Solar-Like Oscillations in Low-Luminosity Red Giants: First Results From Kepler
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Colleges, School and Institutes
We have measured solar-like oscillations in red giants using time-series photometry from the first 34 days of science operations of the Kepler Mission. The light curves, obtained with 30 minute sampling, reveal clear oscillations in a large sample of G and K giants, extending in luminosity from the red clump down to the bottom of the giant branch. We confirm a strong correlation between the large separation of the oscillations (Delta nu) and the frequency of maximum power (nu(max)). We focus on a sample of 50 low-luminosity stars (nu(max) > 100 mu Hz, L less than or similar to 30 L-circle dot) having high signal-to-noise ratios and showing the unambiguous signature of solar-like oscillations. These are H-shell-burning stars, whose oscillations should be valuable for testing models of stellar evolution and for constraining the star formation rate in the local disk. We use a new technique to compare stars on a single echelle diagram by scaling their frequencies and find well-defined ridges corresponding to radial and non-radial oscillations, including clear evidence for modes with angular degree l = 3. Measuring the small separation between l = 0 and l = 2 allows us to plot the so-called C-D diagram of delta nu(02) versus Delta nu. The small separation delta nu(01) of l = 1 from the midpoint of adjacent l = 0 modes is negative, contrary to the Sun and solar-type stars. The ridge for l = 1 is notably broadened, which we attribute to mixed modes, confirming theoretical predictions for low-luminosity giants. Overall, the results demonstrate the tremendous potential of Kepler data for asteroseismology of red giants.
|Journal||Astrophysical Journal Letters|
|Early online date||31 Mar 2010|
|Publication status||Published - 20 Apr 2010|
- stars: individual (KIC8410637), techniques: photometric, stars: fundamental parameters, stars: individual (Procyon A), stars: oscillations, binaries: eclipsing, methods: data analysis, stars: interiors, open clusters and associations: individual (NGC 6819)