Detection of shocked molecular hydrogen in infrared companions to T Tauri stars: Evidence for ongoing accretion

Abstract

We report the detection of the 2.12 micrometers, nu = 1-0 S(1) emission line of molecular hydrogen spatially confined to the infrared companions of the Haro 6-10 and UY Aur binary systems. The primaries in both sources appear to be relatively normal pre-main-sequence stars. The K-band spectrum of the Haro 6-10 companion is unusually red and displays no characteristic stellar features. The UY Aur infrared companion, on the other hand, is undoubtedly a star. Our nondetection of the nu = 2-1 S(1) line of H2 implies line ratios inconsistent with a fluorescent origin for the emission and suggests that it is produced by shock heating. These observations strengthen the view that the infrared companions are experiencing ongoing accretion.