Non-linear pulsations of the helium stars

Hydrodynamic calculations of radial non-linear stellar oscillations of helium stars with masses of 1M solar mass are presented. The first series of models is characterized by effective temperatures from 6000 to 8000 K and luminosities from 3220 the solar luminosity to 2.03 x 104 the solar luminosity. The blue edge of the instability strip was found to correspond to effective temperatures ranging from 7200 to 7500 K for both the fundamental mode and first overtone. Application of the core mass-luminosity relation for the helium stars together with the pulsation constants obtained show that the bolometric luminosity of R CrB and RYSgr is in the range from 8000 the solar luminosity to 104 the solar luminosity. All the models of the second series characterized by effective temperatures from 8000 to 30 000 K and bolometric luminosity of 2.03 x 104 the solar luminosity were found to be unstable. (author)