Eclipsing binaries occur only in the red-excess class of 9,786 Gaia DR3 astrometric white-dwarf-candidate binaries; TESS shows no signal at predicted outer conjunctions

We tested 9,786 Gaia DR3 astrometric binaries from Shahaf et al. (2024). Their faint companions are not single main-sequence stars. 3,166 systems have no red colour excess (NCE, probable white dwarfs). 6,620 have a red excess (RCE, probable triples). First, we propagated the full Gaia orbit covariance to the conjunction times in the TESS era. We searched 970 TESS full-frame-image light curves of the 261 most edge-on systems, with pooled false-alarm controls and injection-recovery. We expected 23.4 aligned conjunctions on usable data. No vetted signal occurs at a predicted conjunction. Six windows pass the 0.003 threshold, against 4.2 expected false alarms. Vetting shows systematics or eclipses of an inner binary. This test has almost no power for white-dwarf self-lensing (0.22 expected detections), because the pulses are short and small for stars of G about 14. But 9.7 detections of 5 % eclipses were expected if each companion were one opaque star-sized body. Second, eclipsing binaries occur only in the RCE class. The Gaia DR3 eclipsing-binary table contains 21 of 6,620 RCE and 0 of 3,166 NCE systems (Fisher p = 2.7e-4; p = 6e-4 stratified in magnitude and parallax). Our TESS periodic search finds eclipses on target in 12 of 189 RCE and 0 of 72 NCE systems (p = 0.019); 11 of these 12 are not in the Gaia DR3 table. Third, the outer orbits of the Gaia eclipsing systems are closer to edge-on than other RCE orbits (mean |cos i| 0.295 against 0.519; p = 1.6e-4). This agrees with partial alignment of the inner and outer orbits (mutual-inclination scale about 15 to 30 degrees in a simple model). These results support the triage: close eclipsing binaries occur among RCE systems, not among probable white-dwarf systems. Limitations: no spectra; in 8 of 21 Gaia systems the eclipsing pair probably dominates the light; catalogue cross-matches with VSX failed; the conjunction test does not limit the white-dwarf fraction. We report no new planet or self-lensing binary.

Gaia DR3 · astrometric binaries · white dwarfs · self-lensing · TESS · eclipsing binaries · hierarchical triples · mutual inclination · non-single stars · null result