A5041829969- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Astro and Planetary Science
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Calibration and Measurement Techniques
- Spectroscopy and Laser Applications
- Adaptive optics and wavefront sensing
- Advanced Fiber Laser Technologies
- Solid State Laser Technologies
- Computational Physics and Python Applications
- Advanced Fiber Optic Sensors
- Space Exploration and Technology
- Solar and Space Plasma Dynamics
- Scientific Research and Discoveries
- Astrophysical Phenomena and Observations
- Planetary Science and Exploration
- Geophysics and Gravity Measurements
Tokyo Institute of Technology
2007-2024
National Astronomical Observatory of Japan
2004-2008
Kobe University
2005-2008
National Institutes of Natural Sciences
2005
Tokyo University of Science
2004
The University of Tokyo
2004
Doppler measurements from Subaru and Keck have revealed radial velocity variations in the V=8.15, G0IV star HD 149026 consistent with a Saturn-Mass planet 2.8766 day orbit. Photometric observations at Fairborn Observatory detected three complete transit events depths of 0.003 mag predicted times conjunction. is now second brightest transiting extrasolar planet. The mass star, based on interpolation stellar evolutionary models, 1.3 +/- 0.1 solar masses; together amplitude, K=43.3 m s^-1, we...
Using small automated telescopes in Arizona and Hawaii, the HATNet project has detected an object transiting one member of double star system ADS 16402 AB. This is a pair G0 main-sequence stars with age about 3 Gyr at distance ~139 pc projected separation ~1550 AU. The transit signal period 4.46529 days depth 0.015 mag. From follow-up photometry spectroscopy, we find that "hot Jupiter" planet mass 0.53 M_jup radius ~1.36 R_jup traveling orbit semimajor axis 0.055 AU inclination 85.9 deg,...
We report the detection of five Jovian-mass planets orbiting high-metallicity stars. Four these stars were first observed as part N2K program, and exhibited low rms velocity scatter after three consecutive observations. However, follow-up observations over last 3 years now reveal presence longer period with orbital periods ranging from 21 days to a few years. HD 11506 is G0 V star planet M sin i = 4.74 MJup in 3.85 yr orbit. 17156 3.12 21.2 day The eccentricity this orbit 0.67, one highest...
Detailed chemical analyses of M dwarfs are scarce but necessary to constrain the formation environment and internal structure planets being found around them. We present elemental abundances 13 (2900 < Teff 3500 K) observed in Subaru/IRD planet search project. They mid-to-late whose abundance individual elements has not been well studied. use high-resolution (~70,000) near-infrared (970-1750 nm) spectra measure Na, Mg, Si, K, Ca, Ti, V, Cr, Mn, Fe, Sr by line-by-line analysis based on model...
We report the discovery of two new transiting extrasolar planets. HAT-P-18b orbits V = 12.759 K2 dwarf star GSC 2594−00646, with a period P 5.508023 ± 0.000006 days, transit epoch Tc 2454715.02174 0.00020 (BJD), and duration 0.1131 0.0009 days. The host has mass 0.77 0.03 M☉, radius 0.75 0.04 R☉, effective temperature 4803 80 K, metallicity [Fe/H] +0.10 0.08. planetary companion 0.197 0.013 MJ 0.995 0.052 RJ, yielding mean density 0.25 g cm−3. HAT-P-19b 12.901 K1 2283−00589, 4.008778...
We report the detection of two short-period planets discovered at Keck Observatory. HD 149143 is a metal-rich G0 IV star with planet M sin i = 1.33MJ and an orbital radius 0.053 AU. The best-fit Keplerian model has period, P 4.072 days, semivelocity amplitude, K 149.6 m s-1, eccentricity, e 0.016 ± 0.01. host chromospherically inactive metal-rich, [Fe/H] 0.26. Based on Teff stellar luminosity, we derive 1.49 R☉. Photometric observations were carried out using automated photometric telescopes...
We present an improved measurement of the Rossiter-McLaughlin effect for exoplanetary system HD 17156, based on radial-velocity data gathered with Subaru 8.2m telescope throughout planetary transit UT 2008 November 7. The allow a precise and independent determination projected spin-orbit angle this system: $\lambda = 10.0^{\circ} \pm 5.1^{\circ}$. This result supersedes previous claim 62^{\circ} 25^{\circ}$ by Narita et al., which was lower-precision poor statistics. Thus stellar spin...
