Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley★,★★
Journal article, 2024
TOI-732 is an M dwarf hosting two transiting planets that are located on the two opposite sides of the radius valley. Inferring a reliable demographics for this type of systems is key to understanding their formation and evolution mechanisms. Aims. By doubling the number of available space-based observations and increasing the number of radial velocity (RV) measurements, we aim at refining the parameters of TOI-732 b and c. We also use the results to study the slope of the radius valley and the density valley for a well-characterised sample of M-dwarf exoplanets. Methods. We performed a global Markov chain Monte Carlo analysis by jointly modelling ground-based light curves and CHEOPS and TESS observations, along with RV time series both taken from the literature and obtained with the MAROON-X spectrograph. The slopes of the M-dwarf valleys were quantified via a support vector machine (SVM) procedure. Results. TOI-732 b is an ultrashort-period planet (P = 0.76837931−+000000004200000039 days) with a radius Rb = 1.325+−00057058 R☉, a mass Mb = 2.46 ± 0.19 M☉, and thus a mean density ρb = 5.8+−1008 g cm−3, while the outer planet at P = 12.252284 ± 0.000013 days has Rc = 2.39+−001011 R☉, Mc = 8.04+−005048 M☉, and thus ρc = 3.24+−005543 g cm−3. Even with respect to the most recently reported values, this work yields uncertainties on the transit depths and on the RV semi-amplitudes that are smaller up to a factor of ∼1.6 and ∼2.4 for TOI-732 b and c, respectively. Our calculations for the interior structure and the location of the planets in the mass-radius diagram lead us to classify TOI-732 b as a super-Earth and TOI-732 c as a mini-Neptune. Following the SVM approach, we quantified d log Rp,valley/d log P = −0.065+−00024013, which is flatter than for Sun-like stars. In line with former analyses, we note that the radius valley for M-dwarf planets is more densely populated, and we further quantify the slope of the density valley as d log ρ̂valley/d log P = −0.02+−001204. Conclusions. Compared to FGK stars, the weaker dependence of the position of the radius valley on the orbital period might indicate that the formation shapes the radius valley around M dwarfs more strongly than the evolution mechanisms.
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planets and satellites: fundamental parameters
techniques: radial velocities
stars: fundamental parameters
techniques: photometric
Author
A. Bonfanti
Institut fur Weltraumforschung
M. Brady
University of Chicago
T.G. Wilson
The University of Warwick
J. Venturini
University of Geneva
J. A. Egger
University of Bern
A. Brandeker
Stockholm University
S. G. Sousa
University of Porto
M. Lendl
University of Geneva
A.E. Simon
University of Bern
D. Queloz
Swiss Federal Institute of Technology in Zürich (ETH)
University of Cambridge
G. Olofsson
Stockholm University
V. Adibekyan
University of Porto
Y. Alibert
University of Bern
L. Fossati
Institut fur Weltraumforschung
M.J. Hooton
University of Cambridge
D. Kubyshkina
Institut fur Weltraumforschung
R. Luque
University of Chicago
F. Murgas
University of La Laguna
Instituto de Astrofísica de Canarias
A. J. Mustill
Lund University
N. C. Santos
University of Porto
V. Van Grootel
University of Liège
R. Alonso
Instituto de Astrofísica de Canarias
University of La Laguna
J. Asquier
European Space Research and Technology Centre (ESA ESTEC)
T. Bandy
University of Bern
T. Bárczy
Admatis
D. Barrado Navascues
Centro de Astrobiologia (CAB)
S.C.C. Barros
University of Porto
W. Baumjohann
Institut fur Weltraumforschung
Jacob L. Bean
University of Chicago
M. Beck
University of Geneva
T. Beck
University of Bern
W. Benz
University of Bern
M. Bergomi
Istituto nazionale di astrofisica (INAF)
N. Billot
University of Geneva
L. Borsato
Istituto nazionale di astrofisica (INAF)
C. Broeg
University of Bern
A. Collier Cameron
University of St Andrews
Szilard Csizmadia
German Aerospace Center (DLR)
P. E. Cubillos
Institut fur Weltraumforschung
Istituto nazionale di astrofisica (INAF)
M. B. Davies
Lund University
M. Deleuil
Laboratoire d'Astrophysique de Marseille
A. Deline
University of Geneva
L. Delrez
University of Liège
O. Demangeon
University of Porto
B.O. Demory
University of Bern
D. Ehrenreich
University of Geneva
Anders Erikson
German Aerospace Center (DLR)
A. Fortier
University of Bern
Malcolm Fridlund
Leiden University
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
D. Gandolfi
University of Turin
Michaël Gillon
University of Liège
M. Gudel
University of Vienna
Maximilian N. Günther
European Space Research and Technology Centre (ESA ESTEC)
A. Heitzmann
University of Geneva
Ch. Helling
Technische Universität Graz
Institut fur Weltraumforschung
S. Hoyer
Laboratoire d'Astrophysique de Marseille
K. Isaak
European Space Research and Technology Centre (ESA ESTEC)
D. Kasper
University of Chicago
L. L. Kiss
Eötvös Loránd University (ELTE)
Hungarian Academy of Sciences
K. W.F. Lam
German Aerospace Center (DLR)
J. Laskar
Paris Observatory
A. L. des Etangs
Institut d 'Astrophysique de Paris
D. Magrin
Istituto nazionale di astrofisica (INAF)
P. Maxted
Keele University
C. Mordasini
University of Bern
Valerio Nascimbeni
Istituto nazionale di astrofisica (INAF)
R. Ottensamer
University of Vienna
I. Pagano
Istituto nazionale di astrofisica (INAF)
Enric Palle
Instituto de Astrofísica de Canarias
University of La Laguna
G. Peter
German Aerospace Center (DLR)
Giampaolo P. Piotto
University of Padua
Istituto nazionale di astrofisica (INAF)
D. Pollacco
The University of Warwick
R. Ragazzoni
Istituto nazionale di astrofisica (INAF)
University of Padua
N. Rando
European Space Research and Technology Centre (ESA ESTEC)
H. Rauer
Freie Universität Berlin
German Aerospace Center (DLR)
Technische Universität Berlin
I. Ribas
Spanish National Research Council (CSIC)
Centre Tecnològic de Telecomunicacions de Catalunya (CTTC)
Gaetano Scandariato
Istituto nazionale di astrofisica (INAF)
D. Segransan
University of Geneva
A. Seifahrt
University of Chicago
A. M.S. Smith
German Aerospace Center (DLR)
M. Stalport
University of Liège
G. Stefánsson
Princeton University
M. Steinberger
Institut fur Weltraumforschung
J. Stürmer
Heidelberg-Königstuhl State Observatory
G.M. Szabó
Eötvös Loránd University (ELTE)
Nicolas Thomas
University of Bern
S. Udry
University of Geneva
E. Villaver
University of La Laguna
Instituto de Astrofísica de Canarias
N. A. Walton
University of Cambridge
K. Westerdorff
German Aerospace Center (DLR)
Tiziano Zingales
University of Padua
Istituto nazionale di astrofisica (INAF)
Published in
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 682 art. no A66Categorizing
Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Identifiers
DOI
10.1051/0004-6361/202348180