Seismic constraints on the internal structure of evolved stars From high-luminosity RGB to AGB stars. (2021)
Keywords :
asteroseismology - stars evolution - stars: late-type - stars: interiors - stars: AGB and post-AGB - stars: oscillations
Abstract:The space-borne missions CoRoT and Kepler opened up a new opportunity for better understanding stellar evolution by probing stellar interiors with unrivalled high-precision photometric data. Kepler has observed stellar oscillation for four years, which gave access to excellent frequency resolution that enables deciphering the oscillation spectrum of evolved red giant branch and asymptotic giant branch stars. The internal structure of stars in the upper parts of the red and asymptotic giant branches is poorly constrained, which makes the distinction between red and asymptotic giants difficult. We perform a
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Global seismic parameters of the stars listed in the paper. Each star
is identified with its KIC number (Kepler Input Catalog).
The stellar mass and the effective temperature are from the APOKASC
catalogue (Pinsonneault et al., 2014ApJS..215...19P, Cat.
J/ApJS/215/19). For some stars, the stellar mass and the effective
temperature are not listed in the APOKASC catalogue. It concerns
roughly 5% of our sample, with half of this fraction being associated
with very low Dnu-values (i.e. Dnu<=0.5uHz). For these stars, we
nevertheless obtained rough estimates of the stellar mass and
effective temperature using semi-empirical and empirical scaling
relations implying both the frequency at the maximum oscillation power
numax and large frequency separation Dnu (Kjeldsen & Bedding,
1995A&A...293...87K; Kallinger et al., 2010A&A...509A..77K; Mosser et
al., 2010A&A...517A..22M). The stellar classification is performed
following two methods. The first method relies on the envelope
autocorrelation function denoted eta (Mosser et al.,
2019A&A...622A..76M). A star is classified as red giant when
eta>=0.700 and as helium burning star when eta<=0.700. The second
method relies on the acoustic offset (Kallinger et al.,
2012A&A...541A..51K). The evolutionary status is labelled by the
parameter evo with the following code: 0 - RGB star, 1 - red clump
stars, 2 - secondary clump stars, and 3 - AGB stars.
Guillaume Dreau, guillaume.dreau(at)obspm.fr
