Abstract
We have used the Habitable Zone Planet Finder (HPF) to gather high resolution, high signal-to-noise near-infrared spectra of 13 field red horizontal-branch (RHB) stars, one open-cluster giant, and one very metal-poor halo red giant. The HPF spectra cover the 0.81−1.28 μm wavelength range of the yzJ bands, filling in the gap between the optical (0.4−1.0 μm) and infrared (1.5−2.4 μm) spectra already available for the program stars. We derive abundances of 17 species. Light element transitions dominate the HPF spectra of these red giants, and HPF data can be used to derive abundances from species with poor or no representation in optical spectra (e.g., C I, P I, S I, K I). Attention is drawn to the HPF abundances in two field solar-metallicity RHB stars of special interest: one with an extremely low carbon isotopic ratio, and one with a rare very large lithium content. The latter star is unique in our sample by exhibiting very strong He i 10830 ̊A absorption. Detections of C I and S I in HD 122563 are reported, yielding the lowest metallicity determination of [S/Fe] from multiple transitions.
