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Dynamics and Formation of the Near-resonant K2-24 System: Insights from Transit-timing Variations and Radial Velocities
- Source :
- BASE-Bielefeld Academic Search Engine
- Publication Year :
- 2018
- Publisher :
- American Astronomical Society, 2018.
-
Abstract
- While planets between the size of Uranus and Saturn are absent within the Solar System, the star K2-24 hosts two such planets, K2-24b and c, with radii equal to $5.4~R_E$ and $7.5~R_E$, respectively. The two planets have orbital periods of 20.9 days and 42.4 days, residing only 1% outside the nominal 2:1 mean-motion resonance. In this work, we present results from a coordinated observing campaign to measure planet masses and eccentricities that combines radial velocity (RV) measurements from Keck/HIRES and transit-timing measurements from K2 and Spitzer. K2-24b and c have low, but non-zero, eccentricities of $e_1 \sim e_2 \sim 0.08$. The low observed eccentricities provide clues regarding the formation and dynamical evolution of K2-24b and K2-24c, suggesting that they could be the result of stochastic gravitational interactions with a turbulent protoplanetary disk, among other mechanisms. K2-24b and c are $19\pm2~M_E$ and $15\pm2~M_E$, respectively; K2-24c is 20% less massive than K2-24b, despite being 40% larger. Their large sizes and low masses imply large envelope fractions, which we estimate at $26^{+3}_{-3}\%$ and $52^{+5}_{-3}\%$. In particular, K2-24c's large envelope presents an intriguing challenge to the standard model of core nucleated accretion that predicts the onset of runaway accretion when $f_{env} \approx 50\%$.<br />14 pages, 9 figures, 2 tables, accepted to AJ
- Subjects :
- Earth and Planetary Astrophysics (astro-ph.EP)
Physics
Solar System
Uranus
FOS: Physical sciences
Astronomy and Astrophysics
Astrophysics
Protoplanetary disk
01 natural sciences
Accretion (astrophysics)
010309 optics
Radial velocity
Space and Planetary Science
Planet
Saturn
0103 physical sciences
Transit (astronomy)
010303 astronomy & astrophysics
Astrophysics - Earth and Planetary Astrophysics
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Journal :
- BASE-Bielefeld Academic Search Engine
- Accession number :
- edsair.doi.dedup.....a3d29debf482e0a7d274a321d9bd81a6