GRS 1739-278 observed at very low luminosity with XMM-NEWTON and NuSTAR
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 M ). The broad-band X-ray spectrum between 0.5–60 ke...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal Article |
| Published: |
Institute of Physics Publishing
2016
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| Online Access: | http://purl.org/au-research/grants/arc/FT140101082 http://hdl.handle.net/20.500.11937/10029 |
| Summary: | 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 M ). The broad-band X-ray spectrum between 0.5–60 keV can be welldescribed 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 Rrefl = 0.043+0.033
−0.023. In combination with measurements of the spin and inclination parameters made
with NuSTAR during a brighter hard state by Miller and co-workers, 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 Rg (5–12 RISCO) at the 90% confiden |
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