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 G. Sousa; Vardan Adibekyan; Mara Attia; Andrea Bonfanti; Hritam Chakraborty; Karen A. Collins; Jeanne Davoult; Elisa Delgado-Mena; Nolan Grieves; Tristan Guillot; Alexis Heitzmann; Ravit Helled; Coel Hellier; Jon M. Jenkins; Henrik Knierim; Andreas Krenn; Jack J. Lissauer; Rafael Luque; David Rapetti; Nuno C. Santos; Olga Suárez; Julia Venturini; Francis P. Wilkin; Thomas G. Wilson; Joshua N. Winn; Carl Ziegler; Tiziano Zingales; Yann Alibert; Alexis Brandeker; Jo Ann Egger; Davide Gandolfi; Matthew J. Hooton; Amy Tuson; Solène Ulmer-Moll; Lyu Abe; Romain Allart; Roi Alonso; David R. Anderson; Guillem Anglada Escudé; Tamas Bárczy; David Barrado; Susana C. C. Barros; Wolfgang Baumjohann; Mathias Beck; Thomas Beck; Willy Benz; Xavier Bonfils; Luca Borsato; Vincent Bourrier; David R. Ciardi; Andrew Collier Cameron; Sébastien Charnoz; Marion Cointepas; Szilárd Csizmadia; Patricio Cubillos; Gaspare Lo Curto; Melvyn B. Davies; Tansu Daylan; Magali Deleuil; Adrien Deline; Laetitia Delrez; Olivier D. S. Demangeon; Brice-Olivier Demory; Caroline Dorn; Xavier Dumusque; David Ehrenreich; Anders Erikson; Alain Lecavelier des Etangs; Diana de Miguel; Andrea Fortier; Luca Fossati; Yolanda G. C. Frensch; Malcolm Fridlund; Michaël Gillon; Manuel Güdel; Maximilian N. Günther; Janis Hagelberg; Christiane Helling; Sergio Hoyer; Kate G. Isaak; Laszlo L. Kiss; Kristine W. F. Lam; Jacques Laskar; Baptiste Lavie; Christophe Lovis; Demetrio Magrin; Luca Marafatto; Pierre Maxted; Scott McDermott; Djamel Mékarnia; Christoph Mordasini; Felipe Murgas; Valerio Nascimbeni; Louise D. 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 E. Simon; Alexis M. S. Smith; Manu Stalport; Manfred Steller; Gyula Szabó; Nicolas Thomas; Tyler A. Pritchard; Stéphane Udry; Carlos Corral Van Damme; Valérie Van Grootel; Eva Villaver; Ingo Walter; Nicholas Walton; Cristilyn N. Watkins; Richard G. West

doi:10.1051/0004-6361/202348678

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 G. Sousa, Vardan Adibekyan, Mara Attia, Andrea Bonfanti, Hritam Chakraborty, Karen A. Collins, Jeanne Davoult, Elisa Delgado-Mena, Nolan Grieves, Tristan Guillot, Alexis Heitzmann, Ravit Helled, Coel HellierJon M. Jenkins, Henrik Knierim, Andreas Krenn, Jack J. Lissauer, Rafael Luque, David Rapetti, Nuno C. Santos, Olga Suárez, Julia Venturini, Francis P. Wilkin, Thomas G. Wilson, Joshua N. Winn, Carl Ziegler, Tiziano Zingales, Yann Alibert, Alexis Brandeker, Jo Ann Egger, Davide Gandolfi, Matthew J. Hooton, Amy Tuson, Solène Ulmer-Moll, Lyu Abe, Romain Allart, Roi Alonso, David R. Anderson, Guillem Anglada Escudé, Tamas Bárczy, David Barrado, Susana C. C. Barros, Wolfgang Baumjohann, Mathias Beck, Thomas Beck, Willy Benz, Xavier Bonfils, Luca Borsato, Vincent Bourrier, David R. Ciardi, Andrew Collier Cameron, Sébastien Charnoz, Marion Cointepas, Szilárd Csizmadia, Patricio Cubillos, Gaspare Lo Curto, Melvyn B. Davies, Tansu Daylan, Magali Deleuil, Adrien Deline, Laetitia Delrez, Olivier D. S. Demangeon, Brice-Olivier Demory, Caroline Dorn, Xavier Dumusque, David Ehrenreich, Anders Erikson, Alain Lecavelier des Etangs, Diana de Miguel, Andrea Fortier, Luca Fossati, Yolanda G. C. Frensch, Malcolm Fridlund, Michaël Gillon, Manuel Güdel, Maximilian N. Günther, Janis Hagelberg, Christiane Helling, Sergio Hoyer, Kate G. Isaak, Laszlo L. Kiss, Kristine W. F. Lam, Jacques Laskar, Baptiste Lavie, Christophe Lovis, Demetrio Magrin, Luca Marafatto, Pierre Maxted, Scott McDermott, Djamel Mékarnia, Christoph Mordasini, Felipe Murgas, Valerio Nascimbeni, Louise D. 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 E. Simon, Alexis M. S. Smith, Manu Stalport, Manfred Steller, Gyula Szabó, Nicolas Thomas, Tyler A. Pritchard, Stéphane Udry, Carlos Corral Van Damme, Valérie Van Grootel, Eva Villaver, Ingo Walter, Nicholas Walton, Cristilyn N. Watkins, Richard G. West

