Bradley, Charles K.; Hynes, Robert I.; Kong, Albert K. H.; Haswell, C. A.; Casares, J. and Gallo, E.
The Spectrum of the Black Hole X-Ray Nova V404 Cygni in Quiescence as Measured by XMM-Newton.
Astrophysical Journal, 667(1) pp. 427–432.
We present XMM-Newton observations of the black hole X-ray nova V404 Cyg in quiescence. Its quiescent spectrum can be best fitted by a simple power law with slope Γ~2. The spectra are consistent with that expected for the advection-dominated accretion flow (ADAF). V404 Cyg was roughly equal in luminosity compared to the previous observation of Chandra. We see variability of a factor of 4 during the observation. We find no evidence for the presence of fluorescent or H-like/He-like iron emission, with upper limits of 52 and 110 eV, respectively. The limit on the fluorescent emission is improved by a factor of 15 over the previous estimate, and the restriction on H-like/He-like emission is lower than predicted from models by a factor of roughly 2.
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