Bayesian peak bagging analysis of 19 low-mass low-luminosity red giants observed with Kepler
Résumé
Context. Non-radial oscillations, observed in thousands of red giants by
the space missions CoRoT and Kepler, allow us to greatly improve our
understanding of stellar structure and evolution in cool low-mass stars. The currently
available Kepler light curves contain an outstanding amount of
information, but a detailed analysis of the individual oscillation modes in the observed
power spectra, also known as peak bagging, is computationally demanding and challenging to
perform on a large number of targets.Aims. Our intent is to perform for the first time a peak bagging
analysis on a sample of 19 low-mass low-luminosity red giants observed by
Kepler for more than four years. This allows us to provide high-quality
asteroseismic measurements that can be exploited for an intensive testing of the physics
used in stellar structure models, stellar evolution, and pulsation codes, as well as for
refining existing asteroseismic scaling relations in the red giant branch regime.Methods. For this purpose, powerful and sophisticated analysis tools are
needed. We exploit the Bayesian code Diamonds, using an efficient nested sampling
Monte Carlo algorithm, to perform both a fast fitting of the individual oscillation modes
and a peak detection test based on the Bayesian evidence.Results. We find good agreement for the parameters estimated in the
background fitting phase with those given in the literature. We extract and characterize a
total of 1618 oscillation modes, providing the largest set of detailed asteroseismic mode
measurements ever published. We report on the evidence of a change in regime observed in
the relation between linewidths and effective temperatures of the stars occurring at the
bottom of the red giant branch. We show the presence of a linewidth depression or plateau
around νmax for all the red giants of the sample.
Lastly, we show a good agreement between our measurements of maximum mode amplitudes and
existing maximum amplitudes from global analyses provided in the literature, proving that
amplitude scaling relations can be used as empirical tools to improve and simplify the
future peak bagging analysis on a larger sample of evolved stars.
Origine : Publication financée par une institution
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