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Solar-like Oscillations in Low-luminosity Red Giants: First Results from Kepler

Timothy R. Bedding 1 Daniel Huber 1 Dennis Stello 1 yvonne P. Elsworth 2 Saskia Hekker 2 T. Kallinger Savita Mathur 3, 4 Benoît Mosser 5 H. L. Preston Jérôme Ballot 6 Caroline Barban 5, 7 A. M. Broomhall D. L. Buzasi William J. Chaplin 2 Rafael A. García 3, 7 M. Gruberbauer S. J. Hale J. de Ridder Søren Frandsen 8 William J. Borucki 9 Timothy M. Brown 10 Jørgen Christensen-Dalsgaard 8 Ronald L. Gilliland 11 Jon M. Jenkins 9 Hans Kjeldsen 8 David Koch 9 Kevin Belkacem 12 L. Bildsten Hans Bruntt 1, 7 Tiago L. Campante 8, 13 Sébastien Deheuvels 5 A. Derekas M.-A. Dupret Marie-Jo Goupil 5 A. Hatzes G. Houdek M. J. Ireland C. Jiang Christoffer Karoff 2, 8 L. L. Kiss 14 yveline Lebreton 15 Andrea Miglio 12 Josefina Montalbán 12 Arlette Noels 12 Ian W. Roxburgh 16 Vinothini Sangaralingam 2 Ian R. Stevens 2 M. D. Suran N. J. Tarrant Achim Weiss 17 
Abstract : 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 (Δν) and the frequency of maximum power (νmax). We focus on a sample of 50 low-luminosity stars (νmax > 100 μHz, L <~ 30 L sun) 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 échelle 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 δν02 versus Δν. The small separation δν01 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.
Keywords : stars: oscillations
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Submitted on : Monday, January 16, 2012 - 2:22:38 PM
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Timothy R. Bedding, Daniel Huber, Dennis Stello, yvonne P. Elsworth, Saskia Hekker, et al.. Solar-like Oscillations in Low-luminosity Red Giants: First Results from Kepler. The Astrophysical Journal, American Astronomical Society, 2010, 713 (2), pp.L176-L181. ⟨10.1088/2041-8205/713/2/L176⟩. ⟨hal-00660340⟩

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