Asteroseismology of alpha Cen A. Evidence of rotational splitting

TL;DR

This study improves the understanding of alpha Cen A's internal structure by identifying 34 p modes and highlighting the significance of rotational splitting in seismic analysis, using high-precision radial-velocity data from HARPS.

Contribution

The paper provides a detailed seismic characterization of alpha Cen A, including the first identification of multiple p modes and the demonstration of rotational splitting effects.

Findings

Identified 34 p modes with specific angular degrees and frequencies.

Detected rotational splitting affecting mode frequencies and lifetimes.

Derived new small separation values considering rotation.

Abstract

Asteroseismology provides a unique tool for studying stellar interiors. Recently p modes have been detected on the bright solar-like star alpha Cen A thanks to high-precision radial-velocity measurements. However a better characterisation of these p modes is clearly needed to constrain theoretical models. We observed alpha Cen A during five nights using the HARPS spectrograph in order to improve our knowledge of the seismic properties of this star. We performed high-precision radial-velocity sequences and computed the acoustic spectrum of alpha Cen A. We identify 34 p modes with angular degree l=0-3 in the frequency range 1.8-2.9 mHz and amplitude range 13-48 cm/s, in agreement with previous seismic studies. We find an enhancement of the frequency scatter with the angular degree l that indicates, considering the high inclination axis of alpha Cen A, rotational splitting and explains the low values of previously suggested mode lifetimes. We also derive new values for the small separations that take the effect of rotational splitting into account . Our seismic study of alpha Cen A leads to a list of now well identified p-mode frequencies and shows the importance of taking the rotation into account in order to properly characterise the p modes even in quite short campaigns.