Discovery of two warm mini-Neptunes with contrasting densities orbiting the young K3V star TOI-815
Artikel i vetenskaplig tidskrift, 2024

We present the discovery and characterization of two warm mini-Neptunes transiting the K3V star TOI-815 in a K–M binary system. Analysis of its spectra and rotation period reveal the star to be young, with an age of 200+−400200 Myr. TOI-815b has a 11.2-day period and a radius of 2.94 ± 0.05 R+ with transits observed by TESS, CHEOPS, ASTEP, and LCOGT. The outer planet, TOI-815c, has a radius of 2.62 ± 0.10 R+, based on observations of three nonconsecutive transits with TESS; targeted CHEOPS photometry and radial velocity follow-up with ESPRESSO were required to confirm the 35-day period. ESPRESSO confirmed the planetary nature of both planets and measured masses of 7.6 ± 1.5 M+ (ρP = 1.64+−003331 g cm−3) and 23.5 ± 2.4 M+ (ρP = 7.2+−1110 g cm−3), respectively. Thus, the planets have very different masses, which is unusual for compact multi-planet systems. Moreover, our statistical analysis of mini-Neptunes orbiting FGK stars suggests that weakly irradiated planets tend to have higher bulk densities compared to those undergoing strong irradiation. This could be ascribed to their cooler atmospheres, which are more compressed and denser. Internal structure modeling of TOI-815b suggests it likely has a H-He atmosphere that constitutes a few percent of the total planet mass, or higher if the planet is assumed to have no water. In contrast, the measured mass and radius of TOI-815c can be explained without invoking any atmosphere, challenging planetary formation theories. Finally, we infer from our measurements that the star is viewed close to pole-on, which implies a spin-orbit misalignment at the 3σ level. This emphasizes the peculiarity of the system’s orbital architecture, and probably hints at an eventful dynamical history.

techniques: radial velocities

techniques: photometric

planets and satellites: composition

stars: individual: TOI-815

planets and satellites: detection

planets and satellites: formation

Författare

A. Psaridi

Université de Genève

H. P. Osborn

Universität Bern

F. Bouchy

Université de Genève

M. Lendl

Université de Genève

Léna Parc

Université de Genève

N. Billot

Université de Genève

C. Broeg

Universität Bern

S.G. Sousa

Universidade do Porto

V. Adibekyan

Universidade do Porto

Omar Attia

Université de Genève

A. Bonfanti

Institut fur Weltraumforschung

Hritam Chakraborty

Université de Genève

Karen A. Collins

Harvard-Smithsonian Center for Astrophysics

Jeanne Davoult

Universität Bern

E. Delgado Mena

Universidade do Porto

N. Grieves

Université de Genève

T. Guillot

Observatoire de la Cote d'Azur

A. Heitzmann

Université de Genève

R. Helled

Universität Zürich

Coel Hellier

Keele University

Jon M. Jenkins

NASA Ames Research Center

Henrik Knierim

Universität Zürich

A. Krenn

Institut fur Weltraumforschung

Jack J. Lissauer

NASA Ames Research Center

R. Luque

University of Chicago

D. Rapetti

NASA Ames Research Center

N. C. Santos

Universidade do Porto

Olga Suárez

Observatoire de la Cote d'Azur

J. Venturini

Université de Genève

Francis P. Wilkin

Union College

T.G. Wilson

The University of Warwick

J. N. Winn

Princeton University

C. Ziegler

Stephen F. Austin State University

Tiziano Zingales

Università di Padova

Y. Alibert

Universität Bern

A. Brandeker

Stockholms universitet

J. A. Egger

Universität Bern

D. Gandolfi

Universita degli Studi di Torino

M.J. Hooton

University of Cambridge

A. Tuson

University of Cambridge

S. Ulmer-Moll

Université de Genève

L. Abe

Observatoire de la Cote d'Azur

R. Allart

Université de Montréal

R. Alonso

Instituto de Astrofísica de Canarias

D. Anderson

The University of Warwick

G. A. Escudé

Institut de Ciències de l'Espai (ICE) - CSIC

T. Bárczy

Admatis

D. Barrado

Centro de Astrobiologia (CAB)

S.C.C. Barros

Universidade do Porto

W. Baumjohann

Institut fur Weltraumforschung

M. Beck

Université de Genève

T. Beck

Universität Bern

W. Benz

Universität Bern

X. Bonfils

Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)

