311 research outputs found
Investigation of evolution strategy and optimization of induction heating model
An optimal design method using the finite element method and the evolution strategy (ES) is investigated. The evolution strategy is applied to the optimization of induction heating model. The position of auxiliary coil, frequency and ampere-turns are optimized so that the distribution of eddy current density on the surface of steel becomes uniform. It is shown that the selection of the appropriate parameter is important in the practical application of ES</p
Gifts from Exoplanetary Transits
The discovery of transiting extrasolar planets has enabled us a number of
interesting stduies. Transit photometry reveals the radius and the orbital
inclination of transiting planets, and thereby we can learn the true mass and
the density of respective planets by the combined information of radial
velocity measurements. In addition, follow-up observations of transiting
planets such as secondary eclipse, transit timing variations, transmission
spectroscopy, and the Rossiter-McLaughlin effect provide us information of
their dayside temperature, unseen bodies in systems, planetary atmospheres, and
obliquity of planetary orbits. Such observational information, which will
provide us a greater understanding of extrasolar planets, is available only for
transiting planets. Here I briefly summarize what we can learn from transiting
planets and introduce previous studies.Comment: 6 pages, 2 figures, Proceedings of the 2nd Subaru International
Conference "Exoplanets and Disks: Their Formation and Diversity" Keauhou -
Hawaii - USA, 9-12 March 200
First Evidence of a Retrograde Orbit of Transiting Exoplanet HAT-P-7b
We present the first evidence of a retrograde orbit of the transiting
exoplanet HAT-P-7b. The discovery is based on a measurement of the
Rossiter-McLaughlin effect with the Subaru HDS during a transit of HAT-P-7b,
which occurred on UT 2008 May 30. Our best-fit model shows that the spin-orbit
alignment angle of this planet is \lambda = -132.6 (+10.5, -16.3) degrees. The
existence of such a retrograde planet have been predicted by recent planetary
migration models considering planet-planet scattering processes or the Kozai
migration. Our finding provides an important milestone that supports such
dynamic migration theories.Comment: PASJ Letters, in press [13 pages
Spin-Orbit Alignment of the TrES-4 Transiting Planetary System and Possible Additional Radial Velocity Variation
We report new radial velocities of the TrES-4 transiting planetary system,
including observations of a full transit, with the High Dispersion Spectrograph
of the Subaru 8.2m telescope. Modeling of the Rossiter-McLaughlin effect
indicates that TrES-4b has closely aligned orbital and stellar spin axes, with
. The close spin-orbit alignment angle
of TrES-4b seems to argue against a migration history involving planet-planet
scattering or Kozai cycles, although there are two nearby faint stars that
could be binary companion candidates. Comparison of our out-of-transit data
from 4 different runs suggest that the star exhibits radial velocity
variability of 20 ms^-1 in excess of a single Keplerian orbit. Although
the cause of the excess radial velocity variability is unknown, we discuss
various possibilities including systematic measurement errors, starspots or
other intrinsic motions, and additional companions besides the transiting
planet.Comment: 10 pages, 3 figures, 3 tables, PASJ in pres
Analytic Description of the Rossiter-McLaughlin Effect for Transiting Exoplanets: Cross-Correlation Method and Comparison with Simulated Data
We obtain analytical expressions for the velocity anomaly due to the
Rossiter- McLaughlin effect, for the case when the anomalous radial velocity is
obtained by cross-correlation with a stellar template spectrum. In the limit of
vanishing width of the stellar absorption lines, our result reduces to the
formula derived by Ohta et al. (2005), which is based on the first moment of
distorted stellar lines. Our new formula contains a term dependent on the
stellar linewidth, which becomes important when rotational line broadening is
appreciable. We generate mock transit spectra for four existing exoplanetary
systems (HD17156, TrES-2, TrES- 4, and HD209458) following the procedure of
Winn et al. (2005), and find that the new formula is in better agreement with
the velocity anomaly extracted from the mock data. Thus, our result provides a
more reliable analytical description of the velocity anomaly due to the
Rossiter-McLaughlin effect, and explains the previously observed dependence of
the velocity anomaly on the stellar rotation velocity.Comment: 31 pages, 9 figures, Astrophysical Journal in pres
Measurements of Stellar Inclinations for Kepler Planet Candidates II: Candidate Spin-Orbit Misalignments in Single and Multiple-Transiting Systems
We present a test for spin-orbit alignment for the host stars of 25 candidate
planetary systems detected by the {\it Kepler} spacecraft. The inclination
angle of each star's rotation axis was estimated from its rotation period,
rotational line broadening, and radius. The rotation periods were determined
using the {\it Kepler} photometric time series. The rotational line broadening
was determined from high-resolution optical spectra with Subaru/HDS. Those same
spectra were used to determine the star's photospheric parameters (effective
temperature, surface gravity, metallicity) which were then interpreted with
stellar-evolutionary models to determine stellar radii. We combine the new
sample with the 7 stars from our previous work on this subject, finding that
the stars show a statistical tendency to have inclinations near 90, in
alignment with the planetary orbits. Possible spin-orbit misalignments are seen
in several systems, including three multiple-planet systems (KOI-304, 988,
2261). Ideally these systems should be scrutinized with complementary
techniques---such as the Rossiter-McLaughlin effect, starspot-crossing
anomalies or asteroseismology---but the measurements will be difficult owing to
the relatively faint apparent magnitudes and small transit signals in these
systems.Comment: 11 pages, 9 figures, accepted for publication in Ap
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