# Seismic measurement of the locations of the base of convection zone and helium ionization zone for stars in the {\it Kepler} seismic LEGACY sample

## TL;DR

This study uses Kepler seismic data to precisely locate the base of the convection zone and helium ionization zone in 66 stars, revealing robust helium signatures useful for stellar property inference.

## Contribution

First comprehensive seismic analysis of the LEGACY sample to locate stellar internal glitches, especially helium ionization zones, using high-precision Kepler data.

## Key findings

- Helium ionization zone signatures are consistently detectable across all stars.
- Convection zone signatures are weak and challenging to identify in more massive stars.
- Helium glitch signatures can constrain helium abundance and ionization layer properties.

## Abstract

Acoustic glitches are regions inside a star where the sound speed or its derivatives change abruptly. These leave a small characteristic oscillatory signature in the stellar oscillation frequencies. With the precision achieved by {\it Kepler} seismic data, it is now possible to extract these small amplitude oscillatory signatures, and infer the locations of the glitches. We perform glitch analysis for all the 66 stars in the {\it Kepler} seismic LEGACY sample to derive the locations of the base of the envelope convection zone and the helium ionization zone. The signature from helium ionization zone is found to be robust for all stars in the sample, whereas the convection zone signature is found to be weak and problematic, particularly for relatively massive stars with large errorbars on the oscillation frequencies. We demonstrate that the helium glitch signature can be used to constrain the properties of the helium ionization layers and the helium abundance.