A5091248458- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Planetary Science and Exploration
- Astronomy and Astrophysical Research
- Molecular Spectroscopy and Structure
- Space Satellite Systems and Control
- Space Exploration and Technology
- Fluid Dynamics Simulations and Interactions
- Solar and Space Plasma Dynamics
- Astronomical Observations and Instrumentation
- High-pressure geophysics and materials
- Granular flow and fluidized beds
- Advanced Frequency and Time Standards
- Scientific Research and Discoveries
- Particle Detector Development and Performance
- Space Science and Extraterrestrial Life
- Lattice Boltzmann Simulation Studies
- Geomagnetism and Paleomagnetism Studies
- Spacecraft and Cryogenic Technologies
- Fluid Dynamics and Heat Transfer
- Gamma-ray bursts and supernovae
- Pulsars and Gravitational Waves Research
- Microencapsulation and Drying Processes
- Spacecraft Dynamics and Control
Kurume University
2016-2022
Tokyo Institute of Technology
2002-2015
University of California, Santa Barbara
2010
University of California, Santa Cruz
2003-2005
National Astronomical Observatory of Japan
2005
Ames Research Center
2003
We have investigated the formation of close-in extrasolar giant planets through a coupling effect mutual scattering, Kozai mechanism, and tidal circularization, by orbital integrations. carried out integrations three with Jupiter-mass, directly including circularization. found that in about 30% runs are formed, which is much higher than suggested previous studies. mechanism outer responsible for planets. During three-planet crossing, excitation repeated eccentricity often increased secularly...
The ubiquity of planets and diversity planetary systems reveal planet formation encompass many complex competing processes. In this series papers, we develop upgrade a population synthesis model as tool to identify the dominant physical effects calibrate range conditions. Recent searches leads discovery multiple-planet systems. Any theoretical models their origins must take into account dynamical interaction between emerging protoplanets. Here, introduce prescription approximate close...
We investigated the formation of close-in planets (hot Jupiters) by a combination mutual scattering, Kozai effect, and tidal circularization, through N-body simulations three gas giant planets, compared results with discovered planets. found that in about 350 cases out 1200 runs (∼30%), eccentricity one is excited highly enough for circularization close scatterings followed secular effects due to outer such as mechanism, planet becomes damping semimajor axis. The probability scattering not...
The orbital distributions of currently observed extrasolar giant planets allow marginally stable orbits for hypothetical, terrestrial planets. In this paper, we propose that many these systems may not have additional on "stable" orbits, since past dynamical instability among could removed them. We numerically investigate the effects early evolution multiple stability inner, sub-Neptune-like which are modeled as test particles, and determine their dynamically unstable region. Previous studies...
The KOI-94 system is a closely packed, multi-transiting planetary discovered by the Kepler space telescope. It known as first that exhibited rare event called "planet–planet eclipse (PPE)," in which two planets partially overlap with each other their double-transit phase. In this paper, we constrain parameters of an analysis transit timing variations (TTVs). Such constraints are independent radial velocity (RV) recently performed Weiss and coworkers, valuable examining reliability parameter...
We analyze the orbital evolution of terrestrial planetary embryos after oligarchic growth, including effect sweeping Jupiter secular resonance combined with tidal drag during depletion protoplanetary gas disk. Previous studies show that orbits isolated become unstable through long-term gravitational interaction. However, systems formed as a result giant impacts are generally very eccentric, unlike our solar system. Although mechanisms damp eccentricity have been proposed, such not only...
The pumping-up of inclinations and eccentricities caused by sweeping secular resonances in the asteroid belt is studied through numerical orbital integration linear analysis. present asteroids have large mean that cannot be explained planetary perturbations alone. Sweeping associated with depletion primitive solar nebula has been proposed for origin asteroids' orbits (e.g., Ward, Colombo, Franklin 1976). We performed three-dimensional integrations under gravitational forces Jupiter, Saturn,...
We revisit the "dynamical shakeup" model of Solar System terrestrial planet formation, wherein whole process is driven by sweeping Jupiter's secular resonance as gas disk removed. Using a large number 0.5 Gyr-long N-body simulations, we investigate different outcomes produced such scenario. confirm that in contrast to existing models, combined with tidal damping can reproduce low eccentricities and inclinations, high radial mass concentration, planets. At same time, this also drives final...
We report the detection of a double planetary system orbiting around evolved intermediate-mass star HD 4732 from precise Doppler measurements at Okayama Astrophysical Observatory and Australian Astronomical Observatory. The is K0 subgiant with mass 1.7 M☉ solar metallicity. composed two giant planets minimum msin i = 2.4 MJ, orbital period 360.2 days 2732 days, eccentricity 0.13 0.23, respectively. Based on dynamical stability analysis for system, we set upper limit to be about 28 MJ (i >...
The formation of gas giant planets is assumed to be preceded by the emergence solid cores in conventional sequential accretion paradigm. This hypothesis implies that presence Earth-like can inferred from detection giants. A similar prediction cannot made with gravitational instability model, which assumes giants formed collapse fragments analogous their host stars. We propose an observational test for determination dominant planetary channel. Based on we identify several potential avenues...
