研究成果藝廊

FS Tau B is one of the few T Tauri stars that possess a jet and a counterjet as well as an optically visible cavity wall. We obtained images and spectra of its jet-cavity system in the near-infrared H and K bands using the Subaru/Infrared Camera and Spectrograph and detected the jet and the counterjet in the [Fe II] 1.644 µm line for the first time. Within 2” the blueshifted jet is brighter, whereas beyond ∼ 5” the redshifted counterjet dominates the [Fe II] emission. The innermost blueshifted knot is spectrally resolved to have a large line width of ∼ 110 km/s, while the innermost redshifted knot appears spectrally unresolved. The velocity ratio of the jet to the counterjet is ∼ 1.34, which suggests that FS Tau B is driving an asymmetric jet, similar to those found in several T Tauri stars (e.g., HL Tau, RW Aur A, HH 30). Combining with optical observations in the literature, we showed that the blueshifted jet has a lower density and higher excitation than the redshifted counterjet. We suggest that the asymmetry in brightness and velocity is the manifestation of a bipolar outflow driving at different mass-loss rates, while maintaining balance of linear momentum. A full explanation of the asymmetry in the FS Tau B system awaits detail modeling and further investigation of the kinematic structure of the wind-associated cavity walls. (Liu et al. 2012, ApJ, 749, 62)