Towards a more complete sample of binary central stars of planetary nebulae with Gaia

¹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
e-mail: njc89@ast.cam.ac.uk
² Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
³ Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
⁴ ESO, Karl-Schwarzschild-str. 2, 85748 Garching, Germany
⁵ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK

Received: 5 January 2021
Accepted: 11 February 2021

Abstract

Context. Many if not most planetary nebulae (PNe) are now thought to be the outcome of binary evolutionary scenarios. However, only a few percent of the PNe in the Milky Way are known to host binary systems. The high-precision repeated observing and long time baseline of Gaia make it well suited for detecting new close binaries through photometric variability.

Aims. We aim to find new close binary central stars of PNe (CSPNe) using data from the Gaia mission, building towards a statistically significant sample of post-common envelope, close binary CSPNe.

Methods. As the vast majority of Gaia sources do not have published epoch photometry, we used the uncertainty in the mean photometry as a proxy for determining the variability of our CSPN sample in the second Gaia data release. We derived a quantity that expresses the significance of the variability, and considered what is necessary to build a clean sample of genuine variable sources.

Results. Our selection recovers a large fraction of the known close binary CSPN population, while other CSPNe lying in the same region of the parameter space represent a promising set of targets for ground-based confirmatory follow-up observations. Gaia epoch photometry for four of the newly identified variable sources confirms that the variability is genuine and consistent with binarity.