Hot boundary layers in symbiotic binaries ax persei and ci cygni.
Accretion disk boundary layer models are calculated for the symbiotic binaries AX Per and CI Cyg, using a time-dependent numerical code. Hot boundary layers are found with temperatures above 10 K, assuming for the accreting star a mass M* = 0.5 M0 and a radius R * = 0.2 R0. However, choosing a larger stellar radius or a smaller stellar mass leads to cooler boundary layers. The numerical solutions agree fairly well with the observational estimates of the hot component temperature during quiescence but do not reproduce the apparent drop in effective temperature seen during the outburst of AX Per and CI Cyg. The maximum effective temperature obtained in the boundary layer solutions increases as the mass accretion rate increases (M = 1-10 x 10 M0 yr 1) but then stays nearly constant as the mass accretion rate approaches the Eddington limit (in the present case, MEdd 10- M0 yr `). In this high accretion rate regime, the disk becomes geometrically thick (H/r 0.4), and the energy dissipated in the dynamical boundary layer is radiated outward to larger radii and advected into the star. The boundary layer luminosity is only 32 its expected value; the rest of the energy is advected into the star. Subject headings: accretion, accretion disks binaries: symbiotic stars: individual (AX Persei, CI Cygni)
|Main Author:||Godon, Patrick.|