Detection and Doppler monitoring of K2-285 (EPIC 246471491), a system of four transiting planets smaller than Neptune
Artikel i vetenskaplig tidskrift, 2019

Context. The Kepler extended mission, also known as K2, has provided the community with a wealth of planetary candidates that orbit stars typically much brighter than the targets of the original mission. These planet candidates are suitable for further spectroscopic follow-up and precise mass determinations, leading ultimately to the construction of empirical mass-radius diagrams. Particularly interesting is to constrain the properties of planets that are between Earth and Neptune in size, the most abundant type of planet orbiting Sun-like stars with periods of less than a few years. Aims. Among many other K2 candidates, we discovered a multi-planetary system around EPIC 246471491, referred to henceforth as K2-285, which contains four planets, ranging in size from twice the size of Earth to nearly the size of Neptune. We aim here at confirming their planetary nature and characterizing the properties of this system. Methods. We measure the mass of the planets of the K2-285 system by means of precise radial-velocity measurements using the CARMENES spectrograph and the HARPS-N spectrograph. Results. With our data we are able to determine the mass of the two inner planets of the system with a precision better than 15%, and place upper limits on the masses of the two outer planets. Conclusions. We find that K2-285b has a mass of M b = 9.68 -1.37+1.21 M · and a radius of R b = 2.59 -0.06+0.06 R · , yielding a mean density of ρ b = 3.07 -0.45+0.45 g cm -3 , while K2-285c has a mass of M c = 15.68 -2.13+2.28 M · , radius of R c = 3.53 -0.08+0.08 R · , and a mean density of ρ c = 1.95 -0.28+0.32 g cm -3 . For K2-285d (R d = 2.48 -0.06+0.06 R · ) and K2-285e (R e = 1.95 -0.05+0.05 R · ), the upper limits for the masses are 6.5 M · and 10.7 M · , respectively. The system is thus composed of an (almost) Neptune-twin planet (in mass and radius), two sub-Neptunes with very different densities and presumably bulk composition, and a fourth planet in the outermost orbit that resides right in the middle of the super-Earth/sub-Neptune radius gap. Future comparative planetology studies of this system would provide useful insights into planetary formation, and also a good test of atmospheric escape and evolution theories.

Planets and satellites: atmospheres

Planets and satellites: fundamental parameters

Planets and satellites: detection

Planets and satellites: dynamical evolution and stability

Planetary systems

Författare

Enric Palle

Universidad de la Laguna

Instituto Astrofisico de Canarias

G. Nowak

Universidad de la Laguna

Instituto Astrofisico de Canarias

R. Luque

Universidad de la Laguna

Instituto Astrofisico de Canarias

D. Hidalgo

Universidad de la Laguna

Instituto Astrofisico de Canarias

O. Barragán

Universita degli Studi di Torino

J. Prieto-Arranz

Universidad de la Laguna

Instituto Astrofisico de Canarias

T. Hirano

Tokyo Institute of Technology

C.W.M. Fridlund

Universiteit Leiden

D. Gandolfi

Universita degli Studi di Torino

J. Livingston

University of Tokyo

Fei Dai

Princeton University

Massachusetts Institute of Technology (MIT)

Juan Carlos Morales

Institut d'Estudis Espacials de Catalunya (IEEC)

Universitat Autonoma de Barcelona (UAB)

Marina Lafarga

Universitat Autonoma de Barcelona (UAB)

Institut d'Estudis Espacials de Catalunya (IEEC)

Simon Albrecht

Aarhus Universitet

R. Alonso

Universidad de la Laguna

Instituto Astrofisico de Canarias

P. J. Amado

CSIC - Instituto de Astrofísica de Andalucía (IAA)

J. A. Caballero

Centro de Astrobiologia (CAB)

J. Cabrera

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

William D. Cochran

Freie Universität Berlin

Szilard Csizmadia

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

H. Deeg

Instituto Astrofisico de Canarias

Universidad de la Laguna

P. Eigmüller

Technische Universität Berlin

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

M. Endl

The University of Texas at Austin

Anders Erikson

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

A. Fukui

Instituto Astrofisico de Canarias

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

E. W. Guenther

Thüringer Landessternwarte Tautenburg

S. Grziwa

Universität zu Köln

A. Hatzes

Thüringer Landessternwarte Tautenburg

Judith Korth

Universität zu Köln

M. Kürster

Max Planck-institutet

M. Kuzuhara

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

National Institutes of Natural Sciences

P. M. Rodriguez

Universidad de la Laguna

Instituto Astrofisico de Canarias

F. Murgas

Instituto Astrofisico de Canarias

Universidad de la Laguna

Norio Narita

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

Instituto Astrofisico de Canarias

David Nespral

Instituto Astrofisico de Canarias

Universidad de la Laguna

Martin Pätzold

Universität zu Köln

Carina Persson

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

A. Quirrenbach

Landessternwarte Heidelberg

H. Rauer

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

Freie Universität Berlin

Technische Universität Berlin

S. Redfield

Wesleyan University

A. Reiners

Georg-August-Universität Göttingen

I. Ribas

Institut d'Estudis Espacials de Catalunya (IEEC)

Universitat Autonoma de Barcelona (UAB)

Alexis M. S. Smith

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

Vincent Van Eylen

Universiteit Leiden

J. N. Winn

Princeton University

M. Zechmeister

Georg-August-Universität Göttingen

Astronomy and Astrophysics

0004-6361 (ISSN) 1432-0746 (eISSN)

Vol. 623 A41

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.1051/0004-6361/201834001

Mer information

Senast uppdaterat

2019-05-26