A Theoretical Study of Acoustic Glitches in Low-Mass Main-Sequence Stars

Abstract

There are regions in stars, such as ionization zones and the interface between radiative and convective regions, that cause a localized sharp variation in the sound speed. These are known as "acoustic glitches". Acoustic glitches leave their signatures on the oscillation frequencies of stars, and hence these signature can be used as diagnostics of these regions. In particular, the signature of these glitches can be used as diagnostics of the position of the second helium ionization zone and that of the base of the envelope convection zone. With the help of stellar models we study the properties of these acoustic glitches in main-sequence stars. We find that the acoustic glitch due to the helium ionization zone does not correspond to the dip in the adiabatic index Γ_1 caused by the ionization of HeII, but to the peak in Γ_1 between the HeI and HeII ionization zones. We find that it is easiest to study the acoustic glitch due to the helium ionization zone in stars with masses in the range 0.9--1.2 M_\odot.

Accepted for publication in ApJ

References in corpus (6)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Asteroseismology of the solar analogs 16 Cyg A & B from Kepler observations
• An asteroseismic signature of helium ionization
• Asteroseismic estimate of helium abundance of a solar analog binary system
• Solar heavy element abundance: constraints from frequency separation ratios of low-degree p modes
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• Tidally perturbed pulsations in the pre-main sequence $\delta$ Scuti binary RS Cha
• On using dipolar modes to constrain the helium glitch in red-giant stars
• Properties of the ionisation glitch: I. Modelling the ionisation region
• Solar Cycle Related Changes in the Helium Ionization Zones of the Sun
• Near-Core Acoustic Glitches are Not Oscillatory: Consequences for Asteroseismic Probes of Convective Boundary Mixing
• Evolutionary and Observational Properties of Red Giant Acoustic Glitch Signatures
• Asteroseismology of low-mass stars: the balance between partial ionisation and Coulomb interactions
• Glitch analysis and asteroseismic modelling of subgiant $\mu$ Herculis: confirming and interpreting the ${\Gamma }_1$ peak as the helium glitch
• Advanced asteroseismic modelling: breaking the degeneracy between stellar mass and initial helium abundance