Issue |
A&A
Volume 377, Number 1, October I 2001
|
|
---|---|---|
Page(s) | 113 - 122 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20011031 | |
Published online | 15 October 2001 |
Spectroscopic nonadiabatic observables
in
Cephei models
Astronomical Institute of the Wrocław University, ul. Kopernika 11, 51-622 Wrocław, Poland
Corresponding author: H. Cugier, cugier@astro.uni.wroc.pl
Received:
4
May
2001
Accepted:
11
July
2001
We calculate time sequences of Si III 455.26 nm line profiles
for 10 models using results of the linear
nonadiabatic calculations of Dziembowski & Pamyatnykh ([CITE]) for
oscillations of β Cephei stars. The spectroscopic observables are
amplitude ratios and phase differences for various oscillating
parameters derived from line profiles.
We search theoretical diagrams involving these observables
for unstable modes with low
harmonic degrees (
, 1 and 2) and azimuthal orders of
.
We show that all unstable modes are grouped in
domains assigned by different
and m-values.
In almost all studied diagrams, the
retrograde (
), prograde (
) and zonal (
) modes
are well separated from each other.
The clearest separation of the domains occurs for the
m-values in the diagram making use of the first and second moments
of line profiles. Neither the inclination angle i or the amplitude
of the stellar radius variation ϵ change this conclusion.
The diagram is however sensitive to the equatorial velocity ve
of the star. The method of determination of m is valid and
efficient for the equatorial rotational velocity
km
.
The observables studied here are usually by-products of periodogram
analyses of time series of observed characteristics of line profiles.
Our results point to the significance of such data for asteroseismology
in addition to measurements of oscillation frequencies and
photometric nonadiabatic observables.
Key words: stars: variables: general / stars: oscillations / stars: early-type
© ESO, 2001
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