T. Hirano

K2-106, a system containing a metal-rich planet and a planet of lower density

Planets in the mass range from 2 to 15 M_Earth are very diverse. Some of them have low densities, while others are very dense. By measuring the masses and radii, the mean densities, structure, and composition of the planets are constrained. These parameters also give us important information about their formation and evolution, and about possible processes for atmospheric loss.We determined the masses, radii, and mean densities for the two transiting planets orbiting K2-106. The inner planet has an ultra-short period of 0.57 days. The period of the outer planet is 13.3 days. Although the two planets have similar masses, their densities are very different. For K2-106b we derive Mb=8.36-0.94+0.96 M_Earh, Rb=1.52+/-0.16 R_Earth, and a high density of 13.1-3.6+5.4 g/cm^3. For K2-106c, we find Mc=5.8-3.0+3.3 M_Earth, Rc=2.50-0.26+0.27 R_Earth and a relatively low density of 2.0-1.1+1.6 g/cm^3.Since the system contains two planets of almost the same mass, but different distances from the host star, it is an excellent laboratory to study atmospheric escape. In agreement with the theory of atmospheric-loss processes, it is likely that the outer planet has a hydrogen-dominated atmosphere. The mass and radius of the inner planet is in agreement with theoretical models predicting an iron core containing 80+20-30% of its mass. Such a high metal content is surprising, particularly given that the star has an ordinary (solar) metal abundance. We discuss various possible formation scenarios for this unusual planet.

Spin-Orbit Alignment of Exoplanet Systems: Ensemble Analysis Using Asteroseismology

The angle

The K2-ESPRINT Project II: Spectroscopic follow-up of three exoplanet systems from Campaign 1 of K2

\psi

THE K2-ESPRINT PROJECT. V. A SHORT-PERIOD GIANT PLANET ORBITING A SUBGIANT STAR

between a planets orbital axis and the spin axis of its parent star is an important diagnostic of planet formation, migration, and tidal evolution. We seek empirical constraints on

K2-99: a subgiant hosting a transiting warm Jupiter in an eccentric orbit and a long-period companion

\psi

K2-137 b: an Earth-sized planet in a 4.3-h orbit around an M-dwarf

by measuring the stellar inclination

K2-141 b. A 5-M_oplus super-Earth transiting a K7 V star every 6.7 hours

i_{\rm s}

Orbital Characterization of GJ1108A System, and Comparison of Dynamical Mass with Model-derived Mass for Resolved Binaries

via asteroseismology for an ensemble of 25 solar-type hosts observed with NASAs Kepler satellite. Our results for

Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)

i_{\rm s}

Super-Earth of 8 M⊕ in a 2.2-day orbit around the K5V star K2-216

are consistent with alignment at the 2-