Adela E. Ringuelet

Dielectronic Recombination of Mg II in Stellar Envelopes

The aim of the present paper is to discuss the significance, in the infrared continuum of Be stars, of the dielectronic recombination (DR) of Mg II atoms. To accomplish this, we have calculated the emissivity in the lines of Mg I atoms after the process of electron capture has taken place. In order to estimate its influence in the photospheric flux, we have considered the total energy emitted in all lines with λ1 ≤ λ ≤ λ2, where λ1 and λ2 define the wavelength ranges of the Johnson system filters. We conclude that the DR of Mg II atoms does actually contribute significantly to the infrared excess observed in Be stars.

Be star disc characteristics near the central object

Context. A recent analysis of visual Fe ii emission lines of 17 classic Be stars using the self-absorption curve (SAC) method revealed that these lines are optically thick and that they form in circumstellar disc (CD) regions within two stellar radii from the central star on average. Aims. The aim of this paper is to study the physical characteristics of CD regions situated close to the central star. Methods. We used the Fe ii emission line optical depths derived for a sample of the above mentioned classic Be stars that are seen either nearly pole-on or equator-on. The disc properties sought are then inferred by reproducing the average pole-on and equator-on Fe ii line optical depths using simple CD models with different density and temperature distributions. Results. We found that the CD regions near the star, which account for the average Fe ii line opacities obtained with the SAC method, have semi-height scales perpendicular to the equatorial plane

Fe II emission lines in Be stars. I. Empirical diagnostic of physical conditions in the circumstellar discs

h\ga0.5R_{\rm o}

Rigorous treatment of the radiative transfer problem in stellar winds - Significance of the velocity law and the chromosphere in the H-alpha profile

and particle density distribution laws

Constraints on the Wind Structure of OB Stars from Theoretical He II Lines

N(R)=N_{\rm o}(R_{\rm o}/R)^{n}

Analysis of the velocity law in the wind of the Be star Lambda Pavonis

with

Expanding atmospheric model including a chromosphere. I: Study of the infrared excess in Be stars

n\la1

The extended atmosphere of Lambda Pavonis at the time of the emergence of H-emissions from minimum intensity

at

The circumstellar environment of the star V923 Aquilae

R\la3R_{\rm o}

Magnetohydrodynamic flows in Be stars : variable energy flux and heat input distribution

( R o is the stellar radius; N o is the particle density at