A fourth component in the young multiple system V 773 Tau

Abstract

I report on a new component in the pre-main sequence multiple system V 773 Tauri. This second visual companion, V 773 Tau C, with a projected separation of about 0."2 has been detected using speckle interferometry in the near-infrared. Repeated observations from 1996 to 2002 show significant orbital motion and thus confirm the character of the new companion as a gravitationally bound star. Together with the two components of the spectroscopic binary V 773 Tau A and the previously known visual companion V 773 Tau B, the V 773 Tau system appears as a young "mini-cluster" of four T Tauri stars within a sphere of a radius less than 100 AU. V 773 Tau, A, B and C form a triple system that is not hierarchic, but is apparently stable despite of this. The brightness of V 773 Tau C has probably increased over the last years, which may explain its non-detection in previous binary surveys.