253 citations · 3k across the 95 of their papers we have counts for
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Orbital Stability of Apsidally Aligned Planetary Systems
Gabriel Teixeira Guimarães, Eiichiro Kokubo
The dynamical stability of compact planetary systems is known to depend strongly on orbital eccentricities, but the physical role of apsidal alignment remains poorly understood. We…
Planet-Planet Scattering Explains the Mass-Eccentricity Relation of Warm Jupiters
Jiayin Dong, Eve J. Lee, Eiichiro Kokubo +2
Warm giant planets with orbital periods of tens of days exhibit a positive correlation between mass and eccentricity. We interpret this trend as the outcome of planet-planet scatte…
A Scaling Law for the Orbital Architecture of Planetary Systems Formed by Gravitational Scattering and Collisions
Eiichiro Kokubo, Haruka Hoshino, Yuji Matsumoto +1
In the standard formation models of terrestrial planets in the solar system and close-in super-Earths in non-resonant orbits recently discovered by exoplanet observations, planets…
Semi-analytical model for the dynamical evolution of planetary system II: Application to systems formed by a planet formation model
Tadahiro Kimura, Eiichiro Kokubo, Yuji Matsumoto +2
The standard formation model of close-in low-mass planets involves efficient inward migration followed by growth through giant impacts after the protoplanetary gas disk disperses.…
A Resonant Beginning for the Solar System Terrestrial Planets
Shuo Huang, Chris Ormel, Simon Portegies Zwart +2
In the past two decades, transit surveys have revealed a class of planets with thick atmospheres -- sub-Neptunes -- that must have completed their accretion in protoplanet disks. W…
Semi-analytical model for the dynamical evolution of planetary systems via giant impacts
Tadahiro Kimura, Haruka Hoshino, Eiichiro Kokubo +2
In the standard model of terrestrial planet formation, planets are formed through giant impacts of planetary embryos after the dispersal of the protoplanetary gas disc. Traditional…
Stellar Obliquity of the Ultra-Short-Period Planet System HD 93963
Huan-Yu Teng, Fei Dai, Andrew W. Howard +24
We report an observation of the Rossiter-McLaughlin (RM) effect of the transiting planet HD 93963 Ac, a mini-Neptune planet orbiting a G0-type star with an orbital period of $P_{\r…
Global N-body Simulation of Gap Edge Structures Created by Perturbations from a Small Satellite Embedded in Saturn's Rings II: The Effect of Satellite's Orbital Eccentricity and Inclination
Naoya Torii, Shigeru Ida, Eiichiro Kokubo +1
Pan and Daphnis are embedded in Saturn's rings and opening a gap with satellite wakes at the gap edges. Furthermore, in the case of Daphnis, pronounced vertical wall structures cas…
Oligarchic growth of protoplanets in planetesimal rings
Yuki Kambara, Eiichiro Kokubo
In the standard planet formation scenario, planetesimals are assumed to form throughout the protoplanetary disk and to be smoothly distributed in the radial direction except for th…
Gliese 12 b: A temperate Earth-sized planet at 12 pc ideal for atmospheric transmission spectroscopy
M. Kuzuhara, A. Fukui, J. H. Livingston +103
Recent discoveries of Earth-sized planets transiting nearby M dwarfs have made it possible to characterize the atmospheres of terrestrial planets via follow-up spectroscopic observ…
Global N-body Simulation of Gap Edge Structures Created by Perturbations from a Small Satellite Embedded in Saturn's Rings
Naoya Torii, Shigeru Ida, Eiichiro Kokubo +1
Observations by the Voyager and Cassini spacecrafts have revealed various striking features of the gap structure in Saturn's ring, such as the density waves, sharp edge, and vertic…
Two long-period giant planets around two giant stars: HD 112570 and HD 154391
Guang-Yao Xiao, Huan-Yu Teng, Jianzhao Zhou +24
