Detection of solar-like oscillations in the G5 subgiant mu-Herculis

TL;DR

This paper reports the detection of solar-like oscillations in the G5 subgiant mu-Herculis, using high-precision spectroscopic observations, and identifies oscillation modes consistent with theoretical models.

Contribution

First detection of solar-like oscillations in mu-Herculis with detailed mode identification and comparison to theoretical expectations.

Findings

Detected excess power at 1.2 mHz with peak amplitudes of 0.9 m/s.

Identified oscillation modes with a large separation of 56.5 μHz.

Oscillation amplitudes are nearly three times solar values.

Abstract

A clear detection of excess of power, providing a substantial evidence for solar-like oscillations in the G5 subgiant \muher{}, is presented. This star was observed over seven nights with the SARG echelle spectrograph operating with the 3.6-m Italian TNG Telescope, using an iodine absorption cell as a velocity reference. A clear excess of power centered at 1.2 mHz, with peak amplitudes of about 0.9 \ms in the amplitude spectrum is present. Fitting the asymptotic relation to the power spectrum, a mode identification for the $\ell=0,1,2,3$ modes in the frequency range $900-1600 \muHz$ is derived. The most likely value for the large separation turns out to be 56.5 \muHz, consistent with theoretical expectations. The mean amplitude per mode ($l=0,1$) at peak power results to be $0.63 \rm m s^{-1}$, almost three times larger than the solar one.