Domains of pulsational instability of low-frequency modes in rotating upper main sequence stars

Abstract

We determine instability domains on the Hertzsprung-Russel diagram for rotating main sequence stars with masses 2-20 M . The effects of the Coriolis force are treated in the framework of the traditional approximation. High-order g-modes with the harmonic degrees, , up to 4 and mixed gravity-Rossby modes with |m| up to 4 are considered. Including the effects of rotation results in wider instability strips for a given comparing to the non-rotating case and in an extension of the pulsational instability to hotter and more massive models. We present results for the fixed value of the initial rotation velocity as well as for the fixed ratio of the angular rotation frequency to its critical value. Moreover, we check how the initial hydrogen abundance, metallicity, overshooting from the convective core and the opacity data affect the pulsational instability domains. The effect of rotation on the period spacing is also discussed.

Probing the interior physics of stars through asteroseismology

“…These ranges are obtained when varying the mass (from 1.3M ⊙ to 2.0M ⊙ ), age, metallicity, and mixing properties of models in appropriate regimes according to the observed mode frequencies (Van Reeth, Tkachenko, and . Main-sequence B-type g-mode pulsators, on the other hand, reveal a much broader range covering roughly ΔP ∈ ½1000; 15 000 s (Pápics et al, 2017;Szewczuk and Daszyńska-Daszkiewicz, 2017). These stars have masses between 3M ⊙ and 10M ⊙ .…”

Asteroseismology of High-Mass Stars: New Insights of Stellar Interiors With Space Telescopes

“…From a more theoretical perspective, the distorted spherical symmetry of rapidly-rotating stars impacts the applicability of using 1D models, and because phenomena associated with rapid rotation, such as rotationally-induced mixing, can significantly influence evolutionary tracks in the HR diagram (Maeder and Meynet, 2000;Maeder, 2009;Lovekin, 2020). Moreover, as discussed in section 2.2.1, the Coriolis force perturbs the pulsation frequencies of a rotating star and consequently also the expected parameter range of instability regions in the HR diagram (Townsend, 2005;Bouabid et al, 2013;Szewczuk and Daszyńska-Daszkiewicz, 2017).…”

“…There are currently four known excitation mechanisms that can trigger variability in early-type stars: (i) coherent p and g modes excited by the κ-mechanism Gautschy and Saio, 1993;Szewczuk and Daszyńska-Daszkiewicz, 2017); (ii) IGWs generated by turbulent core convection (Edelmann et al, 2019); (iii) IGWs generated by thin sub-surface convection zones (Cantiello et al, 2009); and (iv) waves generated from tides in binary systems (Fuller, 2017). Whereas, essentially all of the asteroseismic results discussed in section 4 are based on heat-driven modes, the other variability mechanisms in massive stars remain somewhat under-utilized despite having great probing power of stellar interiors.…”

New β Cep pulsators discovered with K2 space photometry

“…The β Cep strip is sensitive to many parameters, i.e. metallicity, given that the modes are excited by a heat mechanism (Szewczuk & Daszyńska-Daszkiewicz 2017).…”