A search of very low amplitude magnetoacoustic pulsations with HARPS

TL;DR

This study used the HARPS spectrograph to search for very low amplitude pulsations in cool Ap stars, confirming known pulsations in beta CrB and discovering new low-amplitude oscillations in HD 75445.

Contribution

First spectroscopic search for low-amplitude pulsations in Ap stars using HARPS, revealing new pulsation detections and characterizing their multiperiodic nature.

Findings

Confirmed 16-min pulsations in beta CrB

Discovered 9-min low-amplitude pulsations in HD 75445

Demonstrated multiperiodic oscillations in beta CrB

Abstract

We have obtained time-resolved spectroscopic observations for a sample of 10 cool Ap stars using the ultra-stable spectrograph HARPS at the ESO 3.6-m telescope. The aim of our study was to search for low-amplitude oscillations in Ap stars with no or inconclusive evidence of pulsational variability. Here we report initial results of our investigation. We confirm the presence of ~16-min period pulsations in beta CrB (HD 137909) and demonstrate multiperiodic character of oscillations in this star. Furthermore, we discovered very low amplitude 9-min pulsations in HD 75445 - an object spectroscopically very similar to known roAp stars.