2 research outputs found
Relativistic Accretion Disk Models of High State Black Hole X-ray Binary Spectra
We present calculations of non-LTE, relativistic accretion disk models
applicable to the high/soft state of black hole X-ray binaries. We include the
effects of thermal Comptonization and bound-free and free-free opacities of all
abundant ion species. We present spectra calculated for a variety of accretion
rates, black hole spin parameters, disk inclinations, and stress prescriptions.
We also consider nonzero inner torques on the disk, and explore different
vertical dissipation profiles, including some which are motivated by recent
radiation MHD simulations of magnetorotational turbulence. Bound-free metal
opacity generally produces significantly less spectral hardening than previous
models which only considered Compton scattering and free-free opacity. It also
tends to keep the effective photosphere near the surface, resulting in spectra
which are remarkably independent of the stress prescription and vertical
dissipation profile, provided little dissipation occurs above the effective
photosphere. We provide detailed comparisons between our models and the widely
used multicolor disk model. Frequency dependent discrepancies exist that may
affect the parameters of other spectral components when this simpler disk model
is used to fit modern X-ray data. For a given source, our models predict that
the luminosity in the high/soft state should approximately scale with the
fourth power of the empirically inferred maximum temperature, but with a slight
hardening at high luminosities. This is in good agreement with observations.
(abridged)Comment: 30 pages, 18 figures, submitted to ApJ; corrected reference