GRS 1739-278 observed at very low luminosity with XMM-Newton and NuSTAR
Autor: | Fuerst, F., Tomsick, J. A., Yamaoka, K., Dauser, T., Miller, J. M., Clavel, M., Corbel, S., Fabian, A. C., Garcia, 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. |
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Rok vydání: | 2016 |
Předmět: | |
Druh dokumentu: | Working Paper |
DOI: | 10.3847/0004-637X/832/2/115 |
Popis: | 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_sun ). The broad-band X-ray spectrum between 0.5-60 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 Gamma = 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 R_refl = 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 R_ISCO ) at the 90% confidence limit. These values depend strongly on the assumptions and we discuss possible systematic uncertainties. Comment: 7 pages, 3 figures, accepted for publication in ApJ |
Databáze: | arXiv |
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