期刊
ASTRONOMY & ASTROPHYSICS
卷 470, 期 1, 页码 239-247出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361:20066615
关键词
stars : emission-line, Be; stars : circumstellar matter; line : formation; polarization
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 h greater than or similar to 0.5R(o) and particle density distribution laws N(R) = N-o(R-o/R)(n) with n less than or similar to 1 at R less than or similar to 3R(o) (R-o is the stellar radius; N-o is the particle density at R = R-o). Multi-scattering Monte Carlo simulations show that CD with particle density distributions N similar to R-n, where n depends on the distance R and n similar to 0.5 near the star, might account for the near-UV spectroplorarimetry of Be stars. CD with enhanced scale heights could explain the [H alpha, E(J - L)] correlation as they may produce about the same Ha 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.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据