Rapid Rotation and Nonradial Pulsations: Kappa-Mechanism Excitation of G-Modes in B Stars

Abstract

Several classes of stars (most notably O and B main-sequence stars, as well as accreting white dwarfs and neutron stars) rotate quite rapidly, at spin frequencies greater than the typical g-mode frequencies. We discuss how rapid rotation modifies the $\kappa$-mechanism excitation and observability of g-mode oscillations. We find that, by affecting the timescale match between the mode period and the thermal time at the driving zone, rapid rotation stabilizes some of the g-modes that are excited in a non-rotating star, and, conversely, excites g-modes that are damped in absence of rotation. The fluid velocities and temperature perturbations are strongly concentrated near the equator for most g-modes in rapidly rotating stars, which means that a favorable viewing angle may be required to observe the pulsations. Moreover, the stability of modes of the same $l$ but different $m$ is affected differently by rotation. We illustrate this by considering g-modes in Slowly Pulsating B-type stars as a function of the rotation rate.

7 pages, including 3 figures; uses emulateapj.sty (included); accepted to ApJ Letters

Cited by in corpus (10)

• Influence of the Coriolis force on the instability of slowly pulsating B stars
• The Long Term Stability of Oscillations During Thermonuclear X-ray Bursts: Constraining the Binary X-ray Mass Function
• Massive pulsating stars observed by BRITE-Constellation. I. The triple system Beta Centauri (Agena)
• Stellar variability in open clusters. I. A new class of variable stars in NGC 3766
• Hydrogen Electron Capture in Accreting Neutron Stars and the Resulting g-Mode Oscillation Spectrum
• Unstable quasi g-modes in rotating main-sequence stars
• R modes of slowly pulsating B stars
• Stellar variability in open clusters. II. Discovery of a new period-luminosity relation in a class of fast-rotating pulsating stars in NGC 3766
• Non-linear Three-mode Coupling of Gravity Modes in Rotating Slowly Pulsating B Stars: Stationary Solutions and Modeling Potential
• On the new late B- and early A-type periodic variable stars