GRS 1739-278 OBSERVED AT VERY LOW LUMINOSITY WITH XMM-NEWTON AND NuSTAR

ABSTRACT We present a detailed spectral analysis of XMM-Newton and NuSTAR observations of the accreting transient black hole GRS 1739−278 during a very faint low hard state at ∼0.02% of the Eddington luminosity (for a distance of 8.5 kpc and a mass of 10 ). The broadband X-ray spectrum between 0.5 a...

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Published in:The Astrophysical journal 2016-12, Vol.832 (2), p.115
Main Authors: Fürst, F., Tomsick, J. A., Yamaoka, K., Dauser, T., Miller, J. M., Clavel, M., Corbel, S., Fabian, A., García, J., Harrison, F. A., Loh, A., Kaaret, P., Kalemci, E., Migliari, S., Miller-Jones, J. C. A., Pottschmidt, K., Rahoui, F., Rodriguez, J., Stern, D., Stuhlinger, M., Walton, D. J., Wilms, J.
Format: Article
Language:English
Subjects:
ACCRETION DISKS
accretion, accretion disks
Astrophysics
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BLACK HOLES
Broadband
Confidence limits
DISTANCE
EMISSIVITY
High Energy Astrophysical Phenomena
INCLINATION
KEV RANGE
LUMINOSITY
MASS
PHOTONS
Physics
Power law
REFLECTION
Spectral analysis
Spectrum analysis
STARS
stars: black holes
X RADIATION
X-RAY SPECTRA
X-rays: binaries
X-rays: individual (GRS 1739-278)
XMM (spacecraft)
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Summary:ABSTRACT We present a detailed spectral analysis of XMM-Newton and NuSTAR observations of the accreting transient black hole GRS 1739−278 during a very faint low hard state at ∼0.02% of the Eddington luminosity (for a distance of 8.5 kpc and a mass of 10 ). The broadband X-ray spectrum between 0.5 and 60 keV can be well-described by a power-law continuum with an exponential cutoff. The continuum is unusually hard for such a low luminosity, with a photon index of Γ = 1.39 0.04. We find evidence for an additional reflection component from an optically thick accretion disk at the 98% likelihood level. The reflection fraction is low, with . In combination with measurements of the spin and inclination parameters made with NuSTAR during a brighter hard state by Miller et al., we seek to constrain the accretion disk geometry. Depending on the assumed emissivity profile of the accretion disk, we find a truncation radius of 15-35 (5-12 ) at the 90% confidence limit. These values depend strongly on the assumptions and we discuss possible systematic uncertainties.
ISSN:0004-637X
1538-4357
DOI:10.3847/0004-637X/832/2/115