71 research outputs found
New 60-cm Radio Survey Telescope with the Sideband-Separating SIS Receiver for the 200 GHz Band
We have upgraded the 60-cm radio survey telescope located in Nobeyama, Japan.
We developed a new waveguide-type sideband-separating SIS mixer for the
telescope, which enables the simultaneous detection of distinct molecular
emission lines both in the upper and lower sidebands. Over the RF frequency
range of 205-240 GHz, the single-sideband receiver noise temperatures of the
new mixer are 40-100 K for the 4.0-8.0 GHz IF frequency band. The image
rejection ratios are greater than 10 dB over the same range. For the dual IF
signals obtained by the receiver, we have developed two sets of acousto-optical
spectrometers and a telescope control system. Using the new telescope system,
we successfully detected the 12CO (J=2-1) and 13CO (J=2-1) emission lines
simultaneously toward Orion KL in 2005 March. Using the waveguide-type
sideband-separating SIS mixer for the 200 GHz band, we have initiated the first
simultaneous 12CO (J=2-1) and 13CO (J=2-1) survey of the galactic plane as well
as large-scale mapping observations of nearby molecular clouds.Comment: 15 pages, 15 figures, Accepted for publication in PASJ, version with
high resolution figures is available via
http://www.nro.nao.ac.jp/~nakajima/vst1_2sb.pd
The AMANOGAWA-2SB Galactic Plane Survey I: Data on the Galactic Equator
Using a waveguide-type sideband-separating receiver (2SB receiver) on the
Tokyo-NRO 60-cm telescope (renamed the AMANOGAWA telescope), we carried out
simultaneous observations in the 12CO(J = 2-1) and 13CO(J = 2-1) lines over the
Galactic plane l = 10-245 deg along b = 0 deg with a 3.75 arcmin grid. Using
the 12CO(J = 1-0) data of Dame et al. (2001), who used a beam size almost the
same as ours, we show 12CO(J = 2-1)/12CO(J = 1-0) and 13CO(J = 2-1)/12CO(J =
2-1) intensity ratios on the l-v map and the intensity correlations among the
three lines. As a result, a linear correlation between 12CO(J = 1-0) and 12CO(J
= 2-1) and a curve correlation between 12CO(J = 2-1) and 13CO(J = 2-1), as
produced by most of the data, are found. We investigate these correlations with
simple radiative transfer equations to ascertain a number of restrictions on
the physical quantities of molecular gas on a galactic scale.Comment: 22 pages, 13 figures, accepted for publication in PAS
Search for Outer Massive Bodies around Transiting Planetary Systems: Candidates of Faint Stellar Companions around HAT-P-7
We present results of direct imaging observations for HAT-P-7 taken with the
Subaru HiCIAO and the Calar Alto AstraLux. Since the close-in transiting planet
HAT-P-7b was reported to have a highly tilted orbit, massive bodies such as
giant planets, brown dwarfs, or a binary star are expected to exist in the
outer region of this system. We show that there are indeed two candidates for
distant faint stellar companions around HAT-P-7. We discuss possible roles
played by such companions on the orbital evolution of HAT-P-7b. We conclude
that as there is a third body in the system as reported by Winn et al. (2009,
ApJL, 763, L99), the Kozai migration is less likely while planet-planet
scattering is possible.Comment: 8 pages, 3 figures, 2 tables, PASJ in pres
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
Polarimetric Imaging of Large Cavity Structures in the Pre-transitional Protoplanetary Disk around PDS 70: Observations of the disk
We present high resolution H-band polarized intensity (PI; FWHM = 0."1: 14
AU) and L'-band imaging data (FWHM = 0."11: 15 AU) of the circumstellar disk
around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of
28 AU (0."2) up to 210 AU (1."5). In both images, a giant inner gap is clearly
resolved for the first time, and the radius of the gap is ~70 AU. Our data show
that the geometric center of the disk shifts by ~6 AU toward the minor axis. We
confirm that the brown dwarf companion candidate to the north of PDS 70 is a
background star based on its proper motion. As a result of SED fitting by Monte
Carlo radiative transfer modeling, we infer the existence of an optically thick
inner disk at a few AU. Combining our observations and modeling, we classify
the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the
analysis of L'-band imaging data, we put an upper limit mass of companions at
~30 to ~50MJ within the gap. Taking account of the presence of the large and
sharp gap, we suggest that the gap could be formed by dynamical interactions of
sub-stellar companions or multiple unseen giant planets in the gap.Comment: accepted by APJ
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