Issue |
A&A
Volume 470, Number 1, July IV 2007
|
|
---|---|---|
Page(s) | 239 - 247 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20066615 | |
Published online | 10 May 2007 |
Be star disc characteristics near the central object
1
Institut d'Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis bd. Arago, 75014 Paris, France e-mail: zorec@iap.fr
2
Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque sn, (1900) La Plata, Argentina
3
Instituto de Astrofísica de La Plata (CONICET-UNLP), Paseo del Bosque sn, (1900) La Plata, Argentina
Received:
21
October
2006
Accepted:
13
April
2007
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 and
particle density distribution laws
with
at
(Ro is the stellar radius; No is the particle density
at
). Multi-scattering Monte Carlo simulations show that CD with
particle density distributions
, where n depends on the
distance R and
near the star, might account for the near-UV
spectroplorarimetry of Be stars. CD with enhanced scale heights could explain
the [ Hα,
] correlation as they may produce about the same
Hα line emission, but larger IR flux excesses than thin discs. The
enlarged CD scale heights do not contradict the existing interferometric
measurements and should enable us to treat more consistently Balmer line
emission formation in Be stars.
Key words: stars: emission-line, Be / stars: circumstellar matter / line: formation / polarization
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.