T CrA has a companion

Abstract

T CrA is a Herbig Ae-type young star in a complex circumstellar environment; it includes a circumstellar disk, accretion streamers, jets, and outflows. It has long been suspected to be a binary. However, until now, there has been no direct detection of a companion. Here we present new VLTI/MATISSE L- and N-band observations of T CrA taken between 2023 May and 2024 August with the aim of testing the binary nature of the system. We modeled the data with a geometric model using the Python tool oimodeler. We detected a companion (T CrA B) with a projected separation of Δr = 153.2 ± 1.2 mas (≈23 au) toward the west direction at a position angle of 275.4 ± 0.1°, in 2024 May–August. Our results support that the companion has a nearly edge-on orbit that is highly misaligned with respect to the circumprimary disk. Such a configuration could cause warping and tearing of the disk around the primary, which has been proposed by recent studies. In the L band the companion is extended, with a full width at half maximum (FWHM) size of ∼1 au, suggesting that the emission comes from a disk around the secondary star. The companion flux is 0.2–0.3 Jy in the L band, and 0.2–0.7 Jy in the N band, accounting for 4–20% of the total emission at those wavelengths. The SED of the companion is compatible with thermal radiation of warm dust (600–800 K).