In:
Publications of the Astronomical Society of Japan, Oxford University Press (OUP), Vol. 60, No. 4 ( 2008-08-25), p. 749-769
Abstract:
The non-LTE state of the hydrogen gas in isothermal transonic decretion disks around a B1V star has been calculated by an iterative method in order to explore the basic physical process in the disk. This dynamical model is characterized by a density law in the equatorial plane of $\rho(R) \propto R^{-3.5}$. The continuous radiation was calculated with the $\Lambda$ iteration in the integral form, while we adopted a single-flight escape probability for lines. We describe the non-LTE state, the radiation flow and conversion in the disk. We conclude that the stellar Balmer continuum plays a key role in the non-LTE state of the disk. An examination of the local energy gain and loss suggests that the disk temperature has double minima along the equatorial plane in the optically thick case: the intermediate region caused by deficient ultraviolet radiation and the outer Lyman $\alpha$ cooling region. We also calculated some observable quantities, such as the spectral energy distribution, the $UBV$ colors, the infrared excess and the Balmer line profiles. Our calculations with a mass-loss rate less than $10^{-10}M_{\odot}\ {\rm yr}^{-1}$ reproduce the observed continuum quantities. However, we could not obtain the large H$\alpha$ emission strength observed in Be stars. We suggest that the density gradient of the Be star disk is slower than that of an isothermal decretion disk.
Type of Medium:
Online Resource
ISSN:
0004-6264
,
2053-051X
DOI:
10.1093/pasj/60.4.749
Language:
English
Publisher:
Oxford University Press (OUP)
Publication Date:
2008
detail.hit.zdb_id:
2206640-8
detail.hit.zdb_id:
2083084-1
SSG:
16,12
