Exoplanets around Low-mass Stars Unveiled by K2
Artikel i vetenskaplig tidskrift, 2018

We present the detection and follow-up observations of planetary candidates around low-mass stars observed by the K2 mission. Based on light-curve analysis, adaptive-optics imaging, and optical spectroscopy at low and high resolution (including radial velocity measurements), we validate 16 planets around 12 low-mass stars observed during K2 campaigns 5–10. Among the 16 planets, 12 are newly validated, with orbital periods ranging from 0.96 to 33 days. For one of the planets (K2-151b), we present ground-based transit photometry, allowing us to refine the ephemerides. Combining our K2 M-dwarf planets together with the validated or confirmed planets found previously, we investigate the dependence of planet radius R p on stellar insolation and metallicity [Fe/H]. We confirm that for periods P ≲ 2 days, planets with a radius Rp≳ 2 R⊕ are less common than planets with a radius between 1–2 R⊕. We also see a hint of the “radius valley” between 1.5 and 2 R⊕, which has been seen for close-in planets around FGK stars. These features in the radius/period distribution could be attributed to photoevaporation of planetary envelopes by high-energy photons from the host star, as they have for FGK stars. For the M dwarfs, though, the features are not as well defined, and we cannot rule out other explanations such as atmospheric loss from internal planetary heat sources or truncation of the protoplanetary disk. There also appears to be a relation between planet size and metallicity: the few planets larger than about 3 R⊕ are found around the most metal-rich M dwarfs.

techniques: spectroscopic

methods: observational

techniques: high angular resolution

planets and satellites: detection

techniques: radial velocities

techniques: photometric

Författare

Teruyuki Hirano

Organisation okänd

Fei Dai

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D. Gandolfi

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Akihiko Fukui

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John H. Livingston

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Kohei Miyakawa

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Michael Endl

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William D. Cochran

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Francisco J. Alonso-Floriano

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M. Kuzuhara

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David Montes

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Tsuguru Ryu

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Simon Albrecht

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Oscar Barragan

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Juan Cabrera

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Szilard Csizmadia

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Hans Deeg

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Philipp Eigmüller

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Anders Erikson

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Malcolm Fridlund

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik

Sascha Grziwa

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Eike W. Guenther

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Artie P. Hatzes

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Judith Korth

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T. Kudo

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Nobuhiko Kusakabe

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Norio Narita

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David Nespral

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Grzegorz Nowak

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Martin Pätzold

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Enric Palle

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Carina Persson

Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik, Galaktisk astrofysik

Jorge Prieto-Arranz

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Heike Rauer

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I. Ribas

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B. Sato

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Alexis M. S. Smith

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M. Tamura

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Yusuke Tanaka

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Vincent Van Eylen

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Joshua N. Winn

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Astronomical Journal

0004-6256 (ISSN) 1538-3881 (eISSN)

Vol. 155 3 127-

Exoplaneter från rymden - CHEOPS och PLATO

Rymdstyrelsen, 2017-01-01 -- 2022-12-31.

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.3847/1538-3881/aaa9c1

Mer information

Senast uppdaterat

2018-10-12