TESS shows transits for only 8 of about 1,258 expected Gaia DR3 SB1 brown-dwarf candidates (4,164 stars, P < 40 d), and for none below 3 days

Question: are the Gaia DR3 single-lined spectroscopic (SB1) orbits with brown-dwarf minimum masses real? An edge-on real companion must transit at the Gaia period and conjunction time. Approach: we took all 4,254 Gaia DR3 SB1 orbits with P < 40 d and m2 sin i = 13-80 MJ, plus planet-mass, 80-150 MJ and stellar-companion control samples (7,836 stars). We folded MIT QLP TESS light curves of sectors 1-105 at the Gaia period (+-3 sigma) near the predicted conjunction, with control periods, injected 1 RJ transits (mean completeness 0.95) and visual vetting. Results: for 297 eclipsing stellar-companion binaries the TESS eclipse time agrees with the Gaia prediction (84% within 2 sigma, robust width 1.10 sigma), and stellar-companion orbits give 0.98-1.08 of the expected eclipses for P > 1 d. For 4,164 brown-dwarf candidates with data we expect 1,258 transits and find 8 transit-like, BD-compatible signals: 0.64% (95% interval 0.27-1.25%; 0.4-0.9% across variants). There are no transits for P < 3 d (1,092 expected) and none for m2 sin i < 40 MJ (450 expected); for P = 3-10 d the fraction is 5% (2-10%). Twenty-nine short-period (0.4-1.3 d) candidates show ellipsoidal or contact-binary light curves and four show stellar eclipses, so their Gaia RV amplitudes are too small. We recover TOI-503 b, TOI-148 b, TOI-2533 b and WASP-18 b, and find one new transit-like signal at the Gaia conjunction: TIC 127799366 (P = 5.4937 d, m2 sin i 64 MJ, R2 about 1 RJ). The result repeats and extends an earlier campaign study that used TESS-SPOC data (P < 10 d); of its 47 candidates in our sample, 11 repeat as eclipse-like, 10 are sinusoidal and 26 are not detected. Limitations: single-analyst visual classes; QLP detrending changes depths; no dilution correction; the test cannot separate spurious orbits from inclined stellar companions; no follow-up of the new candidate.

Gaia DR3 · spectroscopic binaries · SB1 orbits · brown dwarfs · brown-dwarf desert · TESS · QLP · transits · eclipsing binaries · ephemeris validation · ellipsoidal variables · false positives · TIC 127799366