Model-independent determination of sharp features inside a star from its oscillation frequencies

TL;DR

This paper demonstrates a model-independent method to determine the locations of sharp internal features like the convective zone base and helium ionisation zone in stars using their oscillation frequencies, applied here to HD49933.

Contribution

It introduces a novel seismic analysis technique applied to a star other than the Sun, accurately estimating the depths of internal features from oscillation data.

Findings

Acoustic depths of the convective zone and HeII ionisation zone determined within 10% error.

Method results agree with existing seismic models of HD49933.

First application of this analysis to a non-solar star.

Abstract

It has been established earlier that sharp features like the base of the convective zone or the second helium ionisation zone inside a star give rise to sinusoidal oscillations in the frequencies of pulsation. The acoustic depth of such features can be estimated from this oscillatory signal in the frequencies. We apply this technique for the CoRoT frequencies of the solar-type star HD49933. This is the first time that such analysis has been done of seismic data for any star other than the Sun. We are able to determine the acoustic depth of both the base of the convective zone and the HeII ionisation zone of HD49933 within 10% error from the second differences of the frequencies. The locations of these layers using this technique is in agreement with the current seismic models of HD49933.