Moving inhomogeneous envelopes of stars

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...

Differential rotation decay in the radiative envelopes of CP stars

Stars of spectral classes A and late B are almost entirely radiative. CP stars are a slowly rotating subgroup of these stars. It is possible that they possessed long-lived accretion disks in their T Tauri phase. Magnetic coupling of disk and star leads to rotational braking at the surface of the star. Microscopic viscosities are extremely small and will not be able to reduce the rotation rate o...

Minimal models of cooling neutron stars with accreted envelopes

We study the ‘minimal’ cooling scenario of superfluid neutron stars with nucleon cores, where the direct Urca process is forbidden and enhanced cooling is produced by neutrino emission due to the Cooper pairing of neutrons. Extending our recent previous work, we include the effects of surface accreted envelopes of light elements. We employ the phenomenological density-dependent critical tempera...