We report that HAT-P-7 has a common proper motion stellar companion. The companion is located at $ \sim$ 3$ .\!\!\!''$ 9 to the east and estimated be an M5.5V dwarf based on its colors. also confirm presence of third companion, which was first reported by Winn et al. (2009, ApJ, 703, L99), long-term radial velocity measurements. revisit migration mechanism HAT-P-7b given those companions, propose sequential Kozai as likely scenario in this system. This may explain reason for outlier...
We investigate the origin of high orbital eccentricity and inclination present asteroids. The relative velocity between asteroids corresponding to observed is ∼5 km/sec, which much larger than their surface escape velocity. Thus collisions result in disruption rather accretion. It important clarify when how were pumped up, order know environment asteroidal disruption. especially that have not been well understood yet. propose sweeping secular resonances due gravitational potential change...
We present results of direct imaging observations for HAT-P-7 taken with the Subaru HiCIAO and Calar Alto AstraLux. Since close-in transiting planet HAT-P-7b was reported to have a highly tilted orbit, massive bodies such as giant planets, brown dwarfs, or binary star are expected exist in outer region this system. show that there indeed two candidates distant faint stellar companions around HAT-P-7. discuss possible roles played by on orbital evolution HAT-P-7b. conclude is third body...
Abstract We conducted numerical simulations of the dust heating in accretion shocks induced by interaction between infalling envelope and Keplerian disk surrounding a protostar, order to investigate thermal desorption molecules from dust-grain surfaces. It is thought that surfaces amorphous grains are inhomogeneous; various adsorption sites with different binding energies should therefore exist. assumed energy has Gaussian distribution investigated effect on desorption-efficiency evaluation....
Most super-Earths detected by the radial velocity (RV) method have significantly smaller eccentricities than corresponding to dispersion equal their surface escape ("escape eccentricities"). If orbital instability followed giant impacts among protoplanets that migrated from outer regions is considered, it usually considered of merged bodies become comparable those crossing bodies, which are excited up close scattering. However, eccentricity evolution in situ accretion model has not been...
We present the novel concept of evaporation planetesimals as a result bow shocks associated with orbiting supersonic velocities relative to gas in protoplanetary disk. evaluate rates based on simple model describing planetesimal heating and by shock. find that icy radius ≳100 km evaporate efficiently even outside snow line stage planetary oligarchic growth, where strong are produced gravitational perturbations from protoplanets. The obtained results suggest formation giant planets is...
We have investigated excitations of orbital eccentricities and inclinations Kuiper belt objects (KBOs) caused by the sweeping secular resonances during primitive solar nebula depletion. Since gravitational potential rotates longitudes perihelia ascending nodes, depletion leads to migration resonances. In outer (classical) (the region beyond 42 AU), are respectively distributed up 0.6 (radian) 0.2, their root mean squares about 0.2 0.1. These large values not explained present planetary...
We study the dynamical evolution of short-period planets in multiple planetary system during epoch protostellar disk depletion. Through a detailed case analysis for triple-planet around υ Andromedae, we identify necessary condition survival its planet b. In this study, calculate planets' orbit including effects post-Newtonian potential host star, an evolving disk, and due to flattening star produced by stellar rotation tide from planet. At present-day semimajor axis 0.059 AU, negligible...
Most extrasolar planets are observed to have eccentricities much larger than those in the solar system. Some of these sibling planets, with comparable masses, orbiting around same host stars. In multiple planetary systems, eccentricity is modulated by planets' mutual secular interaction as a consequence angular momentum exchange between them. For mature eigenfrequencies this modulation determined their mass and semimajor axis ratios. However, prior disk depletion, self-gravity nascent disks...
We have investigated i) the formation of gravitationally bounded pairs gas-giant planets (which we call "binary planets") from capturing each other through planet-planet dynamical tide during their close encounters and ii) following long-term orbital evolution due to planet-star {\it quasi-static} tides. For initial in phase i), carried out N-body simulations systems consisting three jupiter-mass taking into account tide. The rate binary is as much 10% that undergo crossing this fraction...
We report the detection of planets around two evolved giant stars from radial velocity measurements at Okayama Astrophysical observatory. 24 Boo (G3IV) has a mass $0.99\,M_{\odot}$, radius $10.64\,R_{\odot}$, and metallicity ${\rm [Fe/H]}=-0.77$. The star hosts one planet with minimum $0.91\,M_{\rm Jup}$ an orbital period $30.35{\rm d}$. shortest periods among those ever found by radial-veloocity methods. stellar velocities show additional periodicity $150{\rm d}$, which are probably...
We discuss the detectability of gravitationally bounded pairs gas-giant planets (which we call "binary planets") in extrasolar planetary systems that are formed through orbital instability followed by planet-planet dynamical tides during their close encounters, based on results N-body simulations Ochiai, Nagasawa and Ida (Paper I). Paper I showed formation probability a binary is as much $\sim 10\%$ for three giant planet undergo instability, after post-capture long-term tidal evolution,...