2017/08/14 by S. Rapisarda, Stefano Rapisarda, Adam Ingram +2 · 41 citations
Engineering · Physics and Astronomy · #Accretion (finance) #Astrophysical Phenomena and Observations #Astrophysics #Binary number #Black hole (networking) #Coherence (philosophical gambling strategy) #Mechanics and Biomechanics Studies #Physics #RADIUS #Spectral density #astro-ph.HE
paper · pdf · doi:10.1093/mnras/stx2110
published in Monthly Notices of the Royal Astronomical Society 472(4), 3821-3832 (Oxford University Press) · 12 pages, 9 figures, 2 tables, accepted for publication in MNRAS
arxiv created 2017/08/14 · openalex publication_date 2017/08/18 · openalex created_date 2017/08/31 · arxiv updated 2017/10/11 · openalex updated_date 2026/08/05
We present a timing analysis of three Rossi X-ray Timing Explorer observations of the black hole binary Cygnus X-1 with the propagating mass accretion rate fluctuations model propfluc. The model simultaneously predicts power spectra, time lags and coherence of the variability as a function of energy. The observations cover the soft and hard states of the source, and the transition between the two. We find good agreement between model predictions and data in the hard and soft states. Our analysis suggests that in the soft state the fluctuations propagate in an optically thin hot flow extending up to large radii above and below a stable optically thick disc. In the hard state, our results are consistent with a truncated disc geometry, where the hot flow extends radially inside the inner radius of the disc. In the transition from soft to hard state, the characteristics of the rapid variability are too complex to be successfully described with propfluc. The surface density profile of the hot flow predicted by our model and the lack of quasi-periodic oscillations in the soft and hard states suggest that the spin of the black hole is aligned with the inner accretion disc and therefore probably with the rotational axis of the binary system.