An Ultra-Short Period Super-Earth and Sub-Neptune Spanning the Radius Valley Orbiting the Kinematic Thick Disk Star TOI-2345
Authors
Yoshi Nike Emilia Eschen
Thomas G. Wilson
Andrea Bonfanti
Carina M. Persson
Sérgio G. Sousa
Monika Lendl
Alexis Heitzmann
Attila E. Simon
Göran Olofsson
Amadeo Castro-González
Jo Ann Egger
Luca Fossati
Alexander James Mustill
Hugh P. Osborn
Hugo G. Vivien
Yann Alibert
Roi Alonso
Tamas Bárczy
David Barrado
Susana C. C. Barros
Wolfgang Baumjohann
Willy Benz
Nicolas Billot
Luca Borsato
Alexis Brandeker
Christopher Broeg
Maximilian Buder
Douglas A. Caldwell
Andrew Collier Cameron
Alexandre C. M. Correia
Szilard Csizmadia
Patricio E. Cubillos
Melvyn B. Davies
Magali Deleuil
Adrien Deline
Olivier D. S. Demangeon
Brice-Olivier Demory
Aliz Derekas
Billy Edwards
David Ehrenreich
Anders Erikson
Jacopo Farinato
Andrea Fortier
Malcolm Fridlund
Davide Gandolfi
Kosmas Gazeas
Michaël Gillon
Robert Goeke
Manuel Güdel
Maximilian N. Günther
Johann Hasiba
Ch. Helling
Kate G. Isaak
Jon M. Jenkins
Tatiana Keller
Laszlo L. Kiss
Daniel Kitzmann
Judith Korth
Kristine W. F. Lam
Jacques Laskar
Alain Lecavelier des Etangs
Adrien Leleu
Demetrio Magrin
Pierre F. L. Maxted
Bruno Merín
Christoph Mordasini
Valerio Nascimbeni
Roland Ottensamer
Isabella Pagano
Enric Pallé
Gisbert Peter
Daniele Piazza
Giampaolo Piotto
Don Pollacco
Didier Queloz
Roberto Ragazzoni
Nicola Rando
Francesco Ratti
Heike Rauer
Ignasi Ribas
Nuno C. Santos
Gaetano Scandariato
Damien Ségransan
Avi Shporer
Alexis M. S. Smith
Manu Stalport
Sophia Sulis
Gyula M. Szabó
Stéphane Udry
Solène Ulmer-Moll
Valérie Van Grootel
Julia Venturini
Eva Villaver
Nicholas A. Walton
David Watanabe
Sebastian Wolf
Carl Ziegler
Abstract
A crucial chemical link between stars and their orbiting exoplanets is thought to exist. If universal, this connection could affect the formation and evolution of all planets. Therefore, this potential vital link needs testing by characterising exoplanets around chemically-diverse stars. We present the discovery of two planets orbiting the metal-poor, kinematic thick-disk K-dwarf TOI-2345. TOI-2345 b is a super-Earth with a period of 1.05 days and TOI-2345 c is a sub-Neptune with a period of 21 days. In addition to the target being observed in 4 TESS sectors, we obtained 5 CHEOPS visits and 26 radial velocities from HARPS. By conducting a joint analysis of all the data, we find TOI-2345 b to have a radius of $1.504\substack{+0.047\\-0.044}$ R$_\oplus$ and a mass of $3.49\pm0.85$ M$_\oplus$; and TOI-2345 c to have a radius of $2.451\substack{+0.045\\-0.046}$ R$_\oplus$ and a mass of $7.27\substack{+2.27\\-2.45}$ M$_\oplus$. To explore chemical links between these planets and their host star, we model their interior structures newly accounting for devolatised stellar abundances. TOI-2345 adds to the limited sample of well characterised planetary systems around thick disk stars. This system challenges theories of formation and populations of planets around thick disk stars with its Ultra-Short Period super-Earth and the wide period distribution of these two planets spanning the radius valley.