We present the discoveries of two giant planets orbiting the red giant branch (RGB) star HD 112570 and the red clump (RC) star HD 154391, based on the radial velocity (RV) measurem…
Formation of inner planets in the presence of a Cold Jupiter: orbital evolution and relative velocities of planetesimals
Kangrou Guo, Eiichiro Kokubo
We investigate the orbital evolution of planetesimals in the inner disk in the presence of nebula gas and a (proto-) cold Jupiter. By varying the mass, eccentricity, and semi-major…
Revisiting Planetary Systems in Okayama Planet Search Program: A new long-period planet, RV astrometry joint analysis, and multiplicity-metallicity trend around evolved stars
Huan-Yu Teng, Bun'ei Sato, Masayuki Kuzuhara +15
In this study, we revisit 32 planetary systems around evolved stars observed within the framework of the Okayama Planet Search Program and its collaborative framework of the EAPS-N…
Size Dependence of the Bouncing Barrier in Protoplanetary Dust Growth
Sota Arakawa, Satoshi Okuzumi, Misako Tatsuuma +5
Understanding the collisional behavior of dust aggregates is essential in the context of planet formation. It is known that low-velocity collisions of dust aggregates result in bou…
An Earth-sized Planet around an M5 Dwarf Star at 22 pc
Teruyuki Hirano, Fei Dai, John H. Livingston +46
We report on the discovery of an Earth-sized transiting planet () in a day orbit around K2-415 (EPIC 211414619), an M5V star at 22 pc. The pla…
Threshold velocity for collisional growth of porous dust aggregates consisting of cohesive frictionless spheres
Sota Arakawa, Hidekazu Tanaka, Eiichiro Kokubo +2
Understanding the collisional outcomes of dust aggregates and dependence on material properties of the constituting particles is of great importance toward understanding planet for…
Orbital structure of planetary systems formed by giant impacts: stellar mass dependence
Haruka Hoshino, Eiichiro Kokubo
Recent exoplanet surveys revealed that for solar-type stars, close-in Super-Earths are ubiquitous and many of them are in multi-planet systems. These systems are more compact than…
A Close-in Planet Orbiting Giant Star HD 167768
Huan-Yu Teng, Bun'ei Sato, Masanobu Kunitomo +12
We report the detection of a giant planet orbiting a G-type giant star HD 167768 from radial velocity measurements using HIgh Dispersion Echelle Spectrograph (HIDES) at Okayama Ast…
Planetesimal formation by the gravitational instability of dust ring structures
Sanemichi Z. Takahashi, Eiichiro Kokubo, Shu-ichiro Inutsuka
We investigate the gravitational instability (GI) of dust-ring structures and the formation of planetesimals by their gravitational collapse. The normalized dispersion relation of…
Collisional growth efficiency of dust aggregates and its independence of the strength of interparticle rolling friction
Sota Arakawa, Hidekazu Tanaka, Eiichiro Kokubo
The pairwise collisional growth of dust aggregates consisting submicron-sized grains is the first step of the planet formation, and understanding the collisional behavior of dust a…
A Trio of Giant Planets Orbiting Evolved Star HD 184010
Huan-Yu Teng, Bun'ei Sato, Takuya Takarada +11
We report the discovery of a triple-giant-planet system around an evolved star HD 184010 (HR 7421, HIP 96016). This discovery is based on observations from Okayama Planet Search Pr…
Planetesimal Dynamics in the Presence of a Giant Planet II: Dependence on Planet Mass and Eccentricity
Kangrou Guo, Eiichiro Kokubo
The presence of an early-formed giant planet in the protoplanetary disk has mixed influence on the growth of other planetary embryos. Gravitational perturbation from the planet can…
Impacts of viscous dissipation on collisional growth and fragmentation of dust aggregates
Sota Arakawa, Hidekazu Tanaka, Eiichiro Kokubo
Understanding the collisional behavior of dust aggregates consisting of submicron-sized grains is essential to unveiling how planetesimals formed in protoplanetary disks. It is kno…