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Investigation of oscillations above the acoustic cut-off frequency for a sample of Kepler stars. I. Methodology for detecting stellar pseudo-modes

L. J. Millson, A.-M. Broomhall, A. R. G. Santos, R. Kiefer

Abstract

Stellar oscillations with frequencies below the acoustic cut-off frequency are confined within resonant cavities in the stellar interior. However, waves with frequencies above the cut-off are not trapped, and are free to propagate into the stellar atmosphere. In solar power spectra, this is observed as a regular, repeating peak-like structure. Known as pseudo-modes, few previous studies have identified and analysed their nature in stars other than our Sun. In this work, we aimed to identify the presence of the pseudo-modes in a sample of 91 kepler stars, comprised mainly of the LEGACY sample and KOIs. To determine whether any statistically significant signal existed within the pseudo-modes, we utilised the power spectrum of the power spectrum (PSxPS) method. We generated a PSxPS for each star for a range of frequencies over which we expected to observe the pseudo-modes. Bootstrapping was then used to calculate the false alarm probability (FAP) for the peak at maximum PSxPS power. The presence of pseudo-modes was detected in 51 stars, which displayed a statistically significant peak  ( < 5 per cent FAP) in the PSxPS. Over half had a peak at maximum power greater than the < 1 per cent FAP level. We further examined the frequency of maximum PSxPS power, finding most stars had a frequency between one and one-half of the large frequency separation. Stars which showed evidence for a secondary significant ( < 5 per cent FAP) peak in the PSxPS were also recorded, and 19 stars were identified. The detection and characterisation of pseudo-modes may provide new insights into stellar magnetism. in a old version of tinymce is causing issues any idea why?

Keywords
stars: activity / stars: oscillations / stars: solar-type

Monthly Notices of the Royal Astronomical Society
Volume 536, Issue 3, Page 3007
2025 January

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia