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Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2018

Hot stars observed by XMM-Newton II. A survey of Oe and Be stars

Yael Naze
  • Fonction : Auteur
Christian Motch

Résumé

We perform a survey of Oe and Be stars in the X-ray range. To this aim, we cross-correlated XMM-Newton and Chandra catalogs of X-ray sources with a list of Be stars, finding 84 matches in total. Of these, 51 objects had enough counts for a spectral analysis. This paper provides the derived X-ray properties (X-ray luminosities, and whenever possible, hardness ratios, plasma temperatures, and variability assessment) of this largest ever sample of Oe and Be stars. The targets display a wide range in luminosity and hardness. In particular, the significant presence of very bright and hard sources is atypical for X-ray surveys of OB stars. Several types of sources are identified. A subset of stars display the typical characteristics of O-stars, magnetic OB stars, or pre-main-sequence (PMS) objects: their Be nature does not seem to play an important role. However, another subset comprises γ Cas analogs, which are responsible for the luminous and hard detections. Our sample contains seven known γ Cas analogs, but we also identify eight new γ Cas analogs and one γ Cas candidate. This nearly doubles the sample of such stars.Key words: stars: early-type / stars: emission-line Be / X-rays: stars / stars: individual: γ Cas* Based on observations collected with NASA missions Chandra and Swift as well as the ESA observatory XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).** All tables are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc. u-strasbg.fr/viz-bin/qcat?J/A+A/619/A148*** F.R.S.-FNRS Research Associate.

Dates et versions

hal-01880831 , version 1 (25-09-2018)

Identifiants

Citer

Yael Naze, Christian Motch. Hot stars observed by XMM-Newton II. A survey of Oe and Be stars. Astronomy and Astrophysics - A&A, 2018, 619, pp.A148. ⟨10.1051/0004-6361/201833842⟩. ⟨hal-01880831⟩
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