Stellar evolution dredge up1/3/2024 ![]() ![]() ![]() In stars with increasing mass, the convective envelope during the RGB dredges up increasing amounts of CNO-processed material from regions where H was partly but not completely burned to helium on the MS. The trends of birth C and NĪbundances with and could affect spectroscopic ageĮstimates for red giants that rely on the observed C/N ratio as a diagnosticīecause the reaction 14N(p, γ) 15O is much slower than other reactions in the CNO cycle, the abundance of 14N is drastically increased in regions of CNO burning, primarily at the expense of 12C. (“thick disc”) stars and low- (“thin disc”) stars. Substantial separation in birth ratios between high. Trends in the MaNGA integral field survey of nearby galaxies. The stellar N/O trend agrees well with DopitaĮt al.’s calibration of gas phase log(N/O) with metallicity, and with gas phase ![]() Applying mixing corrections to theĪPOGEE abundances removes the observed age-dependence of log(N/O) and log(C/N),īut it leaves trends of log(N/O) and log(C/N) with metallicity, as expectedīased on nucleosynthesis models. “extra” mixing processes fail, predicting trends with surface gravity orĮvolutionary state that are not observed. To within plausible uncertainties in the birth abundances. Our models with standard mixing can reproduce the observed trends Mixing, then apply these models to derive birth C, N, and O abundances for ![]() Masses from Kepler, we test theoretical stellar models that predict this ∼ 5100 stars with elemental abundances from APOGEE and asteroseismic Material mixed into the stars’ convective envelopes. The third dredge-up phenomenon in asymptotic giant branch (AGB) stars is analyzed through evolutionary model calculations of a \mass.Surface abundances of C, N, and O in red giants are affected by processed ![]()
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