Issue |
A&A
Volume 440, Number 1, September II 2005
|
|
---|---|---|
Page(s) | 305 - 320 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20042229 | |
Published online | 19 August 2005 |
Effects of gravitational darkening on the determination of fundamental parameters in fast-rotating B-type stars
1
Royal Observatory of Belgium, 3 avenue circulaire, 1180 Bruxelles, Belgium e-mail: yves.fremat@oma.be
2
Institut d'Astrophysique de Paris, CNRS, 98bis Boulevard Arago, 75014 Paris, France
3
Observatoire de Paris, Section d'Astrophysique de Meudon, GEPI, FRE K 2459, 5 place Jules Janssen, 92195 Meudon Cedex, France
Received:
22
October
2004
Accepted:
19
March
2005
In this paper we develop a calculation code to account
for the effects carried by fast rotation on the observed spectra
of early-type stars. Stars are assumed to be in rigid rotation,
and the grid of plane-parallel model atmospheres used to represent
the gravitational darkening are calculated by means of a non-LTE
approach. Attention is paid to the relation between the apparent and parent non-rotating counterpart stellar
fundamental parameters and apparent, and true parameters
as a function of the rotation rate
,
stellar mass, and inclination angle. It is shown that omitting of
gravitational darkening in the analysis of chemical abundances of
CNO elements can produce systematic overestimation or
underestimation, depending on the lines used, rotational rate, and
inclination angle. The proximity of Be stars to the critical
rotation is revised while correcting not only the
of 130
Be stars, but also their effective temperature and gravity to
account for stellar rotationally induced geometrical distortion
and for the concomitant gravitational darkening effect. We
concluded that the
increase is accompanied by an even
higher value for the stellar equatorial critical velocity, so that
the most probable average rate of the angular velocity of Be stars
attains
.
Key words: stars: abundances / stars: atmospheres / stars: early-type / stars: emission-line, Be / stars: fundamental parameters
© ESO, 2005
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