Research output: Contribution to journal › Article › peer-review

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^+0.33g 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 3σ level. This emphasizes the peculiarity of the system’s orbital architecture, and probably hints at an eventful dynamical history.

Original language	English
Article number	A5
Number of pages	24
Journal	Astronomy & Astrophysics
Volume	685
Early online date	30 Apr 2024
DOIs	https://doi.org/10.1051/0004-6361/202348678
Publication status	Published - May 2024

Keywords

Techniques: photometric
Techniques: radial velocities
Planets and satellites: composition
Planets and satellites: detection
Planets and satellites: formation
Stars: individual: TOI-815

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https://arxiv.org/abs/2401.15709Licence: CC BY

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REVEAL: REVEALing Signatures of Habitable Worlds Hidden by Stellar Activity
Cameron, A. C. (PI)
UKRI (EU)
1/08/24 → 31/07/30
Project: Standard
AO2 - Professor Andrew Cameron: Project AO2 - Andrew Cameron
Cameron, A. C. (PI)
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TOI-815 light curves and RV sources
Psaridi, A. (Creator), Osborn, H. (Creator), Bouchy, F. (Creator), Lendl, M. (Creator), Parc, L. (Creator), Billot, N. (Creator), Broeg, C. (Creator), Sousa, S. G. (Creator), Adibekyan, V. (Creator), Attia, O. (Creator), Bonfanti, A. (Creator), Chakraborty, H. (Creator), Collins, K. A. (Creator), Davoult, J. (Creator), Delgado-Mena, E. (Creator), Grieves, N. (Creator), Guillot, T. (Creator), Heitzmann, A. (Creator), Helled, R. (Creator), Hellier, C. (Creator), Jenkins, J. M. (Creator), Knierim, H. (Creator), Krenn, A. (Creator), Lissauer, J. J. (Creator), Luque, R. (Creator), Rapetti, D. (Creator), Santos, N. C. (Creator), Suarez, O. (Creator), Venturini, J. (Creator), Wilkin, F. P. (Creator), Wilson, T. G. (Creator), Winn, J. N. (Creator), Ziegler, C. (Creator), Zingales, T. (Creator), Alibert, Y. (Creator), Brandeker, A. (Creator), Egger, J. A. (Creator), Gandolfi, D. (Creator), Hooton, M. J. (Creator), Tuson, A. (Creator), Ulmer-Moll, S. (Creator), Abe, L. (Creator), Allart, R. (Creator), Alonso, R. (Creator), Anderson, D. R. (Creator), Anglada