Effects of Strong Photospheric Dissipation on the Spectra and Structure of Accretion Disks with Non-zero Inner Torque

TL;DR

This paper models accretion disk spectra near the Eddington limit, showing how photospheric dissipation and inner torque influence spectral features and QPO characteristics in black hole X-ray binaries.

Contribution

It introduces numerical models incorporating non-zero inner torque and photospheric dissipation profiles based on 3D simulations, advancing understanding of spectral and QPO behaviors.

Findings

Photospheric dissipation produces steep power-law spectra.

Inner torque shifts spectral peaks to higher energies.

Higher photospheric dissipation correlates with increased QPO quality factors.

Abstract

We present numerical calculations of spectra and structure of accretion disks models appropriate for near-Eddington luminosity black hole X-ray binaries (BHB). Our work incorporates non-zero torque at the ISCO as well as several dissipation profiles based on first-principles three-dimensional disk interior simulations. We found that significant dissipation near the photosphere can produce steep power law-like spectra for models with moderate viewing angles spanning a range of black hole spins while including inner torque push the spectral peak to higher energies. Consistent with previous studies, we also conclude that disks with stresses at the inner edge remain viable models for high-frequency quasi-periodic oscillations (HFQPO), especially given that increasing dissipation near the photospheres actually resulted in QPO power spectra with higher quality factors compared to those found in recent work.