The post-common-envelope binary central star of the planetary nebula PN G283.7−05.1^⋆

A possible post-red-giant-branch planetary nebula central star

¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
e-mail: djones@iac.es
² Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
³ European Southern Observatory, Karl-Schwarzschild-str. 2, 85748 Garching, Germany
⁴ Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK
⁵ Isaac Newton Group of Telescopes, Apartado de Correos 368, 38700 Santa Cruz de La Palma, Spain
⁶ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁷ Department of Physics and Astronomy, Valparaiso University, Valparaiso, IN 46383, USA
⁸ Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
⁹ GRANTECAN, Cuesta de San José s/n, 38712 Breña Baja, La Palma, Spain
¹⁰ Astrophysics Research Group, Faculty of Engineering and Physical Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK

Received: 29 June 2020
Accepted: 30 July 2020

Abstract

We present the discovery and characterisation of the post-common-envelope central star system in the planetary nebula PN G283.7−05.1. Deep images taken as part of the POPIPlaN survey indicate that the nebula may possess a bipolar morphology similar to other post-common-envelope planetary nebulae. Simultaneous light and radial velocity curve modelling reveals that the newly discovered binary system comprises a highly irradiated M-type main-sequence star in a 5.9-hour orbit with a hot pre-white dwarf. The nebular progenitor is found to have a particularly low mass of around 0.4 M_⊙, making PN G283.7−05.1 one of only a handful of candidate planetary nebulae that is the product of a common-envelope event while still on the red giant branch. In addition to its low mass, the model temperature, surface gravity, and luminosity are all found to be consistent with the observed stellar and nebular spectra through comparison with model atmospheres and photoionisation modelling. However, the high temperature (T_eff ∼ 95 kK) and high luminosity of the central star of the nebula are not consistent with post-RGB evolutionary tracks.