A search for solar-like oscillations in the Am star HD 209625

TL;DR

This study searched for solar-like oscillations in the Am star HD 209625 using high-precision radial velocity measurements but found no significant oscillation signals, suggesting such oscillations are either absent or below detection thresholds.

Contribution

First observational search for solar-like oscillations in an Am star, testing models predicting near-surface convection zones in such stars.

Findings

No excess power in the star's power spectrum.

Oscillations, if present, are below 20-30 cm/s in amplitude.

Results constrain models of stellar surface convection in Am stars.

Abstract

The goal is to test the structure of hot metallic stars, and in particular the structure of a near-surface convection zone using asteroseismic measurements. Indeed, stellar models including a detailed treatement of the radiative diffusion predict the existence of a near-surface convection zone in order to correctly reproduce the anomalies in surface abundances that are observed in Am stars. The Am star HD 209625 was observed with the Harps spectrograph mounted on the 3.6-m telescope at the ESO La Silla Observatory (Chile) during 9 nights in August 2005. This observing run allowed us to collect 1243 radial velocity (RV) measurements, with a standard deviation of 1.35 m/s. The power spectrum associated with these RV measurements does not present any excess. Therefore, either the structure of the external layers of this star does not allow excitation of solar-like oscillations, or the amplitudes of the oscillations remain below 20-30 cm/s (depending on their frequency range).