Asteroseismology of the β Cephei star ν Eridani: interpretation and applications of the oscillation spectrum

Abstract

The oscillation spectrum of ν Eri is the richest known for any variable of the β Cephei type. We interpret the spectrum in terms of normal mode excitation and construct seismic models of the star. The frequency data combined with data on mean colours set the upper limit on the extent of overshooting from the convective core. We use data on rotational splitting of two dipole (ℓ= 1) modes (g1 and p1) to infer properties of the internal rotation rate. Adopting a plausible hypothesis of nearly uniform rotation in the envelope and increasing rotation rate in the μ‐gradient zone, we find that the mean rotation rate in this zone is about three times faster than in the envelope. In our standard model only the modes in the middle part of the oscillation spectrum are unstable. To account for excitation of a possible high‐order g mode at ν= 0.43 cd−1 as well as p modes at ν > 6 cd−1 we have to invoke an overabundance of Fe in the driving zone.

Fast core rotation in red-giant stars as revealed by gravity-dominated mixed modes

“…Claims of non-rigid rotation in white dwarfs have also been discussed 21 . The low-luminosity red giants 22 discussed here are in the early phase of hydrogen-shell burning, and have a core-to-envelope rotation rate more than twice as high as those of the massive stars 19,20 . When these stars enter the subsequent phase of core-helium burning, we believe that the core will undergo a slight expansion and the envelope will shrink, leading to a surface rotation on the horizontal branch larger than that on the red-giant branch 1 .…”

“…So far, our understanding of the evolution of the angular momentum as a function of the evolutionary stage is still poor. Before this study, it was possible to deliver evidence of non-rigid rotation in only two corehydrogen-burning massive stars, for which the seismic analysis revealed a near-core rotation rate about three to five times faster than the envelope rotation rate 19,20 . Claims of non-rigid rotation in white dwarfs have also been discussed 21 .…”

Triennial Report (2012-2015): The Legacy Issue

“…At about the same time, large observing campaigns were organized for a number of selected stars that led to first determinations of the interior structure of some stars, including constraints on convective overshooting and differential interior rotation (e.g. Aerts et al 422 DIVISION G COMMISSION 27 2003, Pamyatnykh et al 2004. Thanks to analyses of large photometric surveys, over 200 galactic β Cephei stars are nowadays known (Pigulski & Pojmański 2008), several of them also showing SPB-type oscillations, i.e.…”

Asteroseismology of the β Cep star ν Eri: initial results

“…We used both the Liege and Warsaw-New Jersey stellar evolution and pulsation codes (described, e.g., by Thoul et al 2003 andPamyatnykh et al 1998, respectively) for this purpose. …”