Discovery of two warm mini-Neptunes with contrasting densities orbiting the young K3V star TOI-815 - Observatoire de la Cote d'Azur Access content directly
Journal Articles Astronomy and Astrophysics - A&A Year : 2024

Discovery of two warm mini-Neptunes with contrasting densities orbiting the young K3V star TOI-815

Angelica Psaridi , Hugh Osborn , François Bouchy , Monika Lendl , Léna Parc , Nicolas Billot , Christopher Broeg , Sérgio Sousa , Vardan Adibekyan , Omar Attia , Andrea Bonfanti , Hritam Chakraborty , Karen Collins , Jeanne Davoult , Elisa Delgado-Mena , Nolan Grieves , Tristan Guillot (1) , Alexis Heitzmann , Ravit Helled , Coel Hellier , Jon Jenkins , Henrik Knierim , Andreas Krenn , Jack Lissauer , Rafael Luque , David Rapetti , Nuno Santos , Olga Suárez , Julia Venturini , Francis Wilkin , Thomas Wilson , Joshua Winn , Carl Ziegler , Tiziano Zingales , Yann Alibert , Alexis Brandeker , Jo Ann Egger , Davide Gandolfi , Matthew Hooton , Amy Tuson , Solène Ulmer-Moll , Lyu Abe , Romain Allart , Roi Alonso , David Anderson , Guillem Anglada Escudé , Tamas Bárczy , David Barrado , Susana Barros , Wolfgang Baumjohann , Mathias Beck , Thomas Beck , Willy Benz , Xavier Bonfils (2) , Luca Borsato , Vincent Bourrier , David Ciardi , Andrew Collier Cameron , Sébastien Charnoz (3) , Marion Cointepas , Szilárd Csizmadia , Patricio Cubillos , Gaspare Lo Curto , Melvyn Davies , Tansu Daylan , Magali Deleuil , Adrien Deline , Laetitia Delrez , Olivier Demangeon , Brice-Olivier Demory , Caroline Dorn , Xavier Dumusque , David Ehrenreich , Anders Erikson , Alain Lecavelier Des Etangs , Diana de Miguel , Andrea Fortier , Luca Fossati , Yolanda Frensch , Malcolm Fridlund , Michaël Gillon , Manuel Güdel , Maximilian Günther , Janis Hagelberg , Christiane Helling , Sergio Hoyer , Kate Isaak , Laszlo Kiss , Kristine Lam , Jacques Laskar (4) , Baptiste Lavie , Christophe Lovis , Demetrio Magrin , Luca Marafatto , Pierre Maxted , Scott Mcdermott , Djamel Mékarnia , Christoph Mordasini , Felipe Murgas , Valerio Nascimbeni , Louise Nielsen , Göran Olofsson , Roland Ottensamer , Isabella Pagano , Enric Pallé , Gisbert Peter , Giampaolo Piotto , Don Pollacco , Didier Queloz , Roberto Ragazzoni , Devin Ramos , Nicola Rando , Heike Rauer , Christian Reimers , Ignasi Ribas , Sara Seager , Damien Ségransan , Gaetano Scandariato , Attila Simon , Alexis Smith , Manu Stalport , Manfred Steller , Gyula Szabó , Nicolas Thomas , Tyler Pritchard , Stéphane Udry , Carlos Corral van Damme , Valérie van Grootel , Eva Villaver , Ingo Walter , Nicholas Walton , Cristilyn Watkins , Richard West
Angelica Psaridi
Hugh Osborn
François Bouchy
Monika Lendl
Léna Parc
Nicolas Billot
Christopher Broeg
Sérgio Sousa
Vardan Adibekyan
Omar Attia
Andrea Bonfanti
Hritam Chakraborty
Karen Collins
Jeanne Davoult
Elisa Delgado-Mena
Nolan Grieves
Tristan Guillot
Alexis Heitzmann
Ravit Helled
Coel Hellier
Jon Jenkins
Henrik Knierim
Andreas Krenn
Jack Lissauer
Rafael Luque
David Rapetti
Nuno Santos
Olga Suárez
Julia Venturini
Francis Wilkin
Thomas Wilson
Joshua Winn
Carl Ziegler
Tiziano Zingales
Yann Alibert
Alexis Brandeker
Jo Ann Egger
Davide Gandolfi
Matthew Hooton
Amy Tuson
Solène Ulmer-Moll
Lyu Abe
Romain Allart
Roi Alonso
David Anderson
Guillem Anglada Escudé
Tamas Bárczy
David Barrado
Susana Barros
Wolfgang Baumjohann
Mathias Beck
Thomas Beck
  • Function : Author
Willy Benz
Luca Borsato
Vincent Bourrier
David Ciardi
Andrew Collier Cameron
Sébastien Charnoz
Marion Cointepas
  • Function : Author
Szilárd Csizmadia
Patricio Cubillos
Gaspare Lo Curto
Melvyn Davies
Tansu Daylan
Magali Deleuil
Adrien Deline
  • Function : Author
Laetitia Delrez
Olivier Demangeon
Brice-Olivier Demory
Caroline Dorn
Xavier Dumusque
David Ehrenreich
Anders Erikson
  • Function : Author
Alain Lecavelier Des Etangs
Diana de Miguel
  • Function : Author
Andrea Fortier
Luca Fossati
Yolanda Frensch
Malcolm Fridlund
Michaël Gillon
Manuel Güdel
Maximilian Günther
Janis Hagelberg
Christiane Helling
Sergio Hoyer
Kate Isaak
Laszlo Kiss
Kristine Lam
Baptiste Lavie
Christophe Lovis
Demetrio Magrin
Luca Marafatto
Pierre Maxted
Scott Mcdermott
  • Function : Author
Djamel Mékarnia
Christoph Mordasini
Felipe Murgas
Valerio Nascimbeni
Louise Nielsen
Göran Olofsson
Roland Ottensamer
Isabella Pagano
Enric Pallé
Gisbert Peter
Giampaolo Piotto
Don Pollacco
Didier Queloz
Roberto Ragazzoni
Devin Ramos
Nicola Rando
  • Function : Author
Heike Rauer
Christian Reimers
Ignasi Ribas
Sara Seager
Damien Ségransan
Gaetano Scandariato
Attila Simon
Alexis Smith
Manu Stalport
Manfred Steller
Gyula Szabó
Nicolas Thomas
  • Function : Author
Tyler Pritchard
Stéphane Udry
Carlos Corral van Damme
Valérie van Grootel
Eva Villaver
Ingo Walter
Nicholas Walton
Cristilyn Watkins
Richard West

Abstract

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 −200 +400 Myr. TOI-8l5b 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-8l5c, 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 ⊕ ( ρ P = 1.64 −0.31 +0.33 g cm −3 ) and 23.5 ± 2.4 M ⊕ ( ρ P = 7.2 −1.0 +1.1 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 3 σ level. This emphasizes the peculiarity of the system’s orbital architecture, and probably hints at an eventful dynamical history.
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hal-04587518 , version 1 (27-05-2024)

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Angelica Psaridi, Hugh Osborn, François Bouchy, Monika Lendl, Léna Parc, et al.. Discovery of two warm mini-Neptunes with contrasting densities orbiting the young K3V star TOI-815. Astronomy and Astrophysics - A&A, 2024, 685, pp.A5. ⟨10.1051/0004-6361/202348678⟩. ⟨hal-04587518⟩
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