Gaia Data Release 1 - The Cepheid & RR Lyrae star pipeline and its application to the south ecliptic pole region

TL;DR

This paper describes the Gaia Data Release 1 pipeline for identifying and characterizing Cepheids and RR Lyrae stars in the south ecliptic pole region, including new discoveries and detailed analysis of variable stars.

Contribution

Development of the SOS pipeline tailored for Gaia's G-band data, enabling the first comprehensive catalog of Cepheids and RR Lyrae stars in the SEP region with new discoveries.

Findings

Catalog of 3,194 variable stars including 599 Cepheids and 2,595 RR Lyrae stars.

Identification of 386 new variable stars by Gaia.

Distribution of stars extends over a 38-degree region near the LMC.

Abstract

We present an overview of the Specific Objects Study (SOS) pipeline developed within the Coordination Unit 7 (CU7) of the Gaia Data Processing and Analysis Consortium (DPAC), the coordination unit charged with the processing and analysis of variable sources observed by Gaia, to validate and fully characterise Cepheids and RR Lyrae stars observed by the spacecraft. We describe how the SOS for Cepheids and RR Lyrae stars (SOS Cep&RRL) was specifically tailored to analyse Gaia's G-band photometric time-series with a South Ecliptic Pole (SEP) footprint, which covers an external region of the Large Magellanic Cloud (LMC). G-band time-series photometry and characterization by the SOS Cep&RRL pipeline (mean magnitude and pulsation characteristics) are published in Gaia Data Release 1 (Gaia DR1) for a total sample of 3,194 variable stars, 599 Cepheids and 2,595 RR Lyrae stars, of which 386 (43 Cepheids and 343 RR Lyrae stars) are new discoveries by Gaia. All 3,194 stars are distributed over an area extending 38 degrees on either side from a point offset from the centre of the LMC by about 3 degrees to the north and 4 degrees to the east. The vast majority, but not all, are located within the LMC. The published sample also includes a few bright RR Lyrae stars that trace the outer halo of the Milky Way in front of the LMC.