EDP Sciences
Free access
Volume 507, Number 2, November IV 2009
Page(s) 1141 - 1201
Section Catalogs and data
DOI http://dx.doi.org/10.1051/0004-6361/200912304
Published online 03 September 2009
A&A 507, 1141-1201 (2009)
DOI: 10.1051/0004-6361/200912304

A systematic study of variability among OB-stars based on HIPPARCOS photometry

L. Lefèvre1, 2, S. V. Marchenko3, A. F. J. Moffat2, and A. Acker4

1  LESIA, CNRS UMR 8109, Observatoire de Paris, Université Paris 6, Université Paris 7, 92195 Meudon Cedex, France
    e-mail: laure.lefevre@obspm.fr
2  Département de Physique, Université de Montréal, Observatoire du Mont Mégantic, Centre de Recherche en Astrophysique du Québec, Montréal, QC H3C 3J7, Canada
    e-mail: [lefevre,moffat]@astro.umontreal.ca
3  Department of Physics and Astronomy, WKU, Bowling Green, KY 42101-3576, USA
    e-mail: sergey@astro.wku.edu
4  Observatoire de Strasbourg, 11 rue de l'Université, 67000 Strasbourg, France
    e-mail: acker@astro.u-strasbg.fr

Received 8 April 2009 / Accepted 6 August 2009

Context. Variability is a key factor for understanding the nature of the most massive stars, the OB stars. Such stars lie closest to the unstable upper limit of star formation.
Aims. In terms of statistics, the data from the HIPPARCOS satellite are unique because of time coverage and uniformity. They are ideal to study variability in this large, uniform sample of OB stars.
Methods. We used statistical techniques to determine an independant threshold of variability corresponding to our sample of OB stars, and then applied an automatic algorithm to search for periods in the data of stars that are located above this threshold. We separated the sample stars into 4 main categories of variability: 3 intrinsic and 1 extrinsic. The intrinsic categories are: OB main sequence stars (~2/3 of the sample), OBe stars (~10%) and OB Supergiant stars (~1/4).The extrinsic category refers to eclipsing binaries.
Results. We classified about 30% of the whole sample as variable, although the fraction depends on magnitude level due to instrumental limitations. OBe stars tend to be much more variable ($\approx$80%) than the average sample star, while OBMS stars are below average and OBSG stars are average. Types of variables include $\alpha$ Cyg, $\beta$ Cep, slowly pulsating stars and other types from the general catalog of variable stars. As for eclipsing binaries, there are relatively more contact than detached systems among the OBMS and OBe stars, and about equal numbers among OBSG stars.

Key words: methods: statistical -- methods: data analysis -- techniques: photometric -- catalogs -- stars: variables: general -- stars: fundamental parameters

© ESO 2009

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.