Expanding Envelopes of Stars

Grain Formation in the Expanding Envelopes of T Tauri Stars

The possibility of the nucleation in the expanding envelopes of T Tauri stars is investigated by using the nucleation theory by Becker and Doring. The nucleation time scale r,. in .the gas is investigated assuming that only graphite is condensable. The expansion time scale roxo of the gas ejected from a T Tauri star is calculated assuming that the gas flow is steady and spherically symmetric. T...

ALI in Rapidly Expanding Envelopes

We discuss the current implementation of the ALI method into our HYDrodynamical RAdiation (Hydra) code for rapidly expanding, low density envelopes commonly found in core collapse and thermonuclear supernovae, novae and WR stars. Due to the low densities, non-thermal excitation by high energy photons (e.g. from radioactive decays) and the time dependence of the problem, significant departures f...

Imaging the circumstellar envelopes of AGB stars ⋆

Aims. We report the results of an exploratory program to image the extended circumstellar envelopes of asymptotic giant branch (AGB) stars in dust-scattered galactic light. The goal is to characterize the morphology of the envelopes as a probe of the mass-loss process. Methods. The observations consist of short exposures with the VLT and longer exposures with 1–2 m telescopes, augmented with ar...

Convective Envelopes in Solar - Type Stars :

Cooling Neutron Stars with Accreted Envelopes

Gilles Chabrier1, Alexander Y. Potekhin2;1;3, and Dmitry G. Yakovlev2 ABSTRACT The relationships between the e ective surface temperature Te and internal temperature Tb of nonmagnetized neutron stars with and without accreted envelopes are calculated for Te > 5 104 K. We use updated equations of state and radiative opacities, and we improve considerably the electron conductive opacity. We exami...