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.

methods: observational

planets and satellites: detection

techniques: high angular resolution

techniques: radial velocities

techniques: spectroscopic

techniques: photometric

Författare

Teruyuki Hirano

Unknown organization

Fei Dai

Unknown organization

D. Gandolfi

Unknown organization

Akihiko Fukui

Unknown organization

John H. Livingston

Unknown organization

Kohei Miyakawa

Unknown organization

Michael Endl

Unknown organization

William D. Cochran

Unknown organization

Francisco J. Alonso-Floriano

Unknown organization

M. Kuzuhara

Unknown organization

David Montes

Unknown organization

Tsuguru Ryu

Unknown organization

Simon Albrecht

Unknown organization

Oscar Barragan

Unknown organization

Juan Cabrera

Unknown organization

Szilard Csizmadia

Unknown organization

Hans Deeg

Unknown organization

Philipp Eigmüller

Unknown organization

Anders Erikson

Unknown organization

Malcolm Fridlund

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

Sascha Grziwa

Unknown organization

Eike W. Guenther

Unknown organization

Artie P. Hatzes

Unknown organization

Judith Korth

Unknown organization

T. Kudo

Unknown organization

Nobuhiko Kusakabe

Unknown organization

Norio Narita

Unknown organization

David Nespral

Unknown organization

Grzegorz Nowak

Unknown organization

Martin Pätzold

Unknown organization

Enric Palle

Unknown organization

Carina Persson

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

Jorge Prieto-Arranz

Unknown organization

Heike Rauer

Unknown organization

I. Ribas

Unknown organization

B. Sato

Unknown organization

Alexis M. S. Smith

Unknown organization

M. Tamura

Unknown organization

Yusuke Tanaka

Unknown organization

Vincent Van Eylen

Unknown organization

Joshua N. Winn

Unknown organization

Astronomical Journal

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

Vol. 155 3 127-

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.3847/1538-3881/aaa9c1