155 research outputs found
Near-Infrared Imaging Polarimetry of Inner Region of GG Tau A Disk
By performing non-masked polarization imaging with Subaru/HiCIAO, polarized
scattered light from the inner region of the disk around the GG Tau A system
was successfully detected in the band with a spatial resolution of
approximately 0.07\arcsec, revealing the complicated inner disk structures
around this young binary. This paper reports the observation of an arc-like
structure to the north of GG Tau Ab and part of a circumstellar structure that
is noticeable around GG Tau Aa extending to a distance of approximately 28 AU
from the primary star. The speckle noise around GG Tau Ab constrains its disk
radius to <13 AU. Based on the size of the circumbinary ring and the
circumstellar disk around GG Tau Aa, the semi-major axis of the binary's orbit
is likely to be 62 AU. A comparison of the present observations with previous
ALMA and near-infrared (NIR) H emission observations suggests that the
north arc could be part of a large streamer flowing from the circumbinary ring
to sustain the circumstellar disks. According to the previous studies, the
circumstellar disk around GG Tau Aa has enough mass and can sustain itself for
a duration sufficient for planet formation; thus, our study indicates that
planets can form within close (separation 100 AU) young binary
systems.Comment: Accepted for publication in AJ, 12 pages, 5 figure
Subaru/HiCIAO imaging of LkH 330 - multi-band detection of the gap and spiral-like structures
We present - and -bands observations of the LkH 330
disk with a multi-band detection of the large gap and spiral-like structures.
The morphology of the outer disk (0\farcs3) at PA=0--45 and
PA=180--290 are likely density wave-induced spirals and comparison
between our observational results and simulations suggests a planet formation.
We have also investigated the azimuthal profiles at the ring and the outer-disk
regions as well as radial profiles in the directions of the spiral-like
structures and semi-major axis. Azimuthal analysis shows a large variety in
wavelength and implies that the disk has non-axisymmetric dust distributions.
The radial profiles in the major-axis direction (PA=) suggest that
the outer region (r\geq0\farcs25) may be influenced by shadows of the inner
region of the disk. The spiral-like directions (PA=10 and 230)
show different radial profiles, which suggests that the surfaces of the
spiral-like structures are highly flared and/or have different dust properties.
Finally, a color-map of the disk shows a lack of an outer eastern region in the
-band disk, which may hint the presence of an inner object that casts a
directional shadow onto the disk.Comment: 12pages, 16 figures, 2 tables, accepted for publication in A
Radial decoupling of small and large dust grains in the transitional disk RX J1615.3-3255
We present H-band (1.6 {\mu}m) scattered light observations of the
transitional disk RX J1615.3-3255, located in the ~1 Myr old Lupus association.
From a polarized intensity image, taken with the HiCIAO instrument of the
Subaru Telescope, we deduce the position angle and the inclination angle of the
disk. The disk is found to extend out to 68 12 AU in scattered light and
no clear structure is observed. Our inner working angle of 24 AU does not allow
us to detect a central decrease in intensity similar to that seen at 30 AU in
the 880 {\mu}m continuum observations. We compare the observations with
multiple disk models based on the Spectral Energy Distribution (SED) and submm
interferometry and find that an inner rim of the outer disk at 30 AU containing
small silicate grains produces a polarized intensity signal which is an order
of magnitude larger than observed. We show that a model in which the small dust
grains extend smoothly into the cavity found for large grains is closer to the
actual H-band observations. A comparison of models with different dust size
distributions suggests that the dust in the disk might have undergone
significant processing compared to the interstellar medium.Comment: 8 pages, 7 figures, 4 tables. Accepted for publication in A&
High-Resolution Submillimeter and Near-Infrared Studies of the Transition Disk around Sz 91
To reveal the structures of a transition disk around a young stellar object
in Lupus, Sz 91, we have performed aperture synthesis 345 GHz continuum and
CO(3--2) observations with the Submillimeter Array (\sim1\arcsec--3\arcsec
resolution), and high-resolution imaging of polarized intensity at the
-band by using the HiCIAO instrument on the Subaru Telescope (0\farcs25
resolution). Our observations successfully resolved the inner and outer radii
of the dust disk to be 65 AU and 170 AU, respectively, which indicates that Sz
91 is a transition disk source with one of the largest known inner holes. The
model fitting analysis of the spectral energy distribution reveals an H
mass of M_\sun in the cold (30 K) outer part at
AU by assuming a canonical gas-to-dust mass ratio of 100, although a
small amount ( M_\sun) of hot (180 K) dust possibly
remains inside the inner hole of the disk. The structure of the hot component
could be interpreted as either an unresolved self-luminous companion body (not
directly detected in our observations) or a narrow ring inside the inner hole.
Significant CO(3--2) emission with a velocity gradient along the major axis of
the dust disk is concentrated on the Sz 91 position, suggesting a rotating gas
disk with a radius of 420 AU. The Sz 91 disk is possibly a rare disk in an
evolutionary stage immediately after the formation of protoplanets because of
the large inner hole and the lower disk mass than other transition disks
studied thus far
A Substellar Companion to Pleiades HII 3441
We find a new substellar companion to the Pleiades member star, Pleiades HII
3441, using the Subaru telescope with adaptive optics. The discovery is made as
part of the high-contrast imaging survey to search for planetary-mass and
substellar companions in the Pleiades and young moving groups. The companion
has a projected separation of 0".49 +/- 0".02 (66 +/- 2 AU) and a mass of 68
+/- 5 M_J based on three observations in the J-, H-, and K_S-band. The spectral
type is estimated to be M7 (~2700 K), and thus no methane absorption is
detected in the H band. Our Pleiades observations result in the detection of
two substellar companions including one previously reported among 20 observed
Pleiades stars, and indicate that the fraction of substellar companions in the
Pleiades is about 10.0 +26.1/-8.8 %. This is consistent with multiplicity
studies of both the Pleiades stars and other open clusters.Comment: Main text (14 pages, 4 figures, 4 tables), and Supplementary data (8
pages, 3 tables). Accepted for Publications of Astronomical Society of Japa
Extreme Asymmetry in the Disk of V1247 Ori
We present the first near-infrared scattered-light detection of the
transitional disk around V1247 Ori, which was obtained using high-resolution
polarimetric differential imaging observations with Subaru/HiCIAO. Our imaging
in the H band reveals the disk morphology at separations of ~0.14"-0.86"
(54-330 au) from the central star. The polarized intensity (PI) image shows a
remarkable arc-like structure toward the southeast of the star, whereas the
fainter northwest region does not exhibit any notable features. The shape of
the arm is consistent with an arc of 0.28" 0.09" in radius (108 au from
the star), although the possibility of a spiral arm with a small pitch angle
cannot be excluded. V1247 Ori features an exceptionally large azimuthal
contrast in scattered, polarized light; the radial peak of the southeastern arc
is about three times brighter than the northwestern disk measured at the same
distance from the star. Combined with the previous indication of an
inhomogeneous density distribution in the gap at 46 au, the notable
asymmetry in the outer disk suggests the presence of unseen companions and/or
planet-forming processes ongoing in the arc.Comment: 21 pages, 5 figures, accepted for publication in PAS
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