Analysis of accretion disc structure and stability using open code for vertical structure
Abstract
Radial structure of accretion discs around compact objects is often described using analytic approximations which are derived from averaging or integrating vertical structure equations. For nonsolar chemical composition, partial ionization, or for supermassive black holes, this approach is not accurate. Additionally, radial extension of 'analyticallydescribed' disc zones is not evident in many cases. We calculate vertical structure of accretion discs around compact objects, with and without external irradiation, with radiative and convective energy transport taken into account. For this, we introduce a new open PYTHON code, allowing different equations of state and opacity laws, including tabular values. As a result, radial structure and stability 'Scurves' are calculated for specific disc parameters and chemical composition. In particular, based on more accurate powerlaw approximations for opacity in the disc, we supply new analytic formulas for the farthest regions of the hot disc around stellarmass object. On calculating vertical structure of a selfirradiated disc, we calculate a selfconsistent value of the irradiation parameter C_{irr} for stationary αdisc. We find that, for a fixed shape of the Xray spectrum, C_{irr} depends weakly on the accretion rate but changes with radius, and the dependence is driven by the conditions in the photosphere and disc opening angle. The hot zone extent depends on the ratio between irradiating and intrinsic flux: corresponding relation for $T_{\rm irr,\, crit}$ is obtained.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 September 2023
 DOI:
 10.1093/mnras/stad1881
 arXiv:
 arXiv:2303.02184
 Bibcode:
 2023MNRAS.524.3647T
 Keywords:

 accretion;
 accretion discs;
 instabilities;
 Xrays: binaries;
 Astrophysics  High Energy Astrophysical Phenomena
 EPrint:
 Accepted for publication in MNRAS, 15 pages, 15 figures, 3 appendix