Low-amplitude Solar-like Oscillations in the K5 V Star ϵ Indi A
M. Lundkvist, H. Kjeldsen, T. R. Bedding, M. J. McCaughrean, R. Paul Butler, D. Slumstrup, T. L. Campante, C. Aerts, T. Arentoft, H. Bruntt, C. Cardoso, F. Carrier, Laird M. Close, J. Gomes da Silva, T. Kallinger, Robert R. King, Yaguang Li, Simon J. Murphy, Jakob Rørsted Mosumgaard, Dennis Stello
Abstract
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 μ Hz—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.