Escude, G. (Creator), Barczy, T. (Creator), Barrado, D. (Creator), Barros, S. C. C. (Creator), Baumjohann, W. (Creator), Beck, M. (Creator), Beck, T. (Creator), Benz, W. (Creator), Bonfils, X. (Creator), Borsato, L. (Creator), Bourrier, V. (Creator), Ciardi, D. R. (Creator), Collier Cameron, A. (Creator), Charnoz, S. (Creator), Cointepas, M. (Creator), Csizmadia, S. (Creator), Cubillos, P. (Creator), Lo Curto, G. (Creator), Davies, M. B. (Creator), Daylan, T. (Creator), Deleuil, M. (Creator), Deline, A. (Creator), Delrez, L. (Creator), Demangeon, O. D. S. (Creator), Demory, B.-O. (Creator), Dorn, C. (Creator), Dumusque, X. (Creator), Ehrenreich, D. (Creator), Erikson, A. (Creator), Lecavelier Des Etangs, A. (Creator), De Miguel Ferreras, E. D. (Creator), Fortier, A. (Creator), Fossati, L. (Creator), Frensch, Y. G. C. (Creator), Fridlund, M. (Creator), Gillon, M. (Creator), Guedel, M. (Creator), Guenther, M. N. (Creator), Hagelberg, J. (Creator), Helling, C. (Creator), Hoyer, S. (Creator), Isaak, K. G. (Creator), Kiss, L. L. (Creator), Lam, K. (Creator), Laskar, J. (Creator), Lavie, B. (Creator), Lovis, C. (Creator), Magrin, D. (Creator), Marafatto, L. (Creator), Maxted, P. (Creator), McDermott, S. (Creator), Mekarnia, D. (Creator), Mordasini, C. (Creator), Murgas, F. (Creator), Nascimbeni, V. (Creator), Nielsen, L. D. (Creator), Olofsson, G. (Creator), Ottensamer, R. (Creator), Pagano, I. (Creator), Palle, E. (Creator), Peter, G. (Creator), Piotto, G. (Creator), Pollacco, D. (Creator), Queloz, D. (Creator), Ragazzoni, R. (Creator), Ramos, D. (Creator), Rando, N. (Creator), Rauer, H. (Creator), Reimers, C. (Creator), Ribas, I. (Creator), Seager, S. (Creator), Segransan, D. (Creator), Scandariato, G. (Creator), Simon, A. (Creator), Smith, A. (Creator), Stalport, M. (Creator), Steller, M. (Creator), Szabo, G. (Creator), Thomas, N. (Creator), Pritchard, T. A. (Creator), Udry, S. (Creator), Corral Van Damme, C. (Creator), Van Grootel, V. (Creator), Villaver, E. (Creator), Walter, I. (Creator), Walton, N. (Creator), Watkins, C. N. (Creator) & West, R. G. (Creator), Centre de Donnees Strasbourg (CDS), 2024
DOI: 10.26093/cds/vizier.36850005
Dataset

