# Acoustic oscillations and dynamo action in the G8 sub-giant EK Eri

## TL;DR

This study confirms acoustic oscillations in the G8 sub-giant EK Eri, analyzes their properties, and explores the star's magnetic field origin, with implications for stellar dynamo theories.

## Contribution

It provides new observational evidence of acoustic oscillations in EK Eri and proposes a novel amplitude-luminosity relation to explain missing power in the spectrum.

## Key findings

- Detected significant power excess at 253 μHz in the first observation
- Determined the large separation Δν = 16.43 μHz
- Proposed a new amplitude-luminosity relation for oscillation power

## Abstract

We present further evidence of the presence of acoustic oscillations on the slowly-rotating, over-active G8 sub-giant EK Eri. This star was observed with the 1-m Hertzsprung SONG telescope, at the Observatorio del Teide for two different runs of 8 and 13 nights, respectively, and separated by about a year. We determined a significant excess of power around $\nu_\mathrm{max} = 253 \pm 3\,\mu$Hz in the first observing run and we were able to determine the large separation $\Delta\nu = 16.43 \pm 0.22\,\mu$Hz. No significant excess of power was instead detected in a subsequent SONG observing season, as also supported by our analysis of the simultaneous TESS photometric observations. We propose a new amplitude-luminosity relation in order to account for the missing power in the power spectrum. Based on the evolutionary stage of this object we argue that standard $\alpha^2\Omega$ dynamo cannot be excluded as a possible origin for the observed magnetic field.