Seismic detection of acoustic sharp features in the CoRoT target HD49933

TL;DR

This paper applies a seismic technique to determine the locations of sharp sound speed changes inside the star HD49933, successfully estimating the depths of the helium ionisation zone and the convective zone base, with results aligning with stellar models.

Contribution

It demonstrates the application of acoustic signal analysis to a solar-type star, providing new measurements of internal stellar layer depths.

Findings

Acoustic depth of helium ionisation zone: 794 seconds

Acoustic depth of convective zone base: 1855 seconds

Results are consistent with stellar models

Abstract

The technique of determining the acoustic location of layers of sharp changes in the sound speed inside a star from the oscillatory signal in its frequencies is applied on a solar-type star, the CoRoT target, HD49933. We are able to determine the acoustic depth of the second helium ionisation zone of HD49933 to be 794 +55/-68 seconds. The acoustic depth of the base of the convective zone is found to be 1855 +173/-412 seconds where the large error bars reflect the ambiguity in the result, which is difficult to determine with present precision on the frequencies because of the intrinsically weak nature of the signal. The positions of both these layers are consistent with those in a representative stellar model of HD49933.