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

TL;DR

This paper reports the discovery of a binary central star in planetary nebula PN G283.7-05.1, likely originating from a post-red-giant-branch event, with detailed modelling revealing its properties and challenging existing evolutionary models.

Contribution

It provides the first detailed characterisation of a post-RGB planetary nebula central star with a binary system, highlighting its unique evolutionary status.

Findings

Binary system with a 5.9-hour orbit and a hot pre-white-dwarf

Nebula likely formed from a post-RGB progenitor with low mass (~0.4 M_sun)

Central star's temperature and luminosity challenge post-RGB evolutionary tracks

Abstract

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