Properties of oscillation modes in subgiant stars observed by Kepler

TL;DR

This paper introduces a method to analyze oscillation modes in subgiant stars observed by Kepler, providing insights into their internal structure and properties through detailed mode characterization.

Contribution

It presents a novel approach to identify and measure all oscillation mode characteristics in subgiants, including the first measurement of the effect of mode mixing degree.

Findings

Measured the effect of mode mixing on l=1 mixed modes.

Detected measurable l=2 mixed modes in some stars.

Provided new constraints on stellar internal structure.

Abstract

Mixed modes seen in evolved stars carry information on their deeper layers that can place stringent constraints on their physics and on their global properties (mass, age, etc...). In this study, we present a method to identify and measure all oscillatory mode characteristics (frequency, height, width). Analyzing four subgiants stars, we present the first measure of the effect of the degree of mixture on the l=1 mixed modes characteristics. We also show that some stars have measurable l=2 mixed modes and discuss the interest of their measure to constrain the deeper layers of stars.