Lunch Talk: Don Dixon (Vanderbilt University)

Evolved stars typically rotate very slowly due to magnetic braking during their main-sequence lifetime and/or envelope expansion as they begin to ascend the Red Giant Branch. Despite these spin-down mechanisms some giants are observed to be rapidly rotating (vsini > 10 km/s) and that rotation has been found to strongly correlate with excess emission in the ultraviolet, which can serve as a proxy for magnetic activity. In a previous publication we characterized excess emission in the GALEX NUV bandpass as a function of APOGEE vsini and found similarities to rotationally driven activity in M dwarf stars. Using APOGEE DR17 we expand from the 133 systems in the aforementioned work to 6715 systems to investigate the effects of metallicity and binarity. In this pursuit we derive a second order empirical relation for expected NUV excess given metallicity and vsini. Additionally, we use the maximum difference of sampled RV measurements (RVDmax) to identify systems with close binary companions and find fast rotating giants are more significantly more common in binaries and that the binaries tend to have a larger NUV excess at similar levels of rotation. We also showcase parameter distributions of systems in special categories including sub-subgiants, anomalously cool stars, near breakup stars and near roche-limit stars. Lastly, we discuss potential future applications using TESS light curve data in regards to further characterizing these systems from spot modulation, ellipsoidal variations and eclipsing binaries.