Red clump stars selected from LAMOST and APOGEE

These stars may have more precise distance estimates from spectrophotometry than from Gaia parallaxes beyond 3kpc. However, RC stars have values of Teff and logg that are very similar to some red giant branch (RGB) stars.

Especially for low-resolution spectroscopic studies where Teff, logg, and [Fe/H] can only be estimated with limited precision, separating RC stars from RGB through established methods can incur ~20% contamination. Recently, Hawkins+ (2018ApJ...853...20H) demonstrated that the additional information in single-epoch spectra, such as the C/N ratio, can be exploited to cleanly differentiate RC and RGB stars. In this second paper of the series, we establish a data-driven mapping from spectral flux space to independently determined asteroseismic parameters, the frequency and the period spacing.