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Title: A hidden population of massive white dwarfs: two spotted K + WD binaries
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.  more » « less
Award ID(s):
2307385 1908570
PAR ID:
10526452
Author(s) / Creator(s):
; ; ; ; ; ; ; ; ; ; ; ;
Publisher / Repository:
Monthly Notices of the Royal Astronomical Society
Date Published:
Journal Name:
Monthly Notices of the Royal Astronomical Society
Volume:
529
Issue:
1
ISSN:
0035-8711
Page Range / eLocation ID:
587 to 603
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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