HeI{lambda}10830 in red giant stars with HET/HPF

This transition is an indicator of chromospheric activity and/or mass loss in red giants. The majority of stars in our sample reside in the red clump or red horizontal branch based on their V-J, M_V_ color-magnitude diagram, and Gaia Teff and log(g) values.

Most of our target stars are Li-poor in the sense of having normally low Li abundances, defined here as log {epsilon}(Li)<1.25. Over 90% of these Li-poor stars have weak {lambda}10830 features. However, more than half of the 83 Li-rich stars (log{epsilon}(Li)>1.25) have strong {lambda}10830 absorptions.