Ko Nedachi

DISCOVERY OF EXTREMELY EMBEDDED X-RAY SOURCES IN THE R CORONAE AUSTRALIS STAR-FORMING CORE

With the XMM-Newton and Chandra observatories, we detected two extremely embedded X-ray sources in the R Corona Australis (R CrA) star-forming core, near IRS 7. These sources, designated as XE and XW, have X-ray absorption columns of ~3 × 1023 cm-2 equivalent to AV ~ 180 mag. They are associated with the VLA centimeter radio sources 10E and 10W, respectively; XW is the counterpart of the near-infrared source IRS 7, whereas XE has no K-band counterpart above 19.4 mag. This indicates that XE is younger than typical Class I protostars, probably a Class 0 protostar, or in an intermediate phase between Class 0 and Class I. The X-ray luminosity of XE varied between 29 < log LX < 31.2 ergs s-1 on timescales of 3-30 months; XE also showed a monotonic increase in X-ray brightness by a factor of 2 in 30 ks during an XMM-Newton observation. The XMM-Newton spectra indicate emission from a hot plasma with kT ~ 3-4 keV and also show fluorescent emission from cold iron. Although the X-ray spectrum from XE is similar to flare spectra from Class I protostars in luminosity and temperature, the light curve does not resemble the light curves of magnetically generated X-ray flares, because the variability timescale of XE is too long and variations in X-ray count rate were not accompanied by variations in spectral hardness. The short-term variation of XE may be caused by the partial blocking of the X-ray plasma, while the month-long flux enhancement may be driven by mass accretion.

Diffraction-Limited 3 μm Spectroscopy of IRAS 04296+3429 and IRAS 05341+0852: Spatial Extent of Hydrocarbon Dust Emission and Dust Evolutionary Sequence*

We present 3 μm spectroscopy of the carbon-rich protoplanetary nebulae IRAS 04296+3429 and IRAS 05341+0852, conducted with the adaptive optics system at the Subaru Telescope. We utilize the nearly diffraction-limited spectroscopy to probe the spatial extent of the hydrocarbon dust emitting zone. We find a hydrocarbon emission core extending up to 100-160 mas from the center of IRAS 04296+3429, corresponding to a physical diameter of 400-640 AU, assuming a distance of 4 kpc. However, we find that IRAS 05341+0852 is not spatially resolved with this instrumentation. The physical extent of these protoplanetary nebulae, along with the reanalyzed data of IRAS 22272+5435 published previously, suggests a correlation between the physical extent of the hydrocarbon dust emission and the spectral evolution of the aliphatic to aromatic features in these post-AGB stars. These measurements represent the first direct test of the proposed chemical synthesis route of carbonaceous dust in the circumstellar environment of evolved stars.

Carbon Isotope Ratio in 12CO/13CO toward Local Molecular Clouds with Near-Infrared High-Resolution Spectroscopy of Vibrational Transition Bands

We report the carbon monoxide isotope ratio in local molecular clouds toward LkHα 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of 12CO ν = 2 ← 0 and 13CO ν = 1 ← 0 were observed with high-resolution near-infrared spectroscopy (R = 23,000) to measure the 12CO/13CO ratio. The isotopic ratios are 12CO/13CO = 137 ± 9 (LkHα 101), 86 ± 49 (AFGL 490), and 158 (Mon R2 IRS 3), which are 1.5-2.8 times higher than the local interstellar medium value of 12CO/13CO = 57 ± 5 from millimeter C18O emission observations. This is not easily explained by saturation of the 13CO absorption. It is also questionable whether the selective photodestruction of 13CO can account for the difference between the Galactic trend and the present observation, because the molecular clouds are with high visible extinction (AV = 10-70 mag), well shielded from destructive FUV radiation. The molecular gas associated with AFGL 490 and Mon R2 IRS 3 consists of multiple temperature components lying in the lines of sight. In the cool component (Tex < 100 K), the excitation temperature of 12CO is twice that of 13CO. We attribute the temperature discrepancy to the photon-trapping effect, which makes the radiative cooling of the main isotopomer less effective.

