Massive pulsating stars observed by BRITE-Constellation: I. The triple system β Centauri (Agena)

Asteroseismology of massive pulsating stars of beta Cep and SPB types can help us to uncover the internal structure of massive stars and understand certain physical phenomena that are taking place in their interiors. We study beta Centauri (Agena), a triple system with two massive fast-rotating early B-type components which show p- and g-mode pulsations; the system's secondary is also known to have a measurable magnetic field. This paper aims to precisely determine the masses and detect pulsation modes in the two massive components of beta Cen with BRITE-Constellation photometry. Theoretically-predicted frequencies are calculated for the appropriate evolutionary models and their stability is checked. The effects of rotational splitting and coupling are also presented. Agena seems to be one of very few rapidly rotating massive objects with rich p- and g-mode spectra, and precisely known masses. Finally, the case studied here illustrates the potential of BRITE-Constellation data for the detection of rich-frequency spectra of small-amplitude modes in massive pulsating stars.