Internal rapid rotation and its implications for stellar structure and pulsations

Abstract

Abstract. Massive and intermediate mass stars play a crucial role in astrophysics. Indeed, massive stars are the main producers of heavy elements, explode in supernovae at the end of their short lifetimes, and may be the progenitors of gamma ray bursts. Intermediate mass stars, although not destined to explode in supernovae, display similar phenomena, are much more numerous, and have some of the richest pulsation spectra. A key to understanding these stars is understanding the effects of rapid rotation on their structure and evolution. These effects include centrifugal deformation and gravity darkening which can be observed immediately, and long terms effects such as rotational mixing due to shear turbulence, which prolong stellar lifetime, modify chemical yields, and impact the stellar remnant at the end of their lifetime. In order to understand these effects, a number of models have been and are being developed over the past few years. These models lead to increasingly sophisticated predictions which need to be tested through observations. A particularly promising source of constraints is seismic observations as these may potentially lead to detailed information on their internal structure. However, before extracting such information, a number of theoretical and observational hurdles need to be overcome, not least of which is mode identification. The present proceedings describe recent progress in modelling these stars and show how an improved understanding of their pulsations, namely frequency patterns, mode visibilities, line profile variations, and mode excitation, may help with deciphering seismic observations.

BCD Spectrophotometry and Rotation of Active B-Type Stars: Theory and Observations

“…Improved methods to infer the internal rotation of stars based on asteroseismic measurements were developed since then [548]. Their application revealed internal differential rotation and put constraints on the internal rotation of some main-sequence B stars, e.g., [549][550][551][552].…”

Non-adiabatic pulsations in ESTER models

“…A look at the work integrals shows that modes are being stabilised by the very near surface layers, starting with the retrograde modes (see Fig. 2 of [25]). Different types of modes are excited.…”

Asymptotic theory of gravity modes in rotating stars

“…As compared to the wealth of new information obtained from the seismology of solar-type and red-giant stars (Miglio 2015), reliable seismic diagnostics on non-evolved, intermediate-mass and massive pulsators (γ Doradus, δ Scuti, β Cephei, SPB or Be stars) are scarce and, in any case, restricted to atypical slowly rotating stars (Kurtz et al 2014;Saio et al 2015;Triana et al 2015). This stems from our limited understanding of the effects of rotation on oscillation modes (Lignières 2013;Townsend 2014;Reese 2015), at least for the high rotation rates of typical non-evolved, intermediate-mass and massive stars (Royer et al 2007;Lignières 2013). The two classical approximations to treat rotational effects have been the perturbative expansion in Ω/ω, where Ω is the rotation rate and ω is the pulsation frequency (Saio 1981), and the so-called traditional approximation of the Coriolis acceleration (Eckart 1960).…”