Mass determination of the 1:3:5 near-resonant planets transiting GJ 9827 (K2-135)
Artikel i vetenskaplig tidskrift, 2018

Context. Multiplanet systems are excellent laboratories to test planet formation models as all planets are formed under the same initial conditions. In this context, systems transiting bright stars can play a key role, since planetary masses, radii, and bulk densities can be measured. Aims. GJ 9827 (K2-135) has recently been found to host a tightly packed system consisting of three transiting small planets whose orbital periods of 1.2, 3.6, and 6.2 days are near the 1:3:5 ratio. GJ 9827 hosts the nearest planetary system (~30 pc) detected by NASA's Kepler or K2 space mission. Its brightness (V = 10.35 mag) makes the star an ideal target for detailed studies of the properties of its planets. Methods. Combining the K2 photometry with high-precision radial-velocity measurements gathered with the FIES, HARPS, and HARPS-N spectrographs we revised the system parameters and derive the masses of the three planets. Results. We find that GJ 9827 b has a mass of Mb = 3.69-0.46+0.48 M and a radius of Rb = 1.58-0.13+0.14 R, yielding a mean density of ρb = 5.11-1.27+1.74 g cm-3. GJ 9827 c has a mass of Mc = 1.45-0.57+0.58 M, radius of Rc = 1.24-0.11+0.11 R, and a mean density of ρc = 4.13-1.77+2.31 g cm-3. For GJ 9827 d, we derive Md = 1.45-0.57+0.58 M, Rd = 1.24-0.11+0.11 R, and ρd = 1.51-0.53+0.71 g cm-3. Conclusions. GJ 9827 is one of the few known transiting planetary systems for which the masses of all planets have been determined with a precision better than 30%. This system is particularly interesting because all three planets are close to the limit between super-Earths and sub-Neptunes. The planetary bulk compositions are compatible with a scenario where all three planets formed with similar core and atmosphere compositions, and we speculate that while GJ 9827 b and GJ 9827 c lost their atmospheric envelopes, GJ 9827 d maintained its primordial atmosphere, owing to the much lower stellarirradiation. This makes GJ 9827 one of the very few systems where the dynamical evolution and the atmosphericescape can be studied in detail for all planets, helping us to understand how compact systems form and evolve.

Stars: individual: GJ 9827

Techniques: high angular resolution

Stars: abundances

Techniques: radial velocities

Planetary systems

Techniques: photometric

Författare

J. Prieto-Arranz

Instituto Astrofisico de Canarias

Universidad de la Laguna

E. Palle

Instituto Astrofisico de Canarias

Universidad de la Laguna

D. Gandolfi

Universita degli Studi di Torino

O. Barragán

Universita degli Studi di Torino

E. W. Guenther

Instituto Astrofisico de Canarias

Thüringer Landessternwarte Tautenburg

Fei Dai

Massachusetts Institute of Technology (MIT)

Princeton University

Malcolm Fridlund

Universiteit Leiden

Chalmers, Rymd-, geo- och miljövetenskap, Onsala rymdobservatorium

T. Hirano

Tokyo Institute of Technology

J. Livingston

University of Tokyo

R. Luque

Instituto Astrofisico de Canarias

Universidad de la Laguna

Prajwal Niraula

Wesleyan University Middletown

Carina Persson

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

S. Redfield

Wesleyan University Middletown

Simon Albrecht

Aarhus Universitet

R. Alonso

Instituto Astrofisico de Canarias

Universidad de la Laguna

Giuliano Antoniciello

Universita degli Studi di Torino

J. Cabrera

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

William D. Cochran

The University of Texas at Austin

Szilard Csizmadia

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

H. Deeg

Instituto Astrofisico de Canarias

Universidad de la Laguna

P. Eigmüller

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

M. Endl

The University of Texas at Austin

Anders Erikson

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

M.E. Everett

National Optical Astronomy Observatory

A. Fukui

National Institutes of Natural Sciences - National Astronomical Observatory of Japan

S. Grziwa

Universität zu Köln

A. Hatzes

Thüringer Landessternwarte Tautenburg

D. Hidalgo

Instituto Astrofisico de Canarias

Universidad de la Laguna

M. Hjorth

Aarhus Universitet

Judith Korth

Universität zu Köln

D. Lorenzo-Oliveira

Universidade Cidade de Sao Paulo

F. Murgas

Aarhus Universitet

Norio Narita

University of Tokyo

National Institutes of Natural Sciences

David Nespral

Instituto Astrofisico de Canarias

Universidad de la Laguna

G. Nowak

Universidad de la Laguna

Instituto Astrofisico de Canarias

Martin Pätzold

Universität zu Köln

P. Montañez Rodríguez

Universidad de la Laguna

Instituto Astrofisico de Canarias

H. Rauer

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

Technische Universität Berlin

I. Ribas

CSIC - Instituto de Ciencias del Espacio (ICE)

Institut d'Estudis Espacials de Catalunya (IEEC)

Alexis M. S. Smith

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

T. Trifonov

Max Planck-institutet

Vincent Van Eylen

Universiteit Leiden

J. N. Winn

Princeton University

Astronomy and Astrophysics

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

Vol. 618 32872

Exoplaneter från rymden - CHEOPS och PLATO

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

Ämneskategorier

Astronomi, astrofysik och kosmologi

Fundament

Grundläggande vetenskaper

DOI

10.1051/0004-6361/201832872

Mer information

Senast uppdaterat

2019-01-18