199 research outputs found
Evidence that the Occurrence Rate of Hot Jupiters around Sun-like Stars Decreases with Stellar Age
We investigate how the occurrence rate of giant planets (minimum mass ) around Sun-like stars depends on the age, mass, and
metallicity of their host stars. We develop a hierarchical Bayesian framework
to infer the number of planets per star (NPPS) as a function of both planetary
and stellar parameters. The framework fully takes into account the
uncertainties in the latter by utilizing the posterior samples for the stellar
parameters obtained by fitting stellar isochrone models to the spectroscopic
parameters, Gaia DR3 parallaxes, and 2MASS -band magnitudes adopting
a certain bookkeeping prior. We apply the framework to 46 Doppler giants found
around a sample of 382 Sun-like stars from the California Legacy Survey catalog
that publishes spectroscopic parameters and search completeness for all the
surveyed stars. We find evidence that the NPPS of hot Jupiters (orbital period
-) decreases roughly in the latter half of the main
sequence over the timescale of , while that of cold
Jupiters (-) does not. Assuming that this decrease is
real and caused by tidal orbital decay, the modified stellar tidal quality
factor is implied to be for a Sun-like
main-sequence star orbited by a Jupiter-mass planet with .Comment: Accepted by the Astronomical Journal, 19 pages, 11 figure
OGLE-2013-BLG-0911Lb: A Secondary on the Brown-dwarf Planet Boundary around an M Dwarf
We present the analysis of the binary-lens microlensing event OGLE-2013-BLG-0911. The best-fit solutions indicate the binary mass ratio of q 0.03, which differs from that reported in Shvartzvald et al. The event suffers from the well-known close/wide degeneracy, resulting in two groups of solutions for the projected separation normalized by the Einstein radius of s ~ 0.15 or s ~ 7. The finite source and the parallax observations allow us to measure the lens physical parameters. The lens system is an M dwarf orbited by a massive Jupiter companion at very close (M_(host) = 0.30^(+0.08)_(-0.06)M⊙, M_(comp) = 10.1^(+2.9)_(-2.2)M_(Jup), a_(exp) = 0.40^(+0.05)_(-0.04) au) or wide (M_(host) = 0.28^(+0.10)_(-0.08) M⊙, M_(comp) = 9.9^(+3.8)_(-3.5)M_(Jup), a(exp) = 18.0^(+3.8)_(3.5) au) separation. Although the mass ratio is slightly above the planet-brown dwarf (BD) mass-ratio boundary of q = 0.03, which is generally used, the median physical mass of the companion is slightly below the planet-BD mass boundary of 13M_(Jup). It is likely that the formation mechanisms for BDs and planets are different and the objects near the boundaries could have been formed by either mechanism. It is important to probe the distribution of such companions with masses of ~13M_(Jup) in order to statistically constrain the formation theories for both BDs and massive planets. In particular, the microlensing method is able to probe the distribution around low-mass M dwarfs and even BDs, which is challenging for other exoplanet detection methods
OGLE-2013-BLG-0911Lb: A Secondary on the Brown-dwarf Planet Boundary around an M Dwarf
We present the analysis of the binary-lens microlensing event OGLE-2013-BLG-0911. The best-fit solutions indicate the binary mass ratio of q 0.03, which differs from that reported in Shvartzvald et al. The event suffers from the well-known close/wide degeneracy, resulting in two groups of solutions for the projected separation normalized by the Einstein radius of s ~ 0.15 or s ~ 7. The finite source and the parallax observations allow us to measure the lens physical parameters. The lens system is an M dwarf orbited by a massive Jupiter companion at very close (M_(host) = 0.30^(+0.08)_(-0.06)M⊙, M_(comp) = 10.1^(+2.9)_(-2.2)M_(Jup), a_(exp) = 0.40^(+0.05)_(-0.04) au) or wide (M_(host) = 0.28^(+0.10)_(-0.08) M⊙, M_(comp) = 9.9^(+3.8)_(-3.5)M_(Jup), a(exp) = 18.0^(+3.8)_(3.5) au) separation. Although the mass ratio is slightly above the planet-brown dwarf (BD) mass-ratio boundary of q = 0.03, which is generally used, the median physical mass of the companion is slightly below the planet-BD mass boundary of 13M_(Jup). It is likely that the formation mechanisms for BDs and planets are different and the objects near the boundaries could have been formed by either mechanism. It is important to probe the distribution of such companions with masses of ~13M_(Jup) in order to statistically constrain the formation theories for both BDs and massive planets. In particular, the microlensing method is able to probe the distribution around low-mass M dwarfs and even BDs, which is challenging for other exoplanet detection methods
Ab initio calculation for electronic structure and optical property of tungsten carbide in a TiCN-based cermet for solar thermal applications
We present an ab initio calculation to understand electronic structures and
optical properties of a tungsten carbide WC being a major component of a
