Self-lensing Signals in Binary Systems Containing White Dwarfs with Neutron Star or Stellar-mass Black Hole Companions

Light curves from binary systems containing white dwarfs (WDs) with neutron star (NS) or stellar-mass black hole (BH) companions with edge-on orbital planes potentially show self-lensing/eclipsing signals. Here, we evaluate the properties and detectability of these signals in NASA’s Transiting Exoplanet Survey Satellite (TESS) and the Nancy Grace Roman Space Telescope (Roman) observations. WD+NS systems with orbital periods T ≲ 25 days mostly have considerable finite-source sizes with the normalized source radii ρ ⋆ ≳ 1. WD+BH systems with T ≳ 3 days have ρ ⋆ ≲ 1, and ρ ⋆ ∼ 0.01 for BHs with a few tens of solar masses. Our analytical calculations show the probabilities of occurring self-lensing signals in WD+NS and WD+BH systems are ∼10 −3 , 10 −2 , and maximize for systems with low-mass WDs revolving massive NSs/BHs. We simulate their light curves and generate synthetic data for them by applying the observing protocols of these two satellites. We assume self-lensing signals are detectable if (i) 1 ≤ T ≤ T obs (where T obs = 62 and 27.4 days are the Roman and TESS continuous observing windows), (ii) have signal-to-noise ratios ≥ 3, 6, and their signals are (iii) deeper than twice the photometric error and (iv) covered by at least one datum. Systems with detectable self-lensing signals in the TESS and Roman observations on average have small inclination angles i ≲ 0 . ° 2, with the orbital periods ∼6, 19 days, and their signals last ∼[6, 30] minutes. The TESS and Roman efficiencies for detecting these signals are ∼2−6 × 10 −4 and ∼2−12 × 10 −10 . Although detecting these self-lensing signals by Roman is impossible, the TESS telescope potentially manifests at least one self-lensing signal due to these binary systems, if 8% and 3% of WDs have NS and BH companions, respectively.