Two unseen massive white dwarf candidates in close binaries

We report the discovery of two binary systems, each consisting of a slightly bloated G-type main-sequence star and an unseen companion, identified through photometric data from TESS and radial velocity variation from Gaia. High-resolution spectroscopy confirms orbital periods of 1.37 and $2.67$ d with circular orbits. The visible components have masses of ~0.9–1.0\, M_, while the minimum masses of the unseen companions are 1.078+0.058-0.060\, M_ and 0.943+0.048-0.049\, M_, respectively. Assuming tidal synchronization, we estimate the companion masses to be 1.13+0.11-0.08\, M_ and 1.05+0.15-0.10\, M_. The absence of detectable spectral features from the companions rules out main-sequence stars of these masses, suggesting that the unseen companions are likely O/Ne or C/O massive white dwarfs. The short orbital periods imply that these systems are post-common envelope binaries. Their subsequent evolution is uncertain, with possible outcomes including cataclysmic variables, Type Ia supernovae, or accretion-induced collapse, depending on the nature of future mass transfer.