Asteroseismology of 16,000 Kepler Red Giants: Global Oscillation Parameters, Masses, and Radii

Abstract

The Kepler mission has provided exquisite data to perform an ensemble asteroseismic analysis on evolved stars. In this work we systematically characterize solar-like oscillations and granulation for 16,094 oscillating red giants, using end-of-mission long-cadence data. We produced a homogeneous catalog of the frequency of maximum power (typical uncertainty σ νmax =1.6%), the mean large frequency separation (σ ∆ν =0.6%), oscillation amplitude (σ A =4.7%), granulation power (σ gran =8.6%), power excess width (σ width =8.8%), seismically derived stellar mass (σ M =7.8%), radius (σ R =2.9%), and thus surface gravity (σ log g =0.01 dex). Thanks to the large red giant sample, we confirm that redgiant-branch (RGB) and helium-core-burning (HeB) stars collectively differ in the distribution of oscillation amplitude, granulation power, and width of power excess, which is mainly due to the mass difference. The distribution of oscillation amplitudes shows an extremely sharp upper edge at fixed ν max , which might hold clues for understanding the excitation and damping mechanisms of the oscillation modes. We find that both oscillation amplitude and granulation power depend on metallicity, causing a spread of 15% in oscillation amplitudes and a spread of 25% in granulation power from [Fe/H]=-0.7 to 0.5 dex. Our asteroseismic stellar properties can be used as reliable distance indicators and age proxies for mapping and dating galactic stellar populations observed by Kepler . They will also provide an excellent opportunity to test asteroseismology using Gaia parallaxes, and lift degeneracies in deriving atmospheric parameters in large spectroscopic surveys such as APOGEE and LAMOST.

Giant Planet Occurrence within 0.2 au of Low-luminosity Red Giant Branch Stars with K2

“…We note the low frequency harmonic of this feature at ≈ 39 µHz, but do not mask this feature as stars with similar ν max values reside in the red clump or are too large to allow planet transit detection. In addition, we reject stars whose ν max and ∆ν values disagree with the empirical relation derived by Yu et al (2018) (given in the following paragraph) by more than 20%. This leaves us with a vetted asteroseismic sample of 5227 oscillating stars (red points in Figure 2).…”

“…The right panel gives the correlation between maximum oscillation amplitude and ν max for all stars in our target sample. We highlight the Yu et al (2018) relation determined between ν max and ∆ν from a sample of 16094 Kepler red giants,…”

ROBO-AO Kepler Asteroseismic Survey. II. Do Stellar Companions Inhibit Stellar Oscillations?

“…This lack of oscillations could suggest a significant physical difference between stars sharing similar fun- Figure 1. The amplitude of oscillations versus frequency of maximum power for the red giants in our sample (colored circles) and the red giants in Yu et al (2018) (light blue dots). The black line shows a linear fit whilst the gray lines correspond to 1, 2 and 3σ limits (each of these limits is quantified in the bottom left of the plot).…”

Variability in the Massive Open Cluster NGC 1817 from K2: A Rich Population of Asteroseismic Red Clump, Eclipsing Binary, and Main-sequence Pulsating Stars

“…If the masses of these faint clump stars can be determined precisely, the observations will put strong constraints on the main sequence stars that later produce minimum-mass helium cores. For the Kepler field-star sample, Yu et al (2018) used the asteroseismic scaling relations with red clump star corrections to ∆ν (Sharma et al 2016) to calculate stellar masses and radii. These are shown in Figure 12, and the radii show several expected features like the sharp primary/secondary clump (RC1/RC2) transition near 2.05M and the minimum radius among the RC2 stars around 8R .…”