The updated H-band spectral line list (from \lambda 15,000 - 17,000\AA) adopted by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) for the SDSS IV Data Release 16 (DR16) is presented here. The APOGEE line list is a combination of atomic and molecular lines with data from laboratory, theoretical, and astrophysical sources. Oscillator strengths and damping constants are adjusted using high signal-to-noise, high-resolution spectra of the Sun and alpha Boo (Arcturus) as "standard stars". Updates to the DR16 line list, when compared to the previous DR14 version, are the inclusion of molecular H_2O and FeH lines, as well as a much larger (by a factor of ~4) atomic line list, which includes significantly more transitions with hyperfine splitting. More recent references and line lists for the crucial molecules CO and OH were used, as well as for C_2 and SiH. In contrast to DR14, DR16 contains measurable lines from the heavy neutron-capture elements cerium (as Ce II), neodymium (as Nd II), and ytterbium (as Yb II), as well as one line from rubidium (as Rb I), that may be detectable in a small fraction of APOGEE red giants.
@article{arxiv.2103.10112,
title = {The APOGEE Data Release 16 Spectral Line List},
author = {Verne V. Smith and Dmitry Bizyaev and Katia Cunha and Matthew D. Shetrone and Diogo Souto and Carlos Allende Prieto and Thomas Masseron and Szabolcs Meszaros and Henrik Jonsson and Sten Hasselquist and Yeisson Osorio and D. A. Garcia-Hernandez and Bertrand Plez and Rachael L. Beaton and Jon Holtzman and Steven R. Majewski and Guy S. Stringfellow and Jennifer Sobeck},
journal= {arXiv preprint arXiv:2103.10112},
year = {2021}
}