Asteroseismology of 1523 misclassified red giants using $\text{Kepler}$ data

Abstract

We analysed solar-like oscillations in 1523 $\text{Kepler}$ red giants which have previously been misclassified as subgiants, with predicted ${\nu }_{\max }$ values (based on the Kepler Input Catalogue) between 280$\mu$Hz to 700$\mu$Hz. We report the discovery of 626 new oscillating red giants in our sample, in addition to 897 oscillators that were previously characterized by Hekker et al. (2011) from one quarter of $\text{Kepler}$ data. Our sample increases the known number of oscillating low-luminosity red giants by $26\%$ (up to $\sim$ 1900 stars). About three quarters of our sample are classified as ascending red-giant-branch stars, while the remainder are red-clump stars. A novel scheme was applied to determine $\Delta \nu$ for 108 stars with ${\nu }_{\max }$ close to the Nyquist frequency (240$\mu$Hz < ${\nu }_{\max }$ < 320$\mu$Hz). Additionally, we identified 47 stars oscillating in the super-Nyquist frequency regime, up to 387$\mu$Hz, using long-cadence light curves. We show that the misclassifications are most likely due to large uncertainties in KIC surface gravities, and do not result from the absence of broadband colors or from different physical properties such as reddening, spatial distribution, mass or metallicity. The sample will be valuable to study oscillations in low-luminosity red giants and to characterize planet candidates around those stars.

Accepted for publication in MNRAS, 12 pages, 12 figures, 1 table

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• A New Method for the Asteroseismic Determination of the Evolutionary State of Red-Giant Stars
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• A Search for Red Giant Solar-like Oscillations in All Kepler Data
• Six new rapidly oscillating Ap stars in the Kepler long-cadence data using super-Nyquist asteroseismology
• Clumpiness: Time-domain classification of red-giant evolutionary states
• A simple method to measure numax for asteroseismology: application to 16,000 oscillating Kepler red giants
• A Homogeneous Catalog of Oscillating Solar-Type Stars Observed by the Kepler Mission and a New Amplitude Scaling Relation Including Chromospheric Activity
• An Introduction to Data Analysis in Asteroseismology
• Beyond the Nyquist frequency: Asteroseismic catalog of undersampled Kepler late subgiants and early red giants
• Asteroseismology with TESS: Emergence of Dipole Mode Suppression From Subgiants?
• Hidden oscillations in plain sight: identification of seismically unresolved red-giant asteroseismic binary candidates