Letter to the Editor

T CrA has a companion

First direct detection of T CrA B with VLTI/MATISSE^⋆

¹ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, HUN-REN, Konkoly-Thege Miklós út 15-17, 1121 Budapest, Hungary
² CSFK, MTA Centre of Excellence, Konkoly-Thege Miklós út 15-17, H-1121 Budapest, Hungary
³ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Nice, France
⁴ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁵ Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany
⁶ ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
⁷ Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstr. 15, 24118 Kiel, Germany
⁸ Leiden Observatory, Leiden University, PO Box 9513 2300 RA Leiden, The Netherlands
⁹ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, The Netherlands
¹⁰ Institute for Astronomy (IfA), University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna, Austria
¹¹ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹² Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, UT3-PS, CNRS, CNES, 9 av. du Colonel Roche, 31028 Toulouse Cedex 4, France
¹³ NASA Goddard Space Flight Center, Astrophysics Division, Greenbelt, MD, 20771, USA

^⋆⋆ Corresponding author; varga.jozsef@csfk.org

Received: 13 December 2024
Accepted: 4 March 2025

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).