TiCN-based cermet. We found that the WC has a fairly low-energy plasma
excitation 0.6 eV (2 m) and therefore can be a good constituent of a
solar selective absorber. The evaluated figure of merit for photothermal
conversion is prominently high compared to those of the other materials
included in the TiCN-based cermet. The imaginary part of the dielectric
function is considerably small around the zero point of the real part of the
dielectric function, corresponding to the plasma excitation energy. Therefore,
a clear plasma edge appeared, ensuring the high performance of the WC as the
solar absorber.Comment: 13pages, 8 figures, 2table
Revealing Short-period Exoplanets and Brown Dwarfs in the Galactic Bulge using the Microlensing Xallarap Effect with the \textit{Nancy Grace Roman Space Telescope}
The \textit{Nancy Grace Roman Space Telescope} (\textit{ Roman}) will provide
an enormous number of microlensing light curves with much better photometric
precisions than ongoing ground-based observations. Such light curves will
enable us to observe high-order microlensing effects which have been previously
difficult to detect. In this paper, we investigate \textit{Roman}'s potential
to detect and characterize short-period planets and brown dwarfs (BDs) in
source systems using the orbital motion of source stars, the so-called xallarap
effect. We analytically estimate the measurement uncertainties of xallarap
parameters using the Fisher matrix analysis. We show that the \textit{Roman}
Galactic Exoplanet Survey (RGES) can detect warm Jupiters with masses down to
0.5 and orbital period of 30 days via the xallarap effect.
Assuming a planetary frequency function from \citet{Cumming+2008}, we find
\textit{Roman} will detect hot and warm Jupiters and close-in
BDs around microlensed source stars during the microlensing survey. These
detections are likely to be accompanied by the measurements of the companion's
masses and orbital elements, which will aid in the study of the physical
properties for close-in planet and BD populations in the Galactic bulge.Comment: Accepted for publication in The Astronomical Journa
Distinction of synthetic dl-α-tocopherol from natural vitamin E (d-α-tocopherol) by reversed-phase liquid chromatography. Enhanced selectivity of a polymeric C18 stationary phase at low temperature and/or at high pressure
© 2016 Elsevier B.V. Separation of diastereomers of DL-α-tocopherol was studied by reversed-phase liquid chromatography using three types of stationary phases, polymeric ODS, polymeric C30, and monomeric ODS. Polymeric ODS stationary phase (Inertsil ODS-P, 3 mmID, 20 cm) was effective for the separation of the isomers created by the presence of three chiral centers on the alkyl chain of synthetic DL-α-tocopherol. Considerable improvement of the separation of isomers was observed on ODS-P phase at high pressure and at low temperature. Complete separation of four pairs of diastereomers was achieved at 12.0 °C, 536 bar, while three peaks were observed when the separation was carried out either at 12.0 °C at low pressure or at 20 °C at 488 bar. Higher temperature (30.0 °C) with the ODS-P phase resulted in only partial separation of the diastereomers even at high pressure. Only slight resolution was observed for the mixture of diastereomers with the C30 stationary phase (Inertsil C30) at 12.0 °C and 441 bar, although the stationary phase afforded greater resolution for β- and γ-tocopherol than ODS-P. A monomeric C18 stationary phase did not show any separation at 12.0 °C and 463 bar. The results suggest that the binding site of the polymeric ODS-P phase is selective for flexible alkyl chains that provided the longest retention for the natural form, (R,R,R) form, and the enantiomer, (S,S,S) form, of DL-α-tocopherol
A comparative profile of urinary scent signals of two endangered Japanese populations of leopard cat
Two subspecies of mainland leopard cats (Prionailurus bengalensis), Iriomote cats (Prionailurus bengalensis iriomotensis), and Tsushima leopard cats (Prionailurus bengalensis euptilurus), are small, endangered felids that are endemic to the Japanese islands, Iriomote-jima and Tsushima, respectively. Both subspecies have an estimated population size of only about 100 individuals each. Therefore, it is crucial to expand our understanding of these subspecies to successfully conserve them. While their morphology, anatomy, ecology, pathology, and genetics are well studied, little is known about their physiology regulated in subspecies-specific manners. This study characterized their urinary volatile and nonvolatile organic compounds, with which individuals express their physiological status and territorial ownership. We found significantly higher levels of 3-mercapto-3-methyl-1-butanol and its structural analogs, which are scent signals of domestic cats, in the urinary headspace of Iriomote cats than in that of Tsushima leopard cats. There were no differences in the urinary levels of felinine, an amino