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Modeling of the stars in the red clump (RC) is challenging, due to theuncertainties associated with the physical processes happening in their coreand during the helium flash. By probing the internal stellar structure,asteroseismology allows us to constrain the core properties of RC stars andeventually improve our understanding of this evolutionary phase. In this work,we aim to quantify the impact on the seismic properties of the RC stars of thetwo main core modeling uncertainties: core boundary mixing, and helium burningnuclear reaction rates. Using the MESA stellar evolution code, we computemodels with different core boundary mixing as well as different $3\alpha$ andcarbon alpha (C-alpha) nuclear reaction rates. We investigate the impact ofthose parameters on the period spacing $\Delta \Pi$, which is a probe of theregion around the core. We find that different core boundary mixing schemesyield significantly different period spacings, with differences of 30s betweenthe maximal $\Delta \Pi$ value computed with semiconvection and maximalovershoot. We show that increasing the rate of the C-alpha reaction lengthensthe core helium burning phase, which extends the range of $\Delta \Pi$ coveredby the models during their evolution. This results in a difference of 10sbetween the models computed with a nominal rate and a rate multiplied by 2,which is larger than the observational uncertainties. The effect of changingthe 3$\alpha$ reaction rate is comparatively small. In conclusion, the coreboundary mixing is the main source of uncertainty regarding the seismicmodeling of RC stars. Moreover, the effect of the C-alpha reaction rate isnon-negligible, even if difficult to disentangle from the effect of the mixing.Such degeneracy could be raised in the future, thanks to new seismic data fromthe PLATO mission and theoretical constraints from numerical simulations.

Effect of nuclear reactions rates and core boundary mixing on the seismology of red clump stars