EDP Sciences
Free access
Volume 441, Number 1, October I 2005
Page(s) 235 - 248
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20053051

A&A 441, 235-248 (2005)
DOI: 10.1051/0004-6361:20053051

On the evolutionary status of Be stars

I. Field Be stars near the Sun
J. Zorec1, Y. Frémat2 and L. Cidale3, 4

1  Institut d'Astrophysique de Paris, UMR 7095 CNRS-Université Pierre & Marie-Curie, 98bis Bd. Arago, 75014 Paris, France
    e-mail: zorec@iap.fr
2  Royal Observatory of Belgium, 3 Av. Circulaire, 1180 Bruxelles, Belgium
3  Facultad de Ciencias Astronómicas y Geofísicas, Universidad de La Plata, Paseo del Bosque S/N, 1900 La Plata, Argentina
4  Instituto de Astrofísica La Plata, CONICET, 1900 La Plata, Argentina

(Received 11 March 2005 / Accepted 26 May 2005)

A sample of 97 galactic field Be stars were studied by taking into account the effects induced by the fast rotation on their fundamental parameters. All program stars were observed in the BCD spectrophotometric system in order to minimize the perturbations produced by the circumstellar environment on the spectral photospheric signatures. This is one of the first attempts at determining stellar masses and ages by simultaneously using model atmospheres and evolutionary tracks, both calculated for rotating objects. The stellar ages ($\tau$) normalized to the respective inferred time that each rotating star can spend in the main sequence phase ( $\tau_{\rm MS}$) reveal a mass-dependent trend. This trend shows that: a) there are Be stars spread over the whole interval $0 \la \tau/\tau_{\rm MS} \la 1$ of the main sequence evolutionary phase; b) the distribution of points in the ( $\tau/\tau_{\rm
MS},M/M_{\odot}$) diagram indicates that in massive stars ( $M \ga 12~M_{\odot}$) the Be phenomenon is present at smaller $\tau/\tau_{\rm MS}$ age ratios than for less massive stars ( $M \la 12~M_{\odot}$). This distribution can be due to: i) higher mass-loss rates in massive objets, which can act to reduce the surface fast rotation; ii) circulation time scales to transport angular momentum from the core to the surface, which are longer the lower the stellar mass.

Key words: stars: emission-line, Be  -- stars: evolution -- stars: rotation -- stars: fundamental parameters (classification, colors, luminosities, masses, radii, temperatures, etc.)

SIMBAD Objects

© ESO 2005

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.