with the increase of mass accretion rate, the hot accretion flow develops into a clumpy and further a disc-corona two-phase structure because of thermal instability. We argue that such kind of two-phase accretion flow can explain the observed positive correlation.

    AB - We investigate the observed correlation between the 2-10 keV X-ray luminosity (in unit of the Eddington luminosity; lX ≡ LX/LEdd) and the photon index (G{cyrillic}) of the X-ray spectrum for both black hole X-ray binaries (BHBs) and active galactic nuclei (AGNs). We construct a large sample, with 10-9 ≲ lX ≲ 10-1. We find that G{cyrillic} is positively and negatively correlated with lX when lX ≳ 10-3 and 10-6.5 ≲ lX ≲ 10-3, respectively, while G{cyrillic} is nearly a constant when lX ≲ 10-6.5. We explain the above correlation in the framework of a coupled hot accretion flow-jet model. The radio emission always comes from the jet while the X-ray emission comes from the accretion flow and jet when lX is above and below 10-6.5, respectively. More specifically, we assume that with the increase of mass accretion rate, the hot accretion flow develops into a clumpy and further a disc-corona two-phase structure because of thermal instability. We argue that such kind of two-phase accretion flow can explain the observed positive correlation.

    KW - Accretion

    KW - Accretion discs

    KW - Galaxies: active

    KW - Quasars: general

    KW - X-rays: binaries

    KW - X-rays: general

    UR - http://www.scopus.com/inward/record.url?scp=84922573971&partnerID=8YFLogxK

    U2 - 10.1093/mnras/stu2571

    DO - 10.1093/mnras/stu2571

    M3 - Article

    VL - 447

    SP - 1692

    EP - 1704

    JO - Monthly Notices of the Royal Astronomical Society

    JF - Monthly Notices of the Royal Astronomical Society

    SN - 0035-8711

    IS - 2

    ER -