Accretion disc boundary layers around pre-main sequence stars.
One-dimensional time dependent calculations clf gco]nctrically thin accretion discs botindary layers in pre-main sequence st am arc carried out for mass accretion rates in the range M = 5 x 10-7 - 10' 4M0/y, a = 0.005- 0.3 and different inner boundary conditions on the temperature. '1'wo kinds of solutions arc obtained: solutions with a distinct the;rnal boundary layer coxnporlcnt and solution without~ermal boundary I! layer. For M up to N 10"-51vf0/y, and for a > crCritjC w 0.04, solutions with a thermal 111, arc obtained. l'or M = 10- 4M0/y or for a < ~critic, solutions without a thermal III, arc obtained. The inner boundary condition Fr = ~ Uljjj leads to hotter solutions and higher threshold values ~Criticj while the non-flux boundary condition dT/dr == O leads to cooler solutions. For very low mi~s accretion rate (M w 5 x 10-7 M0/y), the -tc~npcraturc in the disc drops Lclow 104K and tllc ionization front is adjacent to tlic outer edge of the hot thcrrnal boundary layer. III the vicinity of the ionization front, the medium bccc)mcs slightly optically thin.
|Main Author:||Godon, Patrick.|