• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.249-252
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• 2005

We present results of the velocity-resolved spectroscopy of the [Fe II] $\lambda$1.644${\mu}m$ emission toward outflow sources with the Subaru Telescope at the angular resolution of 0.apos;16 ${\~}$ 0.apos;5 arcseconds. The observed sources are L1551 IRS 5, DG Tau, HL Tau and RW Aur, which are located in the Taurus-Aurigae Molecular Cloud, one of the closest star forming regions (0.apos;1 = 14 AU). We were able to resolve outflow structure in the vicinity of the sources at a scale of a few tens of AU. The position-velocity diagram of each object shows two velocity components: the high velocity component (HVC: 200 - 400 km $s^{-l}$) and the low velocity component (LVC: 50 - 150 km $s^{-l}$), which are clearly distinct in space and velocity. The HVC may be a highly collimated jet presumed from its narrow velocity width and high velocity. The LVC, on the other hand, may be a widely opened disk wind inferred from its broad velocity width and low velocity. The spectrum taken perpendicular to the L1551 IRS 5 outflow at its base shows that the LVC has a spatially wide subcomponent, supporting the above interpretation. We demonstrated that the [Fe II] 1.644 $\mu$ spectroscopy is a very powerful tool for the studies of fast jets and winds that directly emanate from star-disk systems.

• Journal of The Korean Astronomical Society
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• v.29 no.spc1
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• pp.263-264
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• 1996

We have solved the radiative transfer problem using a Sobolev approximation with an escape probability method in case of the supersonic expansion of a stellar envelope to an ambient medium. The radiation from the expanding envelope turns out to produce a P-Cygni type profile. In order to investigate the morphology of the theoretical P-Cygni type profile, we have treated $V{\infty},\;V_{sto},\;{\beta}$ (parameter for the velocity field), M and $\epsilon$ (parameter for collisional effect) as model parametrs. We have found that the velocity field and the mass loss rate affect the shapes of the P-Cygni type profiles most effectively. The secondarily important factors are $V{\infty},\;V_{sto}$. The collisional effect tends to make the total flux increase but not so .much in magnitude. We have infered some physical parameters of 68 Cyg, HD24912, and $\xi$ persei such as V$\infty$, M from the model calculation, which shows a good agreement with the observational results.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.140.2-140.2
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• 2012

The silicate carbon star IRAS 09425-6040 shows very conspicuous crystalline silicate dust features and excessive emission at far infrared. To investigate properties of dusty envelopes around the object, we use radiative transfer models for axisymmetric and sphericallly symmetric dust distributions. We perform model calculations for various possible combinations of dust shells and disks with various dust species. We compare the model results with the observed spectral energy distributions (SEDs) including the IRAS, ISO, AKARI, MSX and 2MASS data. We find that a model with multiple disks of amorphous and crystalline silicate and multiple spherical shells of carbon dust can reproduce the observed SED fairly well. This supports the scenario for the origin of silicate carbon stars that oxygen-rich material was shed by mass loss when the primary star was an M giant and the O-rich material is stored in a circumbinary disk. Highly (about 75 %) crystallized forsterite dust in the disk can reproduce the conspicuous crystalline features of the ISO observational data. This object looks to have a detached silicate and H2O ice shell with a much higher mass-loss rate. It could be a remnant of the chemical transition phase. The last phase of stellar winds of O-rich materials looks to be a superwind.