期刊
ASTROPHYSICAL JOURNAL
卷 818, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.3847/0004-637X/818/1/46
关键词
planetary systems; stars: fundamental parameters; stars: individual (K2-25) stars; late-type; stars: low-mass; stars: statistics
资金
- Space Telescope Science Institute [51364]
- NASA [NAS 5-26555, NNX11AC33G]
- Swiss National Science Foundation
- US National Science Foundation [ASTR1229522]
- University of Texas at Austin
- Korean GMT Project of KASI
- NASA Office of Space Science [NNX09AF08G]
- Robert Martin Ayers Sciences Fund
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [1229522] Funding Source: National Science Foundation
Studying the properties of young planetary systems can shed light on how the dynamics and structure of planets evolve during their most formative years. Recent K2 observations of nearby young clusters (10-800 Myr) have. facilitated the discovery of such planetary systems. Here we report the discovery of a Neptune-sized planet transiting an M4.5 dwarf (K2-25) in the Hyades cluster (650-800 Myr). The light. curve shows a strong periodic signal at 1.88 days, which we attribute to spot coverage and rotation. We confirm that. the planet host is a member of the Hyades by measuring the radial velocity of the system with the high-resolution near-infrared spectrograph Immersion Grating Infrared Spectrometer. This enables us to calculate a distance based on K2-25's kinematics and membership to the Hyades, which in turn provides a stellar radius and mass to; 5%-10%, better than what is currently possible for most Kepler M dwarfs (12%-20%). We use the derived stellar density as a prior on fitting the K2 transit photometry, which provides weak constraints on eccentricity. Utilizing a combination of adaptive optics imaging and high-resolution spectra, we rule out the possibility that the signal is due to a bound or background eclipsing binary, confirming the transits' planetary origin. K2-25b has a radius (3.43 (+0.95)(-0.31)- R-circle plus) much larger than older Kepler planets with similar orbital periods (3.485 days) and host-star masses (0.29 M-circle dot). This suggests that close-in planets lose some of their atmospheres past the first few hundred million years. Additional transiting planets around the Hyades, Pleiades, and Praesepe clusters from K2 will help confirm whether this planet is atypical or representative of other close-in planets of similar age.
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