A search for T Tauri's optical companion star

Abstract

Speckle interferometric observations of the pre-main-sequence stellar system T Tauri at 650 and 800 nm, and at 1.6 (H) and 2.2 µm (K) in the infrared using the Palomar 200 in. telescope yield no evidence for a tertiary optical companion star as reported in 1985. The present observations were of sufficient sensitivity to have detected the object unambiguously if it had remained at its reported brightness and color. The infrared results provide particularly stringent limits on the presence of a third star in the system, since both the optical and southern infrared component are clearly resolved to the diffraction limit of the 200 in. telescope, including the H band where the southern component appeared ~5 mag fainter than the optical primary. We discuss possible resolutions to the conflicting results concerning this object, and conclude that if the star is bound to the T Tau system, it has dimmed by at least 1-3 mag at R, I, H, and K. In addition, we note that the star is unlikely to be a normal M dwarf as reported, and we discuss the possibility that the star could be a Herbig-Haro object.