Characterizing the quiescent X-ray variability of the black hole low-mass X-ray binary V404 Cyg

F. Bernardini, E. M. Cackett

    Research output: Contribution to journalArticlepeer-review


    We conducted the first long-term (75 d) X-ray monitoring of the black hole low-mass X-ray binary V404 Cyg, with the goal of understanding and characterizing its variability during quiescence. The X-ray light curve of V404 Cyg shows several flares on time-scales of hours with a count rate change of a factor of about 5-8. The root-mean-square variability is Fvar = 57.0 ± 3.2 per cent. The first-order structure function is consistent with both a power spectrum of index -1 (flicker noise), or with a power spectrum of index 0 (white noise), implying that the light curve is variable on time-scales from days to months. The X-ray spectrum is well fitted by a power law with spectral index τ = 2.10-2.35, and we found that the spectral shape remains roughly constant as the flux changes. A constant spectral shape with respect to a change in the X-ray flux may favour a scenario in which the X-ray emission is dominated by synchrotron radiation produced in a jet.

    Original languageEnglish (US)
    Pages (from-to)2771-2780
    Number of pages10
    JournalMonthly Notices of the Royal Astronomical Society
    Issue number3
    StatePublished - Apr 2014


    • Accretion, accretion discs-black hole physics-stars
    • Binaries-X-rays
    • Black holes -X-rays
    • Individual
    • V404 Cyg

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science


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