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Post Info TOPIC: FS Tauri
Blobrana


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FS Tauri B
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Title: Is FS Tau B Driving an Asymmetric Jet?
Authors: Chun-Fan Liu, Hsien Shang, Tae-Soo Pyo, Michihiro Takami, Frederick M. Walter, Chi-Hung Yan, Shiang-Yu Wang, Nagayoshi Ohashi, Masahiko Hayashi

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 Subaru/IRCS and detected the jet and the counterjet in the [Fe II] 1.644 \mu m line for the first time. Within the inner 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. Combining with optical observations in the literature, we showed that the blueshifted jet has 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 to the asymmetry in the FS Tau B system awaits detail modelling and further investigation of the kinematic structure of the wind-associated cavity walls.

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RE: FS Tauri
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Duo of Big Telescopes Probes the Depths of Binary Star Formation

A team of researchers from four Japanese universities (Kobe, Saitama, Osaka, and Tokyo) has been able to delineate the intricate structure of the circumbinary disk that surrounds a young binary star system from the observation with the Subaru Telescope and the Hubble Space Telescope. By using different wavelengths to examine the system's internal structure, they succeeded in demonstrating a distinct colour difference between its northern and southern portions. The researchers are now prepared to apply their approach of combining optical and near-infrared observations to other regions of binary formation.
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Title: High-Resolution Optical and Near-Infrared Images of the FS Tauri Circumbinary Disk
Authors: Tomonori Hioki, Yoichi Itoh, Yumiko Oasa, Misato Fukagawa, Masahiko Hayashi

We present an H-band image of FS Tauri, a 0.2"-separated classical T Tauri binary system, taken with the Coronagraphic Imager with Adaptive Optics on the Subaru Telescope. This new image, combined with Hubble Space Telescope / Advanced Camera for Surveys F606W-band polarimetric images, shows that the binary has complicated circumbinary features, including a circumbinary disk, western and eastern arm-like structures, and two cavities at the northeast and southwest. The circumbinary disk is 630 AU in radius and the southeast side of the disk is bright in the H-band. The brightness ratio (southeast/northwest) is 1.6. A single Rayleigh-like scattering model indicates that the disk is inclined by 30 degree to 40 degree and that the southeast side corresponds to the near side along our line of sight. The H-band surface brightness of the southeast side decreases as r^(-1.9) from 15.2 mag arcsec^-2 to 16.8 mag arcsec^-2. The outer portion of the disk is possibly more flared than its inner portion. The weak centro-symmetric polarisation pattern and redder F606W-H colour (4.2 mag) of the southeast side are probably caused by multiple scattering events from the dust grains associated with the binary. The F606W-band image shows the bright northwest side of the disk in contrast with the H-band image. The F606W-H color of the northwest side is between 1.7 mag and 3.0 mag. We consider that Haro 6-5 B (FS Tauri B), 20" away, produces the neutral scattered light from the northwest side. This idea is supported by the polarisation pattern of the northwest side, which is centro-symmetric with respect to Haro 6-5 B. The arms appear to encompass the western and eastern cavities, suggesting that the arms + cavity systems are created by a bipolar outflow from the binary. However, the direction of this outflow is inconsistent with that of outflows inferred from the circumbinary disk model.

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