American Astronomical Society, Research Notes of the American Astronomical Society, 5(8), p. 131, 2024
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Abstract Gamma Trianguli Australis is a nearby A-type star that was reported to be a 488 days astrometric binary in Gaia DR3. Here we report on a VLTI/GRAVITY observation of γ TrA in which we did not detect the companion down to a K band flux ratio of 0.5%. From the isochrone mass M A = 3.04M ⊙ of the subgiant primary, this implies a semimajor axis a orb = 1.8 au and that the companion is a M B = 0.26M ⊙ M dwarf. The primary disk is partially resolved with an angular diameter θ 1 ≈ 1 mas ↔ 13.0R ⊙. The differential visibility phases across the Brγ absorption line allowed us to measure the longitude of the ascending node of the primary’s rotational plane Ωrot = 212° ± 3°. This implies a spin–orbit misalignment of at least 27° ± 3° based on the Gaia astrometric solution.