Evidence of structural discontinuities in the inner core of red-giant stars

Red giants are stars in the late stages of stellar evolution. Because they have exhausted the supply of hydrogen in their core, they burn the hydrogen in the surrounding shell . Once the helium in the core starts fusing, the star enters the clump phase, which is identified as a striking feature in t...

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Bibliographic Details
Published in:	Nature communications 2022-12, Vol.13 (1), p.7553-7553
Main Authors:	Vrard, Mathieu, Cunha, Margarida S, Bossini, Diego, Avelino, Pedro P, Corsaro, Enrico, Mosser, Benoît
Format:	Article
Language:	eng
Subjects:	Chemical evolution Color-magnitude diagram Discontinuity Galaxies Helium Hydrogen Red giant stars Stars & galaxies Stellar evolution Stellar seismology Thermal stratification
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Summary:	Red giants are stars in the late stages of stellar evolution. Because they have exhausted the supply of hydrogen in their core, they burn the hydrogen in the surrounding shell . Once the helium in the core starts fusing, the star enters the clump phase, which is identified as a striking feature in the color-magnitude diagram. Since clump stars share similar observational properties, they are heavily used in astrophysical studies, as probes of distance, extinction through the galaxy, galaxy density, and stellar chemical evolution. In this work, we perform the detailed observational characterization of the deepest layers of clump stars using asteroseismic data from Kepler. We find evidence for large core structural discontinuities in about 6.7% of the stars in our sample, implying that the region of mixing beyond the convective core boundary has a radiative thermal stratification. These stars are otherwise similar to the remaining stars in our sample, which may indicate that the building of the discontinuities is an intermittent phenomenon.
ISSN:	2041-1723