A Theoretical Study of the Outer Layers of Eight Kepler F-stars: The Relevance of Ionization Processes

Abstract

We have analyzed the theoretical model envelopes of eight Kepler F-stars by computing the phase shift of the acoustic waves, $\alpha (\omega )$, and its related function, $\beta (\omega )$. The latter is shown to be a powerful probe of the external stellar layers since it is particularly sensitive to the partial ionization zones located in these upper layers. We found that these theoretical envelopes can be organized into two groups, each of which is characterized by a distinct $\beta (\omega )$ shape that we show to reflect the differences related to the magnitudes of ionization processes. Since $\beta (\omega )$ can also be determined from the experimental frequencies, we compared our theoretical results with the observable $\beta (\omega )$. Using the function $\beta (\omega )$, and with the purpose of quantifying the magnitude of the ionization processes occurring in the outer layers of these stars, we define two indexes, $\Delta {\beta }_1$ and $\Delta {\beta }_2$. These indexes allow us to connect the microphysics of the interior of the star with macroscopic observable characteristics. Motivated by the distinct magnetic activity behaviors of F-stars, we studied the relation between the star's rotation period and these indexes. We found a trend, in the form of a power-law dependence, that favors the idea that ionization is acting as an underlying mechanism, which is crucial for understanding the relation between rotation and magnetism and even observational features such as the Kraft break.

arXiv comment16 pages, 9 figures, 2 tables, Accepted for publication in ApJ

References in corpus (45)

• The chemical composition of the Sun
• The SIMBAD astronomical database
• Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics
• The PLATO 2.0 Mission
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• Ages for illustrative field stars using gyrochronology: viability, limitations and errors
• Rotation Periods of 34,030 Kepler Main-Sequence Stars: The Full Autocorrelation Sample
• Asteroseismology of Solar-Type and Red-Giant Stars
• Kepler Asteroseismology Program: Introduction and First Results
• Weakened magnetic braking as the origin of anomalously rapid rotation in old field stars
• ADIPLS -- the Aarhus adiabatic oscillation package
• Fundamental Properties of Kepler Planet-Candidate Host Stars using Asteroseismology
• Ensemble Asteroseismology of Solar-Type Stars with the NASA Kepler Mission
• Calculating asteroseismic diagrams for solar-like oscillations
• Standing on the shoulders of Dwarfs: the $Kepler$ asteroseismic LEGACY sample I - oscillation mode parameters
• CoRoT reveals a magnetic activity cycle in a Sun-like star
• Accurate parameters of 93 solar-type Kepler targets
• Fast Star, Slow Star; Old Star, Young Star: Subgiant Rotation as a Population and Stellar Physics Diagnostic
• Calibrating Gyrochronology using Kepler Asteroseismic targets
• A uniform asteroseismic analysis of 22 solar-type stars observed by Kepler
• Verifying asteroseismically determined parameters of Kepler stars using hipparcos parallaxes: self-consistent stellar properties and distances
• Magnetic activity of F stars observed by Kepler
• Oscillation mode frequencies of 61 main sequence and subgiant stars observed by Kepler
• How Good a Clock is Rotation? The Stellar Rotation-Mass-Age Relationship for Old Field Stars
• Asymptotic and measured large frequency separations
• An asteroseismic signature of helium ionization
• Stellar Evidence that the Solar Dynamo may be in Transition
• The Color-Period Diagram and Stellar Rotational Evolution - New Rotation Period Measurements in the Open Cluster M34
• Nearly-uniform internal rotation of solar-like main-sequence stars revealed by space-based asteroseismology and spectroscopic measurements
• Correcting the spectroscopic surface gravity using transits and asteroseismology. No significant effect on temperatures or metallicities with ARES+MOOG in LTE
• Measurement of acoustic glitches in solar-type stars from oscillation frequencies observed by Kepler
• Asteroseismic determination of helium abundance in stellar envelopes
• The Solar-Stellar Connection
• Asteroseismic estimate of helium abundance of a solar analog binary system
• Asteroseismic diagrams from a survey of solar-like oscillations with Kepler
• Stellar magnetic activity and variability of oscillation parameters - An investigation of 24 solar-like stars observed by Kepler
• Solving the mode identification problem in asteroseismology of F stars observed with Kepler
• First asteroseismic limits on the nature of dark matter
• Asteroseismic stellar activity relations
• Solar cycle variations of large frequency separations of acoustic modes: Implications for asteroseismology
• Asteroseismic signatures of helium gradients in late F-type stars
• Local perturbations of the upper layers of a Sun-like star: the impact on the acoustic oscillation spectrum
• Sounding the Solar Cycle with Helioseismology: Implications for Asteroseismology
• The CoRoT target HD49933: a possible seismic signature of heavy elements ionization in the deep convective zone
• Seismic signature of helium ionization in the Sun and stars

Cited by in corpus (3)

• The partial ionisation zone of heavy elements in F-stars: a study on how it correlates with rotation
• From cool to hot F-stars: the influence of two ionization regions in the acoustic oscillations
• Asteroseismology of low-mass stars: the balance between partial ionisation and Coulomb interactions