L. Borsato

Istituto nazionale di astrofisica (INAF)

V. Bourrier

Université de Genève

D. R. Ciardi

California Institute of Technology (Caltech)

A. Collier Cameron

University of St Andrews

S. Charnoz

Institut de Physique du Globe de Paris

M. Cointepas

Université de Genève

Szilard Csizmadia

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

P. E. Cubillos

Institut fur Weltraumforschung

G. Lo Curto

European Southern Observatory Santiago

M. B. Davies

Lunds universitet

Tansu Daylan

Washington University in St. Louis

M. Deleuil

Laboratoire d'Astrophysique de Marseille

A. Deline

Université de Genève

L. Delrez

Universite de Liège

O. Demangeon

Universidade do Porto

B.O. Demory

Universität Bern

C. Dorn

Eidgenössische Technische Hochschule Zürich (ETH)

X. Dumusque

Université de Genève

D. Ehrenreich

Université de Genève

Anders Erikson

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

A. L. des Etangs

Institut d 'Astrophysique de Paris

D. de Miguel

Airbus Group

A. Fortier

Universität Bern

L. Fossati

Institut fur Weltraumforschung

Yolanda G.C. Frensch

Université de Genève

Malcolm Fridlund

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

Universiteit Leiden

Michaël Gillon

Universite de Liège

M. Gudel

Universität Wien

Maximilian N. Günther

European Space Research and Technology Centre (ESA ESTEC)

J. Hagelberg

Université de Genève

Ch. Helling

Institut fur Weltraumforschung

S. Hoyer

Laboratoire d'Astrophysique de Marseille

K. Isaak

European Space Research and Technology Centre (ESA ESTEC)

L. L. Kiss

Magyar Tudomanyos Akademia

K. W.F. Lam

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

J. Laskar

Observatoire de Paris

B. Lavie

Université de Genève

C. Lovis

Université de Genève

D. Magrin

Istituto nazionale di astrofisica (INAF)

L. Marafatto

Istituto nazionale di astrofisica (INAF)

P. Maxted

Keele University

S. McDermott

Protologic LLC

Djamel Mékarnia

Observatoire de la Cote d'Azur

C. Mordasini

Universität Bern

F. Murgas

Universidad de la Laguna

Valerio Nascimbeni

Istituto nazionale di astrofisica (INAF)

L. D. Nielsen

European Southern Observatory (ESO)

G. Olofsson

Stockholms universitet

R. Ottensamer

Universität Wien

I. Pagano

Istituto nazionale di astrofisica (INAF)

Enric Palle

Instituto de Astrofísica de Canarias

G. Peter

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

Giampaolo P. Piotto

Università di Padova

Don L. Pollacco

The University of Warwick

D. Queloz

University of Cambridge

Roberto Ragazzoni

Università di Padova

Devin Ramos

Union College

N. Rando

European Space Research and Technology Centre (ESA ESTEC)

H. Rauer

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

C. Reimers

Universität Wien

I. Ribas

Institut de Ciències de l'Espai (ICE) - CSIC

S. Seager

Massachusetts Institute of Technology (MIT)

D. Segransan

Université de Genève

Gaetano Scandariato

Istituto nazionale di astrofisica (INAF)

A.E. Simon

Universität Bern

A. M.S. Smith

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

M. Stalport

Universite de Liège

Manfred B. Steller

Institut fur Weltraumforschung

G.M. Szabó

Eötvös Loránd University (ELTE)

Nicolas Thomas

Universität Bern

T. Pritchard

NASA Goddard Space Flight Center

S. Udry

Université de Genève

C. Corral Van Damme

European Space Research and Technology Centre (ESA ESTEC)

V. Van Grootel

Universite de Liège

E. Villaver

Instituto de Astrofísica de Canarias

I. Walter

Deutsches Zentrums für Luft- und Raumfahrt (DLR)

N. A. Walton

University of Cambridge

Cristilyn N. Watkins

Harvard-Smithsonian Center for Astrophysics

Richard G West

The University of Warwick

Astronomy and Astrophysics

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

Vol. 685 A5

Ämneskategorier

Meteorologi och atmosfärforskning

Astronomi, astrofysik och kosmologi

DOI

10.1051/0004-6361/202348678

Mer information

Senast uppdaterat

2024-07-02