The White Dwarf Binary Pathways Survey IV: Three close white dwarf binaries with G-type secondary stars

TL;DR

This study reports the discovery and analysis of three close white dwarf binaries with G-type secondary stars, expanding understanding of their formation and evolutionary pathways beyond low-mass companions.

Contribution

It presents the first detailed characterization of PCEBs with G-type secondaries and explores their diverse evolutionary outcomes using observational data and modeling tools.

Findings

No differences in common envelope evolution compared to lower-mass secondaries.

Diverse future evolutionary paths for the three systems.

Potential outcomes include cataclysmic variables, mergers, and super soft sources.

Abstract

Constraints from surveys of post common envelope binaries (PCEBs) consisting of a white dwarf plus an M-dwarf companion have led to significant progress in our understanding of the formation of close white dwarf binary stars with low-mass companions. The white dwarf binary pathways project aims at extending these previous surveys to larger secondary masses, i.e. secondary stars of spectral type AFGK. Here we present the discovery and observational characterization of three PCEBs with G-type secondary stars and orbital periods between 1.2 and 2.5 days. Using our own tools as well as MESA we estimate the evolutionary history of the binary stars and predict their future. We find a large range of possible evolutionary histories for all three systems and identify no indications for differences in common envelope evolution compared to PCEBs with lower mass secondary stars. Despite their similarities in orbital period and secondary spectral type, we estimate that the future of the three systems are very different: TYC 4962-1205-1 is a progenitor of a cataclysmic variable system with an evolved donor star, TYC 4700-815-1 will run into dynamically unstable mass transfer that will cause the two stars to merge, and TYC 1380-957-1 may appear as super soft source before becoming a rather typical cataclysmic variable star.