The Envelopes of BE 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...

Rates of Energy Gain and Loss in the Circumstellar Envelopes of Be Stars: Diiuse Radiation

We have determined an upper limit to the kinetic temperature of the gas in the circumstellar envelopes of 2 Be stars, a hot star Cas, and a cooler star 1 Del, by including in an approximate manner the diiuse radiation produced in the envelope. We computed the temperature as a function of position by balancing at each position the rates of energy gain and energy loss. Photoionization, collisiona...

CONSTRAINTS ON THE GEOMETRY OF CIRCUMSTELLAR ENVELOPES: OPTICAL INTERFEROMETRIC AND SPECTROPOLARIMETRIC OBSERVATIONS OF SEVEN Be STARS

We have obtained contemporaneous optical interferometry and spectropolarimetry of seven Be stars. The interferometry was done using both continuum and narrow Ha line Ðlters to observe the circumstellar envelope emission. The envelopes of all seven stars were resolved interferometrically in Ha. Of these seven stars, the envelopes of four were not circularly symmetric and showed clear evidence of...

Rates of Energy Gain and Loss in the Circumstellar Envelopes of Be Stars: 1 Delphini

We have investigated the rates of energy gain and loss in the circum-stellar envelope of the cool B8-9e star, 1 Delphini , using the Poeckert-Marlborough model. We determined iteratively the kinetic temperature of the gas as a function of position in the circumstellar envelope by adjusting the temperature at each grid point until the rates of energy gain and loss there were equal. The gas was a...

Convective Envelopes in Solar - Type Stars :