First Results from the Hertzsprung SONG Telescope: Asteroseismology of the G5 Subgiant Star μ Herculis

Grundahl, F.; Fredslund Andersen, M.; Christensen-Dalsgaard, J.; Antoci, V.; Kjeldsen, H.; Handberg, R.; Houdek, G.; Bedding, T. R.; Pallé, P. L.; Jessen-Hansen, J.; Silva Aguirre, V.; White, T. R.; Frandsen, S.; Albrecht, S.; Andersen, M. I.; Arentoft, T.; Brogaard, K.; Chaplin, W. J.; Harpsøe, K.; Jørgensen, U. G.; Karovicova, I.; Karoff, C.; Kjærgaard Rasmussen, P.; Lund, M. N.; Sloth Lundkvist, M.Skottfelt, J.; Norup Sørensen, A.; Tronsgaard, R.; Weiss, E.

First Results from the Hertzsprung SONG Telescope: Asteroseismology of the G5 Subgiant Star μ Herculis,
The Astrophysical Journal, Vol. 836, Issue 1

Abstract

We report the first asteroseismic results obtained with the Hertzsprung Stellar Observations Network Group Telescope from an extensive high-precision radial-velocity observing campaign of the subgiant μ Herculis. The data set was collected during 215 nights in 2014 and 2015. We detected a total of 49 oscillation modes with l values from zero to three, including some l = 1 mixed modes. Based on the rotational splitting observed in l = 1 modes, we determine a rotational period of 52 days and a stellar inclination angle of 63°. The parameters obtained through modeling of the observed oscillation frequencies agree very well with independent observations and imply a stellar mass between 1.11 and 1.15 M  and an age of 7.8-0.4+0.3 Gyr. Furthermore, the high-quality data allowed us to determine the acoustic depths of the He ii ionization layer and the base of the convection zone.

Key words: asteroseismology / instrumentation: spectrographs / methods: data analysis / methods: observational / stars: individual: HD 161797 / stars: oscillations

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