acid that acts as a precursor of 3-mercapto-3-methyl-1-butanol, suggesting the variation of catalytic activities for decomposing felinine to 3-mercapto-3-methyl-1-butanol between subspecies. Both subspecies exhibited physiological proteinuria due to the secretion of carboxylesterase 5A, also known as cauxin, for the production of felinine. In conclusion, while the two endangered Japanese subspecies of mainland leopard cats share similar genetic backgrounds, urinary contents of metabolites vary between the subspecies. We suggest that after the separation into two subspecies, the regulation of the metabolic pathway for 3-mercapto-3-methyl-1-butanol production likely evolved differently in each subspecies in response to their specific environments
Microlensing Results Challenge the Core Accretion Runaway Growth Scenario for Gas Giants
We compare the planet-to-star mass-ratio distribution measured by
gravitational microlensing to core accretion theory predictions from population
synthesis models. The core accretion theory's runaway gas accretion process
predicts a dearth of intermediate-mass giant planets that is not seen in the
microlensing results. In particular, the models predict fewer
planets at mass ratios of than inferred
from microlensing observations. This tension implies that gas giant formation
may involve processes that have hitherto been overlooked by existing core
accretion models or that the planet-forming environment varies considerably as
a function of host-star mass. Variation from the usual assumptions for the
protoplanetary disk viscosity and thickness could reduce this discrepancy, but
such changes might conflict with microlensing results at larger or smaller mass
ratios, or with other observations. The resolution of this discrepancy may have
important implications for planetary habitability because it has been suggested
that the runaway gas accretion process may have triggered the delivery of water
to our inner solar system. So, an understanding of giant planet formation may
help us to determine the occurrence rate of habitable planets.Comment: 12 pages, 2 figures, 1 table, accepted for publication in ApJ
Ultra-broadband surface-normal coherent optical receiver with nanometallic polarizers
A coherent receiver that can demodulate high-speed in-phase and quadrature
signals of light is an essential component for optical communication,
interconnects, imaging, and computing. Conventional waveguide-based coherent
receivers, however, exhibit large footprints, difficulty in coupling a large
number of spatial channels efficiently, and limited operating bandwidth imposed
by the waveguide-based optical hybrid. Here, we present a surface-normal
coherent receiver with nanometallic-grating-based polarizers integrated
directly on top of photodetectors without the need for an optical hybrid
circuit. Using a fabricated device with the active section occupying a
70-{\mu}m-square footprint, we demonstrate demodulation of high-speed (up to 64
Gbaud) coherent signals in various formats. Moreover, ultra-broadband operation
from 1260 nm to 1630 nm is demonstrated, thanks to the wavelength-insensitive
nanometallic polarizers. To our knowledge, this is the first demonstration of a
surface-normal homodyne optical receiver, which can easily be scaled to a
compact two-dimensional arrayed device to receive highly parallelized coherent
signals.Comment: 23 pages, 4 figures (main manuscript) + 4 pages, 2 figures
(supporting info
Subaru Hyper Suprime-Cam Survey for An Optical Counterpart of GW170817
We perform a -band survey for an optical counterpart of a binary neutron
star coalescence GW170817 with Subaru/Hyper Suprime-Cam. Our untargeted
transient search covers deg corresponding to the credible
region of GW170817 and reaches the completeness magnitude of mag
on average. As a result, we find 60 candidates of extragalactic transients,
including J-GEM17btc (a.k.a. SSS17a/DLT17ck). While J-GEM17btc is associated
with NGC 4993 that is firmly located inside the 3D skymap of GW170817, the
other 59 candidates do not have distance information in the GLADE v2 catalog or
NASA/IPAC Extragalactic Database (NED). Among 59 candidates, 58 are located at
the center of extended objects in the Pan-STARRS1 catalog, while one candidate
has an offset. We present location, -band apparent magnitude, and time
variability of the candidates and evaluate the probabilities that they are
located inside of the 3D skymap of GW170817. The probability for J-GEM17btc is
being much higher than those for the other 59 candidates
(). Furthermore, the possibility, that at
least one of the other 59 candidates is located within the 3D skymap, is only
. Therefore, we conclude that J-GEM17btc is the most-likely and
distinguished candidate as the optical counterpart of GW170817.Comment: 14 pages, 9 figures. Accepted for publication in PASJ (Publications
of the Astronomical Society of Japan
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