π Aquarii is another γ Cassiopeiae object⋆
Groupe d’Astrophysique des Hautes Énergies, STAR, Université de Liège, Quartier Agora (B5c, Institut d’Astrophysique et de Géophysique), Allée du 6 Août 19c, 4000 Sart Tilman, Liège, Belgium
Received: 9 May 2017
Accepted: 24 May 2017
The γ Cas category is a subgroup of Be stars displaying a strong, hard, and variable thermal X-ray emission. An XMM-Newton observation of π Aqr reveals spectral and temporal characteristics that clearly make this Be star another member of the γ Cas category. Furthermore, π Aqr is a binary but, contrary to γ Cas, the nature of the companion to the Be star is known; it is a non-degenerate (stellar) object and its small separation from the Be star does not leave much room for a putative compact object close to the Be disk. This renders the accretion scenario difficult to apply in this system, and, hence, this discovery favors a disk-related origin for the γ Cas phenomenon.
Key words: stars: early-type / stars: emission-line, Be / X-rays: stars / stars: individual:πAqr
© ESO, 2017