Cite this

Psaridi, A., Osborn, H., Bouchy, F., Lendl, M., Parc, L., Billot, N., Broeg, C., Sousa, S. G., Adibekyan, V., Attia, M., Bonfanti, A., Chakraborty, H., Collins, K. A., Davoult, J., Delgado-Mena, E., Grieves, N., Guillot, T., Heitzmann, A., Helled, R., ... West, R. G. (2024). Discovery of two warm mini-Neptunes with contrasting densities orbiting the young K3V star TOI-815. Astronomy & Astrophysics, 685, Article A5. https://doi.org/10.1051/0004-6361/202348678

@article{34a6064d8f94442e9fc000785ab426e7,

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

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⊕ (ρP = 1.64−0.31+0.33 g cm−3) and 23.5 ± 2.4 M⊕ (ρP = 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 3σ level. This emphasizes the peculiarity of the system{\textquoteright}s orbital architecture, and probably hints at an eventful dynamical history.",

keywords = "Techniques: photometric, Techniques: radial velocities, Planets and satellites: composition, Planets and satellites: detection, Planets and satellites: formation, Stars: individual: TOI-815",

author = "Angelica Psaridi and Hugh Osborn and Fran{\c c}ois Bouchy and Monika Lendl and L{\'e}na Parc and Nicolas Billot and Christopher Broeg and Sousa, {S{\'e}rgio G.} and Vardan Adibekyan and Mara Attia and Andrea Bonfanti and Hritam Chakraborty and Collins, {Karen A.} and Jeanne Davoult and Elisa Delgado-Mena and Nolan Grieves and Tristan Guillot and Alexis Heitzmann and Ravit Helled and Coel Hellier and Jenkins, {Jon M.} and Henrik Knierim and Andreas Krenn and Lissauer, {Jack J.} and Rafael Luque and David Rapetti and Santos, {Nuno C.} and Olga Su{\'a}rez and Julia Venturini and Wilkin, {Francis P.} and Wilson, {Thomas G.} and Winn, {Joshua N.} and Carl Ziegler and Tiziano Zingales and Yann Alibert and Alexis Brandeker and Egger, {Jo Ann} and Davide Gandolfi and Hooton, {Matthew J.} and Amy Tuson and Sol{\`e}ne Ulmer-Moll and Lyu Abe and Romain Allart and Roi Alonso and Anderson, {David R.} and Escud{\'e}, {Guillem Anglada} and Tamas B{\'a}rczy and David Barrado and Barros, {Susana C. C.} and Wolfgang Baumjohann and Mathias Beck and Thomas Beck and Willy Benz and Xavier Bonfils and Luca Borsato and Vincent Bourrier and Ciardi, {David R.} and Cameron, {Andrew Collier} and S{\'e}bastien Charnoz and Marion Cointepas and Szil{\'a}rd Csizmadia and Patricio Cubillos and {Lo Curto}, Gaspare and Davies, {Melvyn B.} and Tansu Daylan and Magali Deleuil and Adrien Deline and Laetitia Delrez and Demangeon, {Olivier D. S.} and Brice-Olivier Demory and Caroline Dorn and Xavier Dumusque and David Ehrenreich and Anders Erikson and {Lecavelier des Etangs}, Alain and {de Miguel}, Diana and Andrea Fortier and Luca Fossati and Frensch, {Yolanda G. C.} and Malcolm Fridlund and Micha{\"e}l Gillon and Manuel G{\"u}del and G{\"u}nther, {Maximilian N.} and Janis Hagelberg and Christiane Helling and Sergio Hoyer and Isaak, {Kate G.} and Kiss, {Laszlo L.} and Lam, {Kristine W. F.} and Jacques Laskar and Baptiste Lavie and Christophe Lovis and Demetrio Magrin and Luca Marafatto and Pierre Maxted and Scott McDermott and Djamel M{\'e}karnia and Christoph Mordasini and Felipe Murgas and Valerio Nascimbeni and Nielsen, {Louise D.} and G{\"o}ran Olofsson and Roland Ottensamer and Isabella Pagano and Enric Pall{\'e} and Gisbert Peter and Giampaolo Piotto and Don Pollacco and Didier Queloz and Roberto Ragazzoni and Devin Ramos and Nicola Rando and Heike Rauer and Christian Reimers and Ignasi Ribas and Sara Seager and Damien S{\'e}gransan and Gaetano Scandariato and Simon, {Attila E.} and Smith, {Alexis M. S.} and Manu Stalport and Manfred Steller and Gyula Szab{\'o} and Nicolas Thomas and Pritchard, {Tyler A.} and St{\'e}phane Udry and {Corral Van Damme}, Carlos and {Van Grootel}, Val{\'e}rie and Eva Villaver and Ingo Walter and Nicholas Walton and Watkins, {Cristilyn N.} and West, {Richard G.}",

note = "Funding: M.A. and V.B. have received funding from the European Research Council (ERC) under the European Union{\textquoteright}s Horizon 2020 research and innovation programme (project Spice Dune, grant agreement No 947634; grant agreement no. 730890). Co-funded by the European Union (ERC, FIERCE, 101052347). A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. P.M. acknowledges support from STFC research grant number ST/M001040/1. N.A.W. acknowledges UKSA grant ST/R004838/1. ",