FAST [Fe II]?Wind with a Wide Opening Angle from L1551?IRS?5*

We present new velocity-resolved spectra of the [Fe II] λ1.644 μm line emission toward the L1551 IRS 5 outflow. The spectra were taken toward the bright [Fe II] knots PHK 1 and PHK 2 with the slit positions perpendicular to the northern jet. We have two major conclusions: (1) At PHK 1, located 12 away from the L1551 IRS 5 VLA sources, the spatial profile of the low radial velocity component at VLSR ~ -110 km s-1 shows two spatial subcomponents with their FWHMs of 083 and 284. The wide subcomponent has an wide opening angle of ~100°, which is consistent with the opening angle suggested by the broad velocity width of the narrow one. It favors the interpretation that both subcomponents of the low-velocity component arise from the same outflow. The gas corresponding to the wide subcomponent fills the space between the optical jet and the shell of the CO molecular outflow and may be sweeping up envelope material in the vicinity of the protostars. (2) At PHK 2, located ~42 away from the VLA sources, we confirmed that the northern jet has two radial velocity components: VLSR ~ -270 and -140 km s-1. The former velocity component is highly collimated because it has the same spatial width of 078 at both of the two [Fe II] knots.

First Detection of Na I D Lines in High-Redshift Damped Lyα Systems*

An NIR (1.18–1.35 � m) high-resolution spectrum of the gravitationally lensed QSO APM 08279+5255 was obtained with the Subaru Telescope IRCS using the AO system. We have detected strong Na i D kk5891, 5897 doublet absorption in high-redshift DLAs at zabs ¼ 1:062 and 1.181, confirming the presence of Na i ,w hich was firstreportedfortherest-frameUVNaikk3303.3,3303.9doubletbyPetitjeanetal.ThisisthefirstdetectionofNa i D absorption in a high-redshift (z > 1)DLA. We have also detected a new Nai component in thezabs ¼ 1:062DLA and four new components in the zabs ¼ 1:181 DLA. Using an empirical relationship between Na i and H i column density,wefoundthatallcomponentshavelargeHicolumndensity( logNH i ½cm � 2 � k20:3),soeachcomponentis classified as DLA absorption. We also detected strong Na i D absorption associated with a Mg ii system at zabs ¼ 1:173. Because no other metal absorption lines were detected in this system at the velocity of the Na i absorption in previously reported optical spectra, we infer that this Na i absorption cloud probably appeared in the line of sight toward the QSO after the optical observation. This newly found cloud is likely to be a DLA based on its large estimated H i column density. We found that the NNa i/NCa ii ratios in these DLAs are systematically smaller than those observed in the Galaxy; they are more consistent with the ratios seen in the LMC. This is consistent with dust depletion generally being smaller in lower metallicity environments. However, all five clouds of the zabs ¼ 1:181 system have a high NNa i/NCa ii ratio, which is characteristic of cold dense gas. We tentatively suggest that the host galaxy of this system may be the most significant contributor to the gravitational lens toward APM 08279+5255. Subject headings: galaxies: formation — gravitational lensing — intergalactic medium — quasars: absorption lines — quasars: individual (APM 08279+5255)

Performance update of the infrared camera and spectrograph for the Subaru Telescope (IRCS)

We present the upgraded performance of the Infrared Camera and Spectrograph for the Subaru Telescope (IRCS). The IRCS has been very successfully operating on cassegrain focus of the telescope about four years after the first light in February 2000. Initially the capability of the IRCS was limited due to the quite low sensitivity of the camera side array (Q.E.~50%) and the high dark current (~0.6e-/sec) of the spectrograph side array. To improve the performance, two major upgrades were carried out for the IRCS in these four years. The first major upgrade was the replacement of the previous engineering grade Aladdin-II array on the camera side used for imaging and grism spectroscopy into the new Aladdin-III array with significantly improved sensitivity (Q.E.~95%) in August 2001. Then, we also replaced the previous Aladdin-II array on the spectrograph side for high dispersion echelle spectroscopy into the new Aladdin-III array with good sensitivity (Q.E.~95%) and low dark current (~0.05e-/s) in the second major upgrade in June 2003. In this report, we will show the updated characteristics for the new Aladdin-III on the spectrograph side and also summarise the total performance of the IRCS after the upgrades together with actually achieved scientific results.

A SUBARCSECOND COMPANION TO THE T TAURI STAR AS 353B

Adaptive optics imaging of the bright visual T Tauri binary AS 353 with the Subaru Telescope shows that it is a hierarchical triple system. The secondary component, located 56 south of AS 353A, is resolved into a subarcsecond binary, AS 353 Ba and Bb, separated by 024. Resolved spectroscopy of the two close components shows that both have nearly identical spectral types of about M1.5. Whereas AS 353A and Ba show clear evidence of an infrared excess, AS 353 Bb does not. We discuss the possible role of multiplicity in launching the large Herbig-Haro flow associated with AS 353A.