Edge-on disk around the T Tauri star [MR81] Hα17 NE in Corona Australis

Abstract

Aims. Using the speckle camera SHARP at the 3.5 m ESO NTT, Kohler and collaborators found an object ∼3.5 mag fainter in K only 1.3 �� north-east of the T Tauri star [MR81] Hα17 in the Corona Australis (CrA) star-forming region, which could be either a brown dwarf or a T Tauri star with an edge-on disk. We attempt to study this faint object in detail. Methods. We acquired deep VLT NACO near-infrared images at three epochs to determine, whether [MR81] Hα17 and the nearby faint object are comoving and to measure the infrared colors of both objects. We obtained optical and infrared spectra of both objects with the VLT using FORS and ISAAC, respectively, to determine spectral types and temperatures as well as ages and masses. Results. The T Tauri star [MR81] Hα17 and the faint nearby object have a projected separation of 1369.58 mas, i.e. 178 AU at 130 pc. They share the same proper motion (∼5σ), so that they most certainly form a bound binary pair. The apparently fainter component [MR81] Hα17 NE has a spectral type of M2e, while the apparently brighter component [MR81] Hα17 SW, the previously known T Tauri star, has a spectral type of M4-5e. We can identify a nearly edge-on disk around [MR81] Hα17 NE by visual inspection, which has a diameter of at least 30 to 50 AU. We are able to detect strong emission lines in [MR81] Hα17 NE, which are almost certainly due to ongoing accretion. The NE object is detectable only by means of its scattered light. Conclusions. If both objects are co-eval (2–3 Myr) and located at the same distance (∼130 pc as CrA), then the apparently fainter [MR81] Hα17 NE is more massive (primary) component with a nearly edge-on disk and the apparently brigther component [MR81] Hα17 SW is less massive (companion). Both are low-mass T Tauri stars with masses of ∼0.5 and 0.23 ± 0.05 M� , respectively.