year = "2024",

month = may,

doi = "10.1051/0004-6361/202348678",

language = "English",

volume = "685",

journal = "Astronomy & Astrophysics",

issn = "0004-6361",

publisher = "EDP SCIENCES S A",

}

Psaridi, A, Osborn, H, Bouchy, F, Lendl, M, Parc, L, Billot, N, Broeg, C, Sousa, SG, Adibekyan, V, Attia, M, Bonfanti, A, Chakraborty, H, Collins, KA, Davoult, J, Delgado-Mena, E, Grieves, N, Guillot, T, Heitzmann, A, Helled, R, Hellier, C, Jenkins, JM, Knierim, H, Krenn, A, Lissauer, JJ, Luque, R, Rapetti, D, Santos, NC, Suárez, O, Venturini, J, Wilkin, FP, Wilson, TG, Winn, JN, Ziegler, C, Zingales, T, Alibert, Y, Brandeker, A, Egger, JA, Gandolfi, D, Hooton, MJ, Tuson, A, Ulmer-Moll, S, Abe, L, Allart, R, Alonso, R, Anderson, DR, Escudé, GA, Bárczy, T, Barrado, D, Barros, SCC, Baumjohann, W, Beck, M, Beck, T, Benz, W, Bonfils, X, Borsato, L, Bourrier, V, Ciardi, DR, Cameron, AC, Charnoz, S, Cointepas, M, Csizmadia, S, Cubillos, P, Lo Curto, G, Davies, MB, Daylan, T, Deleuil, M, Deline, A, Delrez, L, Demangeon, ODS, Demory, B-O, Dorn, C, Dumusque, X, Ehrenreich, D, Erikson, A, Lecavelier des Etangs, A, de Miguel, D, Fortier, A, Fossati, L, Frensch, YGC, Fridlund, M, Gillon, M, Güdel, M, Günther, MN, Hagelberg, J, Helling, C, Hoyer, S, Isaak, KG, Kiss, LL, Lam, KWF, Laskar, J, Lavie, B, Lovis, C, Magrin, D, Marafatto, L, Maxted, P, McDermott, S, Mékarnia, D, Mordasini, C, Murgas, F, Nascimbeni, V, Nielsen, LD, Olofsson, G, Ottensamer, R, Pagano, I, Pallé, E, Peter, G, Piotto, G, Pollacco, D, Queloz, D, Ragazzoni, R, Ramos, D, Rando, N, Rauer, H, Reimers, C, Ribas, I, Seager, S, Ségransan, D, Scandariato, G, Simon, AE, Smith, AMS, Stalport, M, Steller, M, Szabó, G, Thomas, N, Pritchard, TA, Udry, S, Corral Van Damme, C, Van Grootel, V, Villaver, E, Walter, I, Walton, N, Watkins, CN & West, RG 2024, 'Discovery of two warm mini-Neptunes with contrasting densities orbiting the young K3V star TOI-815', Astronomy & Astrophysics, vol. 685, A5. https://doi.org/10.1051/0004-6361/202348678

TY - JOUR

T1 - Discovery of two warm mini-Neptunes with contrasting densities orbiting the young K3V star TOI-815

AU - Psaridi, Angelica

AU - Osborn, Hugh

AU - Bouchy, François

AU - Lendl, Monika

AU - Parc, Léna

AU - Billot, Nicolas

AU - Broeg, Christopher

AU - Sousa, Sérgio G.

AU - Adibekyan, Vardan

AU - Attia, Mara

AU - Bonfanti, Andrea

AU - Chakraborty, Hritam

AU - Collins, Karen A.

AU - Davoult, Jeanne

AU - Delgado-Mena, Elisa

AU - Grieves, Nolan

AU - Guillot, Tristan

AU - Heitzmann, Alexis

AU - Helled, Ravit

AU - Hellier, Coel

AU - Jenkins, Jon M.

AU - Knierim, Henrik

AU - Krenn, Andreas

AU - Lissauer, Jack J.

AU - Luque, Rafael

AU - Rapetti, David

AU - Santos, Nuno C.

AU - Suárez, Olga

AU - Venturini, Julia

AU - Wilkin, Francis P.

AU - Wilson, Thomas G.

AU - Winn, Joshua N.

AU - Ziegler, Carl

AU - Zingales, Tiziano

AU - Alibert, Yann

AU - Brandeker, Alexis

AU - Egger, Jo Ann

AU - Gandolfi, Davide

AU - Hooton, Matthew J.

AU - Tuson, Amy

AU - Ulmer-Moll, Solène

AU - Abe, Lyu

AU - Allart, Romain

AU - Alonso, Roi

AU - Anderson, David R.

AU - Escudé, Guillem Anglada

AU - Bárczy, Tamas

AU - Barrado, David

AU - Barros, Susana C. C.

AU - Baumjohann, Wolfgang

AU - Beck, Mathias

AU - Beck, Thomas

AU - Benz, Willy

AU - Bonfils, Xavier

AU - Borsato, Luca

AU - Bourrier, Vincent

AU - Ciardi, David R.

