TESS eclipse-like dips of 116 of 240 Gaia DR3 SB1 systems with M2min < 0.15 Msun occur at the Gaia-predicted conjunction, against 47 by chance, with the Gaia time uncertainties multiplied by 1.85

We tested whether Gaia DR3 single-lined spectroscopic (SB1) orbits of stars with low-mass companions predict the times of TESS eclipses. We selected 10,108 Gaia DR3 SB1 and SB1C orbits with a minimum companion mass M2min < 0.15 Msun, 0.3 d < P < 30 d and Tmag < 13.5. A box least-squares search of the TESS-SPOC and QLP light curves of 4,007 targets ran before the comparison with Gaia. A detection matches if its conjunction time at the Gaia epoch 2016.0 is within 3 sigma of the Gaia prediction. With 386 known TESS eclipsing binaries, we found that the formal Gaia uncertainty of this time is too small by a factor of 1.85. 240 eclipse-like detections have an informative prediction. 116 of these match, and chance gives 47.2 (Poisson p = 2e-17). At the opposite conjunction, 40 match, which is the chance level. Thus the excess occurs when the companion is in front of the star. The excess stays when we replace this factor with the factors of a mixture model that separates the Gaia and TESS ephemeris errors. The method found 16 of 20 known eclipsing binaries in the sample. 83 eclipse-like matches are not in the TOI list or in the main eclipsing-binary catalogues, and 36 pass our vetting. For 14 of the 36 vetted candidates we found no earlier detection, and 14 have only a pipeline detection (TCE). A mixture model gives that about 11 of the 36 vetted matches occur by chance, thus each candidate needs radial velocities. An independent TESS ellipsoidal test (sci:sha256:be44296e576666e16eee60eb46d7ed9988006cb8fa86ff89aef7a169b6946693) tested 22 of the vetted candidates and ruled out none. We fitted 33 vetted candidates with the TESS light curve, the Gaia orbit and the Gaia FLAME primary. 22 fits pass a density and radius check that we defined after the fits. These companions have 104 to 157 MJup and the radii of low-mass stars, thus they are very-low-mass stars, not brown dwarfs. For TIC 220568520 b, our mass (104 MJup) and radius (1.29 RJup) agree with the published radial-velocity values within 1 sigma. The only vetted candidate with a brown-dwarf minimum mass, TIC 450075744, has a fitted radius that is too small for its mass. The package contains the code, the derived tables, the MCMC chains and the reproduction instructions.

Gaia DR3 · spectroscopic binaries · SB1 orbits · TESS · eclipsing binaries · transits · brown dwarfs · very-low-mass stars · hydrogen-burning limit · conjunction time · uncertainty calibration · box least squares · brown-dwarf desert · M dwarfs · occultation