The White Dwarf Binary Pathways Survey -- IX. Three long period white dwarf plus subgiant binaries

Abstract

Virtually all binaries consisting of a white dwarf with a non-degenerate companion can be classified as either close post-interaction systems (with orbital periods of a few days or less), or wide systems (with periods longer than decades), in which both components have effectively evolved as single stars. Binaries with periods between these two extremes can help constrain common envelope efficiency, or highlight alternative pathways towards the creation of compact binaries. To date such binaries have remained mostly elusive. Here we present three white dwarfs in binaries with evolved subgiant stars with orbital periods of 41, 52 and 461 d. Using Hubble Space Telescope spectroscopy we find that all three systems contain low mass white dwarfs ($\le$0.4 M${}_{\odot }$). One system, TYC 8394$-$1331$-$1, is the inner binary of a hierarchical triple, where the white dwarf plus subgiant binary is orbited by a more distant companion star. These binaries were likely formed from a phase of stable but non-conservative mass transfer, as opposed to common envelope evolution. All three systems will undergo a common envelope phase in the future, but the two shorter period systems are expected to merge during this event, while the longest period system is likely to survive and create a close binary with two low mass white dwarfs.

13 pages, 9 figures. Accepted for publication in MNRAS

References in corpus (19)

• Modules for Experiments in Stellar Astrophysics (MESA)
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• Tertiary companions to close spectroscopic binaries
• Modern stellar spectroscopy caveats
• Post-common-envelope binaries from SDSS. IX: Constraining the common-envelope efficiency
• Three-dimensional mapping of the local interstellar medium with composite data
• CERES: A Set of Automated Routines for Echelle Spectra
• The Gaia FGK Benchmark Stars - High resolution spectral library
• Monte Carlo simulations of post-common-envelope white dwarf + main sequence binaries: comparison with the SDSS DR7 observed sample
• Adiabatic mass loss in binary stars. III. From the base of the red giant branch to the tip of asymptotic giant branch
• KOI-3278: A Self-Lensing Binary Star System
• Monte Carlo simulations of post-common-envelope white dwarf + main sequence binaries: The effects of including recombination energy
• Close detached white dwarf + brown dwarf binaries: further evidence for low values of the common envelope efficiency
• The White Dwarf Binary Pathways Survey IV: Three close white dwarf binaries with G-type secondary stars
• The White Dwarf Binary Pathways Survey VI: two close post common envelope binaries with TESS light curves
• Rotationally Driven Ultraviolet Emission of Red Giant Stars
• The White Dwarf Binary Pathways Survey VII: Evidence for a bi-modal distribution of post mass transfer systems?
• Discovery of a pre-cataclysmic binary with unusual chromaticity of the eclipsed white dwarf by the GPX Survey