Low-amplitude Solar-like Oscillations in the K5 V Star ϵ Indi A
Butler, R. Paul; Li, Yaguang; Bedding, Timothy R.; Stello, Dennis; Aerts, Conny; Murphy, Simon J.; Campante, Tiago L.; Kjeldsen, Hans; Kallinger, Thomas; Lundkvist, Mia S.; Close, Laird M.; Gomes da Silva, João; McCaughrean, Mark J.; Slumstrup, Ditte; King, Robert R.; Arentoft, Torben; Bruntt, Hans; Cardoso, Cátia V.; Carrier, Fabien; Rørsted, Jakob L.
Denmark, Australia, Netherlands, United States, Chile, Portugal, Belgium, Austria, United Kingdom
Abstract
We have detected solar-like oscillations in the mid-K-dwarf ϵ Indi A, making it the coolest dwarf to have measured oscillations. The star is noteworthy for harboring a pair of brown dwarf companions and a Jupiter-type planet. We observed ϵ Indi A during two radial velocity campaigns, using the high-resolution spectrographs HARPS (2011) and UVES (2021). Weighting the time series, we computed the power spectra and established the detection of solar-like oscillations with a power excess located at 5265 ± 110 μHz—the highest frequency solar-like oscillations so far measured in any star. The measurement of the center of the power excess allows us to compute a stellar mass of 0.782 ± 0.023 M ⊙ based on scaling relations and a known radius from interferometry. We also determine the amplitude of the peak power and note that there is a slight difference between the two observing campaigns, indicating a varying activity level. Overall, this work confirms that low-amplitude solar-like oscillations can be detected in mid-K-type stars in radial velocity measurements obtained with high-precision spectrographs.