Gaia Data Release 2

All-sky classification of high-amplitude pulsating stars

¹ Department of Astronomy, University of Geneva, Chemin d’Ecogia 16, 1290 Versoix, Switzerland
e-mail: Lorenzo.Rimoldini@unige.ch
² Department of Astronomy, University of Geneva, Chemin des Maillettes 51, 1290 Versoix, Switzerland
³ SixSq, Rue du Bois-du-Lan 8, 1217 Meyrin, Switzerland
⁴ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁵ AURA/LSST, 950 N Cherry Avenue, Tucson, Arizona 85719, USA
⁶ GÉPI, Observatoire de Paris, Université Paris Sciences & Lettres, CNRS, Place Jules Janssen 5, 92195 Meudon, France
⁷ Institute of Global Health, 9 Chemin des Mines, 1202 Geneva, Switzerland
⁸ Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁹ Departamento Inteligencia Artificial, Universidad Nacional de Educación a Distancia, Calle Juan del Rosal 16, 28040 Madrid, Spain
¹⁰ Departamento de Astrofísica, Centro de Astrobiología (INTA-CSIC), PO Box 78, 28691 Villanueva de la Cañada, Spain
¹¹ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Via Gobetti 93/3, 40129 Bologna, Italy
¹² INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
¹³ Konkoly Observatory, Research Centre for Astronomy & Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklós út 15–17, 1121 Budapest, Hungary
¹⁴ MTA CSFK Lendület Near-Field Cosmology Research Group, Konkoly Thege Miklós út 15–17, 1121 Budapest, Hungary
¹⁵ Department of Astronomy, Eötvös Loránd University, Pázmány Péter sétány 1/a, 1117 Budapest, Hungary
¹⁶ Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, 1180 Vienna, Austria
¹⁷ Telespazio Vega UK Ltd for ESA/ESAC, Camino bajo del Castillo, s/n, Urbanizacion Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain

Received: 9 November 2018
Accepted: 17 March 2019

Abstract

Context. More than half a million of the 1.69 billion sources in Gaia Data Release 2 (DR2) are published with photometric time series that exhibit light variations during the 22 months of observation.

Aims. An all-sky classification of common high-amplitude pulsators (Cepheids, long-period variables, δ Scuti/SX Phoenicis, and RR Lyrae stars) is provided for stars with brightness variations greater than 0.1 mag in G band.

Methods. A semi-supervised classification approach was employed, firstly training multi-stage random forest classifiers with sources of known types in the literature, followed by a preliminary classification of the Gaia data and a second training phase that included a selection of the first classification results to improve the representation of some classes, before the improved classifiers were applied to the Gaia data. Dedicated validation classifiers were used to reduce the level of contamination in the published results. A relevant fraction of objects were not yet sufficiently sampled for reliable Fourier series decomposition, consequently classifiers were based on features derived from statistics of photometric time series in the G, G_BP, and G_RP bands, as well as from some astrometric parameters.

Results. The published classification results include 195 780 RR Lyrae stars, 150 757 long-period variables, 8550 Cepheids, and 8882 δ Scuti/SX Phoenicis stars. All of these results represent candidates whose completeness and contamination are described as a function of variability type and classification reliability. Results are expressed in terms of class labels and classification scores, which are available in the vari_classifier_result table of the Gaia archive.