A hidden population of massive white dwarfs: two spotted K + WD binaries

March 2024 • 2024MNRAS.529..587R

Authors • Rowan, Dominick M. • Jayasinghe, Tharindu • Tucker, Michael A. • Lam, Casey Y. • Thompson, Todd A. • Kochanek, Christopher S. • Abrams, Natasha S. • Fulton, Benjamin J. • Ilyin, Ilya • Isaacson, Howard • Lu, Jessica R. • Martin, David V. • Nicholson, Belinda

Abstract • The identification and characterization of massive (≳ 0.8 M_⊙) white dwarfs is challenging in part due to their low luminosity. Here, we present two candidate single-lined spectroscopic binaries, Gaia DR3 4014708864481651840 and 5811237403155163520, with K-dwarf primaries and optically dark companions. Both have orbital periods of P ~ 0.45 d and show rotational variability, ellipsoidal modulations, and high-amplitude radial velocity variations. Using light curves from the Transiting Exoplanet Survey Satellite (TESS), radial velocities from ground-based spectrographs, and spectral energy distributions, we characterize these binaries to describe the nature of the unseen companion. We find that both systems are consistent with a massive white dwarf companion. Unlike simple ellipsoidal variables, star-spots cause the light-curve morphology to change between TESS sectors. We attempt to constrain the orbital inclination using PHOEBE binary light-curve models, but degeneracies in the light curves of spotted stars prevent a precise determination. Finally, we search for similar objects using Gaia DR3 and TESS, and comment on these systems in the context of recently claimed compact object binaries.

Links

• PDF https://academic.oup.com/mnras/pdf-lookup/doi/10.1093/mnras/stae517
• ELECTR https://doi.org/10.1093%2Fmnras%2Fstae517
• PREPRINT http://arxiv.org/abs/2307.11146