Dominique Ballereau

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

Aims. The Fe ii emission lines formed in the circumstellar envelopes (CE) of classical Be stars are studied in order to determine whether they are optically thin or optically thick. We also aim at deriving both average Fe ii line excitation temperatures and the extent of their formation region in the CE. Methods. We simultaneously observed several series of Fe ii emission lines in the

NEW LAMBDA BOOTIS STARS WITH A SHELL

\lambda\lambda4230{-}7712

A 10-h period revealed in optical spectra of the highly variable WN8 Wolf-Rayet star WR 123

A wavelength interval and the first members of the hydrogen Balmer series of 18 southern classical Be stars. The optical depth regime that controls the formation of the observed Fe ii lines and the physical parameters of their CE formation region were studied using the empirical self-aborption-curve (SAC) method. Results. Our calculations give an average value of

EVOLUTION OF THE CIRCUMSTELLAR SHELL OF PLEIONE (1981-94)

\tau_{\rm o}=2.4\pm0.9

High and intermediate-resolution spectroscopy of Be stars - An atlas of H

for the optical depth of the studied Fe ii lines, which implies that these lines are optically thick in the CE of Be stars. Qualitative indications that Fe ii emission lines should be formed in circumstellar regions close to the central star are inferred from the correlations between Fe ii emission line widths and

\gamma

V\sin i

, He I 4471 and Mg II 4481 lines

. The application of the SAC method to Fe ii emission lines confirms this result, which gives

Coordinated monitoring of the eccentric O-star binary Iota Orionis: optical spectroscopy and photometry

R_{\rm e}=2.0R_*\pm0.8

Period Analysis of the Radial Velocity in Pleione

for the extension of the line-forming region. The proximity of the line-forming region to the central star is also supported by the behavior of the source function of Fe ii lines, which rapidly decreases with radii. This prevents the lines from being formed over extended regions and/or far from the star. Finally, the correlations of the central depression in the Balmer emission lines with

Fe II emission lines in Be stars

V\sin i