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DISCOVERY AND VALIDATION OF A HIGH-DENSITY SUB-NEPTUNE FROM THE K2 MISSION

We report the discovery of K2-56b, a high-density sub-Neptune exoplanet, made using photometry from Campaign 4 of the two-wheeled Kepler (K2) mission, ground-based radial velocity (RV) follow-up from HARPS and high-resolution lucky and adaptive optics imaging obtained using AstraLux and MagAO, respectively. The host star is a bright (V - 11.04, K-s - 9.37), slightly metal-poor ([Fe/H] - -0.15 +/- 0.05 dex) solar analogue located at 152.1(-7.4)(+9.7) pc from Earth, for which we find a radius of R-* = 0.928(-04040)(+0.055) and a mass of M-* = 0.961(-0.029)(+0.032) M-circle dot. A joint analysis of the K2 photometry and HARPS RVs reveal that the planet is in a approximate to 42 day orbit around its host star, has a radius of 2.23(011)(+0.14)R(circle plus), and a mass of 16.3(6.1)(+6.0) M-circle plus. Although the data at hand put the planet in the region of the massradius diagram where we could expect planets with a pure rock (i.e., magnesium silicate) composition using two-layer models (i.e., between rock/iron and rock/ice compositions), we discuss more realistic three-layer composition models which can explain the high density of the discovered exoplanet. The fact that the planet lies in the boundary between "possibly rocky" and "non-rocky" exoplanets makes it an interesting planet for future RV follow-up.

Identiferoai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/624071
Date10 October 2016
CreatorsEspinoza, Nestor, Brahm, Rafael, Jordan, Andres, Jenkins, James S., Rojas, Felipe, Jofre, Paula, Madler, Thomas, Rabus, Markus, Chaname, Julio, Pantoja, Blake, Soto, Maritza G., Morzinski, Katie M., Males, Jared R., Ward-Duong, Kimberly, Close, Laird M.
ContributorsUniv Arizona, Steward Observ
PublisherIOP PUBLISHING LTD
Source SetsUniversity of Arizona
LanguageEnglish
Detected LanguageEnglish
TypeArticle
Rights© 2016. The American Astronomical Society. All rights reserved.
Relationhttp://stacks.iop.org/0004-637X/830/i=1/a=43?key=crossref.2397df04f9f37c10f54db77ec5ee83f5

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