We report the detections of two substellar companions orbiting around evolved intermediate-mass stars from precise Doppler measurements at Subaru Telescope and Okayama Astrophysical Observatory. HD 145457 is a K0 giant with mass 1.9 M_sun has planet minimum m_2sini=2.9 M_J period P=176 d eccentricity e=0.11. 180314 also 2.6 hosts companion m_2sin i=22 M_J, which falls in brown-dwarf regime, an orbit P=396 e=0.26. b one innermost planets seventh candidate brown-dwarf-mass found stars.
We have obtained high-resolution (R ≃ 50,000 or 90,000), high-quality (S/N ≳ 100) spectra of 22 very metal-poor stars ([Fe/H] ≲ -2.5) with the High Dispersion Spectrograph fabricated for 8.2 m Subaru Telescope. The cover wavelength range from 3500 to 5100 Å; equivalent widths are measured isolated lines numerous elemental species, including α-elements, iron-peak elements, and light heavy neutron-capture elements. Errors in measurements comparisons previous studies discussed. These data will...
Abstract We present three-dimensional (3D) maps of Jupiter’s atmospheric circulation at cloud-top level from Doppler-imaging data obtained in the visible domain with JIVE, second node JOVIAL network, which is mounted on Dunn Solar Telescope Sunspot, New Mexico. report 12 nights observations between 2018 May 4 and 30, representing a total about 80 hr. First, average zonal wind profile derived our compatible that cloud-tracking measurements performed Hubble Space images April Outer Planet...
We report the discovery of two exoplanets around M dwarfs GJ 724 and 3988 using radial velocity (RV) method. obtained a total 153 3.5 m Calar Alto/CARMENES spectra for both targets measured their RVs activity indicators. also added archival ESO/HARPS data infrared RV measurements from Subaru/IRD 3988. searched periodic stable signals to subsequently construct Keplerian models, considering different numbers planets, we selected best models based on Bayesian evidence. Gaussian process (GP)...
We have determined the isotopic abundance ratio of 7Li/6Li in interstellar media (ISMs) along lines sight to HD169454 and HD250290 using High-Dispersion Spectrograph on Subaru Telescope. also observed ζ Oph for comparison with previous data. The ratios were = 8.1+3.6−1.8 6.3+3.0−1.7 HD250290, respectively. These values are reasonable agreement those previously solar neighborhood ISMs within ±2σ error bars consistent our measurement 7.1+2.9−1.6 a cloud line Oph. This is good evidence...
Balmer and Paschen continuum emission, as well series lines of P Cygni-type profile from Hγ through H23, are revealed in the violet spectra BM Gem, a carbon star associated with an oxygen-rich circumstellar shell ("silicate star"). The blueshifted absorption indicates presence outflow, line-of-sight velocity which is at least 400 km s−1. show significant change over period 75 days. We argue that observed unusual features Gem strong evidence for companion, should form accretion disk gives...
Abstract We present the optical spectra of 338 nearby M dwarfs, and compute their spectral types, effective temperatures (Teff), radii. Our were obtained using several spectrometers with resolutions that range from 1200 to 10000. As many as 97% observed M-type dwarfs have a type M3–M6, typical error 0.4 subtype, among which types M4–M5 are most common. infer Teff our sample by fitting theoretical PHOENIX model. inferred is calibrated whose been well determined calibrations supported previous...
Procyon A is a bright F5IV star in binary system. Although the distance, mass and angular diameter of this are all known with high precision, exact evolutionary state still unclear. Evolutionary tracks different ages fractions hydrogen core pass, within errors, through observed position Hertzsprung-Russell diagram. For more than15 years several groups have studied solar-like oscillations to determine its state. studies independently detected power excess periodogram, there no agreement on...
We have carried out a precise Doppler survey of G-type giants aiming to unveil the properties planetary systems in intermediate-mass stars (<TEX>$1.5-5M_{\bigodot}$</TEX>). are promising targets for planet searches around massive stars, because they slow-rotators and many sharp absorption lines their spectra surface activities relatively low contrast younger counterparts on main-sequence (B-A stars). now monitoring radial velocities about 300 late (including early K-type) using HIgh...
Because of their large numbers, red dwarfs may be the most abundant planet hosts in our Galaxy. In order to detect Earth-like planets around nearby (in particular late-M stars), it is crucial conduct precise radial velocity (RV) measurements at near-infrared wavelengths where these stars emit light. We report development Infrared Doppler (IRD) spectrometer for Subaru telescope. IRD a fiber-fed, high-precision, near infrared with spectral resolution R~70,000 covering from 0.97 1.75 μm. To...