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arXiv · 1907.01338

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

A. Bonanno·E. Corsaro·F. Del Sordo·P. L. Pallé·D. Stello·M. Hon
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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.

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A. Bonanno, E. Corsaro, F. Del Sordo, P. L. Pallé, D. Stello, M. Hon. 2019-07-02. Acoustic oscillations and dynamo action in the G8 sub-giant EK Eri. https://doi.org/10.1051/0004-6361/201935834

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