Optical and near-infrared spectroscopy of the black hole GX 339-4 - I. A focus on the continuum in the low/hard and high/soft states

F. Rahoui, M. Coriat, S. Corbel, M. Cadolle Bel, J. A. Tomsick, J. C. Lee, J. Rodriguez, Dave Russell, S. Migliari

    Research output: Contribution to journalArticle

    Abstract

    The microquasar GX 339-4, known to exhibit powerful compact jets that dominate its radio to near-infrared emission, entered an outburst in 2010 for the fifth time in about 15yr. An extensive radio to X-ray multiwavelength campaign was immediately triggered, and we report here on European Southern Observatory/FORS2+ISAAC optical and near-infrared spectroscopic observations, supported by Australia Telescope Compact Array radio and Rossi X-ray Timing Experiment/Swift X-ray quasi-simultaneous data. GX 339-4 was observed at three different epochs, once in the soft state and twice in the hard state. In the soft state, the optical and near-infrared continuum is largely consistent with the Raleigh-Jeans tail of a thermal process. As an explanation, we favour irradiation of the outer accretion disc by its inner regions, enhanced by disc warping. An excess is also present at low frequencies, likely due to an M subgiant companion star. During the first hard state, the optical/near-infrared continuum is well described by the optically thin synchrotron emission of the compact jet combined with disc irradiation and perhaps another component peaking in the ultraviolet. The spectral break where the jet transits from the optically thick to thin regimes, located below 1.20 × 10 14Hz, is not detected and the extension of the optically thin synchrotron is consistent with the 3-50keV spectrum. In contrast, the emission during the second hard state is more difficult to understand and points towards a more complex jet continuum. In both cases, the near-infrared continuum is found to be variable at time-scales at least as short as 20s, although these variabilities are smoothed out beyond a few hundred seconds. This implies rapid variations - in flux and frequency - of the location of the spectral break, i.e. dramatic short time-scale changes of the physical conditions at the base of the jet, such as the magnetic field and/or the base radius.

    Original languageEnglish (US)
    Pages (from-to)2202-2212
    Number of pages11
    JournalMonthly Notices of the Royal Astronomical Society
    Volume422
    Issue number3
    DOIs
    StatePublished - May 1 2012

    Fingerprint

    infrared spectroscopy
    near infrared
    continuums
    radio
    irradiation
    synchrotrons
    subgiant stars
    time measurement
    timescale
    companion stars
    x rays
    transit
    European Southern Observatory
    accretion disks
    outburst
    observatory
    accretion
    telescopes
    low frequencies
    magnetic field

    Keywords

    • Accretion, accretion discs
    • Binaries: close
    • Infrared: stars
    • ISM: jets and outflows
    • Stars: individual: GX 339-4
    • X-rays: binaries

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    Optical and near-infrared spectroscopy of the black hole GX 339-4 - I. A focus on the continuum in the low/hard and high/soft states. / Rahoui, F.; Coriat, M.; Corbel, S.; Cadolle Bel, M.; Tomsick, J. A.; Lee, J. C.; Rodriguez, J.; Russell, Dave; Migliari, S.

    In: Monthly Notices of the Royal Astronomical Society, Vol. 422, No. 3, 01.05.2012, p. 2202-2212.

    Research output: Contribution to journalArticle

    Rahoui, F, Coriat, M, Corbel, S, Cadolle Bel, M, Tomsick, JA, Lee, JC, Rodriguez, J, Russell, D & Migliari, S 2012, 'Optical and near-infrared spectroscopy of the black hole GX 339-4 - I. A focus on the continuum in the low/hard and high/soft states', Monthly Notices of the Royal Astronomical Society, vol. 422, no. 3, pp. 2202-2212. https://doi.org/10.1111/j.1365-2966.2012.20763.x
    Rahoui, F. ; Coriat, M. ; Corbel, S. ; Cadolle Bel, M. ; Tomsick, J. A. ; Lee, J. C. ; Rodriguez, J. ; Russell, Dave ; Migliari, S. / Optical and near-infrared spectroscopy of the black hole GX 339-4 - I. A focus on the continuum in the low/hard and high/soft states. In: Monthly Notices of the Royal Astronomical Society. 2012 ; Vol. 422, No. 3. pp. 2202-2212.
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    AU - Coriat, M.

    AU - Corbel, S.

    AU - Cadolle Bel, M.

    AU - Tomsick, J. A.

    AU - Lee, J. C.

    AU - Rodriguez, J.

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    AU - Migliari, S.

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