The Gaia-ASAS-SN classical Cepheids sample: I. Sample Selection

TL;DR

This paper compiles a comprehensive all-sky sample of Milky Way classical Cepheids by combining Gaia DR2 and ASAS-SN data, providing a well-characterized, nearly complete catalog for population studies and follow-up observations.

Contribution

It introduces the largest, well-defined all-sky sample of Galactic Cepheids with a clear selection function, combining Gaia and ASAS-SN data for improved classification and completeness.

Findings

Approximately 1900 likely Galactic Cepheids identified

Sample is >90% complete and pure within criteria

About 130 Cepheids are newly documented in literature

Abstract

We present a well-defined and characterized all-sky sample of classical Cepheids in the Milky Way, obtained by combining two time-domain all-sky surveys: Gaia DR2 (Gaia Collaboration et al. 2018) and ASAS-SN (Shappee et al. 2014). We first use parallax and variability information from Gaia to select ~30,000 bright (G<17) Cepheid candidates with M_K<-1. We then analyze their ASAS-SN V-band lightcurves, determining periods, and classifying the lightcurves using their Fourier parameters. This results in ~1900 likely Galactic Cepheids, which we estimate to be >90% complete and pure within our adopted selection criteria. This is the largest all-sky sample of Milky Way Cepheids that has such a well-characterized selection function, needed for population modeling and for systematic spectroscopic follow-up foreseen with SDSS-V. About 130 of these Cepheids have not been documented in the literature even as possible candidates.