Variable star classification across the Galactic bulge and disc with the VISTA Variables in the Vía Láctea survey

Abstract

We present VIVACE, the VIrac VAriable Classification Ensemble, a catalogue of variable stars extracted from an automated classification pipeline for the Vista Variables in the Vía Láctea (VVV) infrared survey of the Galactic bar/bulge and southern disc. Our procedure utilizes a two-stage hierarchical classifier to first isolate likely variable sources using simple variability summary statistics and training sets of non-variable sources from the Gaia early third data release, and then classify candidate variables using more detailed light-curve statistics and training labels primarily from OGLE and VSX. The methodology is applied to point-spread-function photometry for ~490 million light curves from the VIRAC v2 astrometric and photometric catalogue resulting in a catalogue of ~1.4 million likely variable stars, of which ~39 000 are high-confidence (classification probability >0.9) RR Lyrae ab stars, ~8000 RR Lyrae c/d stars, ~187, 000 detached/semi-detached eclipsing binaries, ~18, 000 contact eclipsing binaries, ~1400 classical Cepheid variables and ~2200 Type II Cepheid variables. Comparison with OGLE-4 suggests a completeness of around $90\, \, \mathrm{per\, cent}$ for RRab and $\lesssim 60\, \mathrm{per\, cent}$ for RRc/d, and a misclassification rate for known RR Lyrae stars of around $1\, \mathrm{per\, cent}$ for the high confidence sample. We close with two science demonstrations of our new VIVACE catalogue: first, a brief investigation of the spatial and kinematic properties of the RR Lyrae stars within the disc/bulge, demonstrating the spatial elongation of bar-bulge RR Lyrae stars is in the same sense as the more metal-rich red giant population whilst having a slower rotation rate of $\sim \!40\, \mathrm{km\, s}^{-1}\mathrm{kpc}^{-1}$; and secondly, an investigation of the GaiaEDR3 parallax zero-point using contact eclipsing binaries across the Galactic disc plane and bulge.