2006/06/25 by Jeremy D. Schnittman, Julian H. Krolik, John F. Hawley · 8 citations
Physics and Astronomy · #Accretion (finance) #Amplitude #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #Astrophysics and Star Formation Studies #Black hole (networking) #Black-body radiation #Light curve #Magnetohydrodynamics #Radiative transfer #Schwarzschild radius #Spectral density #astro-ph
paper · pdf · doi:10.1086/507421
published as Astrophys.J.651:1031-1048,2006 · Accepted to ApJ, 43 pages, 13 figures, 2 tables
arxiv created 2006/06/25 · openalex publication_date 2006/11/02 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We use a relativistic ray-tracing code to calculate the light curves observed from a global, general relativistic, magnetohydrodynamic simulation of an accretion flow onto a Schwarzschild black hole. We apply three basic emission models to sample different properties of the time-dependent accretion disk. With one of these models, which assumes thermal blackbody emission and free-free absorption, we can predict qualitative features of the high-frequency power spectrum from stellar-mass black holes in the "thermal dominant" state. The simulated power spectrum is characterized by a power law of index Γ ≈ 3 and total rms fractional variance of ≲2% above 10 Hz. For each emission model, we find that the variability amplitude should increase with increasing inclination angle. On the basis of a newly developed formalism for quantifying the significance of quasi-periodic oscillations (QPOs) in simulation data, we find that these simulations are able to identify any such features with (rms/mean) amplitudes ≳1% near the orbital frequency at the innermost stable orbit. Initial results indicate the existence of transient QPO peaks with frequency ratios of nearly 2 : 3 at a 99.9% confidence limit, but they are not generic features, because at any given time they are seen only from certain observer directions. In addition, we present detailed analysis of the azimuthal structure of the accretion disk and the evolution of density perturbations in the inner disk. These "hot-spot" structures appear to be roughly self-similar over a range of disk radii, with a single characteristic size δϕ = 25 ° and δ r / r = 0.3, and typical lifetimes T l ≈ 0.3 T orb .