AU - Cameron, Andrew Collier

AU - Charnoz, Sébastien

AU - Cointepas, Marion

AU - Csizmadia, Szilárd

AU - Cubillos, Patricio

AU - Lo Curto, Gaspare

AU - Davies, Melvyn B.

AU - Daylan, Tansu

AU - Deleuil, Magali

AU - Deline, Adrien

AU - Delrez, Laetitia

AU - Demangeon, Olivier D. S.

AU - Demory, Brice-Olivier

AU - Dorn, Caroline

AU - Dumusque, Xavier

AU - Ehrenreich, David

AU - Erikson, Anders

AU - Lecavelier des Etangs, Alain

AU - de Miguel, Diana

AU - Fortier, Andrea

AU - Fossati, Luca

AU - Frensch, Yolanda G. C.

AU - Fridlund, Malcolm

AU - Gillon, Michaël

AU - Güdel, Manuel

AU - Günther, Maximilian N.

AU - Hagelberg, Janis

AU - Helling, Christiane

AU - Hoyer, Sergio

AU - Isaak, Kate G.

AU - Kiss, Laszlo L.

AU - Lam, Kristine W. F.

AU - Laskar, Jacques

AU - Lavie, Baptiste

AU - Lovis, Christophe

AU - Magrin, Demetrio

AU - Marafatto, Luca

AU - Maxted, Pierre

AU - McDermott, Scott

AU - Mékarnia, Djamel

AU - Mordasini, Christoph

AU - Murgas, Felipe

AU - Nascimbeni, Valerio

AU - Nielsen, Louise D.

AU - Olofsson, Göran

AU - Ottensamer, Roland

AU - Pagano, Isabella

AU - Pallé, Enric

AU - Peter, Gisbert

AU - Piotto, Giampaolo

AU - Pollacco, Don

AU - Queloz, Didier

AU - Ragazzoni, Roberto

AU - Ramos, Devin

AU - Rando, Nicola

AU - Rauer, Heike

AU - Reimers, Christian

AU - Ribas, Ignasi

AU - Seager, Sara

AU - Ségransan, Damien

AU - Scandariato, Gaetano

AU - Simon, Attila E.

AU - Smith, Alexis M. S.

AU - Stalport, Manu

AU - Steller, Manfred

AU - Szabó, Gyula

AU - Thomas, Nicolas

AU - Pritchard, Tyler A.

AU - Udry, Stéphane

AU - Corral Van Damme, Carlos

AU - Van Grootel, Valérie

AU - Villaver, Eva

AU - Walter, Ingo

AU - Walton, Nicholas

AU - Watkins, Cristilyn N.

AU - West, Richard G.

N1 - Funding: M.A. and V.B. have received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (project Spice Dune, grant agreement No 947634; grant agreement no. 730890). Co-funded by the European Union (ERC, FIERCE, 101052347). A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. P.M. acknowledges support from STFC research grant number ST/M001040/1. N.A.W. acknowledges UKSA grant ST/R004838/1.

PY - 2024/5

Y1 - 2024/5

N2 - 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⊕ (ρP = 1.64−0.31+0.33 g cm−3) and 23.5 ± 2.4 M⊕ (ρP = 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 3σ level. This emphasizes the peculiarity of the system’s orbital architecture, and probably hints at an eventful dynamical history.

AB - 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⊕ (ρP = 1.64−0.31+0.33 g cm−3) and 23.5 ± 2.4 M⊕ (ρP = 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 3σ level. This emphasizes the peculiarity of the system’s orbital architecture, and probably hints at an eventful dynamical history.

KW - Techniques: photometric

KW - Techniques: radial velocities

KW - Planets and satellites: composition

KW - Planets and satellites: detection

KW - Planets and satellites: formation

KW - Stars: individual: TOI-815

U2 - 10.1051/0004-6361/202348678

DO - 10.1051/0004-6361/202348678

M3 - Article

SN - 0004-6361

VL - 685

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

M1 - A5

ER -

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

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REVEAL: REVEALing Signatures of Habitable Worlds Hidden by Stellar Activity

AO2 - Professor Andrew Cameron: Project AO2 - Andrew Cameron

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TOI-815 light curves and RV sources

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