Yunnan Observatories of the Chinese Academy of Sciences and Aarhus University researchers have found a constraint of the convective core overshoot in low-mass stars and a correlation between the strength of overshoot and the stellar mass. The study was published in Monthly Notices of the Royal Astronomical Society.
The convective overshoot mixing refreshes fuel in the stellar core and then prolongs the lifetime of stars. It is the largest uncertainty in the current theory of the stellar evolution. It is important for the stellar structure and evolution and the age determination of star clusters.
The 3He fusion is efficient enough to drive a convective core in solar-mass stars near the zero-age main sequence, for the solar-mass stars. The convective core should vanish in the 3He burning timescale of about 1–10 Myr, if the overshoot is not taken into account. The core overshoot mixing refuels 3He in the core and significantly prolongs the lifetime of the convective core. It effects the structure of the core of stars.
The observations sensitive to the core and helioseismic/asteroseismic data and the neutrino fluxes caused by nuclear fusion. It can be used to probe the convective overshoot mixing in stellar interior.
Scientists modeled the sun and some Kepler solar-like stars with varied strength of the convective core overshoot mixing. They compared the helioseismic/asteroseismic properties and the solar neutrino fluxed of the stellar models with the observations. The helioseismic inferences of sound speed and density profiles and the observations of the solar neutrino fluxes strongly excluded a convective core at the present solar age, for the sun. It resulted a reliable upper limit of the strength of the convective core overshoot.