Program: GS-2021B-Q-320

We propose coordinated multi-epoch IGRINS measurements contemporaneous with TESS monitoring of the Ecliptic plane fields with a goal of spectrally characterizing starspot modulation. The 17 targets are chosen from a parent sample of 516 field sub-giant stars based on a Gaia-DR2-informed HR-diagram. Ten of the targets reside outside of the region consistent with non-magnetic stellar evolution models. These sub-sub-giants (SSGs) are believed to exhibit such a profound coverage of starspots as to inhibit their convective efficiency, altering the trajectory of their evolution. SSGs serve as an excellent testbed to study stellar activity owing to their large amplitude of photometric modulation. We will ultimately derive the starspot coverage fraction and wavelength dependent starspot contrast for these systems, exploring variations with TESS-informed rotational phase. Finally, we will assess whether our IGRINS-measured starspot coverage fractions can produce such conspicuous underluminosities when combined with spotted stellar evolutionary models.