Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley

A. Bonfanti; M. Brady; T. G. Wilson; J. Venturini; J. A. Egger; A. Brandeker; S. G. Sousa; M. Lendl; A. E. Simon; D. Queloz; G. Olofsson; V. Adibekyan; Y. Alibert; L. Fossati; M. J. Hooton; D. Kubyshkina; R. Luque; F. Murgas; A. J. Mustill; N. C. Santos; V. Van Grootel; R. Alonso; J. Asquier; T. Bandy; T. Bárczy; D. Barrado Navascues; S. C.C. Barros; W. Baumjohann; J. Bean; M. Beck; T. Beck; W. Benz; M. Bergomi; N. Billot; L. Borsato; C. Broeg; A. Collier Cameron; Sz Csizmadia; P. E. Cubillos; M. B. Davies; M. Deleuil; A. Deline; L. Delrez; O. D.S. Demangeon; B. O. Demory; D. Ehrenreich; A. Erikson; A. Fortier; M. Fridlund; D. Gandolfi; M. Gillon; M. Güdel; M. N. Günther; A. Heitzmann; Ch Helling; S. Hoyer; K. G. Isaak; D. Kasper; L. L. Kiss; K. W.F. Lam; J. Laskar; A. Lecavelier des Etangs; D. Magrin; P. F.L. Maxted; C. Mordasini; V. Nascimbeni; R. Ottensamer; I. Pagano; E. Pallé; G. Peter; G. Piotto; D. Pollacco; R. Ragazzoni; N. Rando; H. Rauer; I. Ribas; G. Scandariato; D. Ségransan; A. Seifahrt; A. M.S. Smith; M. Stalport; G. Stefánsson; M. Steinberger; J. Stürmer; Gy M. Szabó; N. Thomas; S. Udry; E. Villaver; N. A. Walton; K. Westerdorff; T. Zingales

doi:10.1051/0004-6361/202348180

Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley

A. Bonfanti, M. Brady, T. G. Wilson, J. Venturini, J. A. Egger, A. Brandeker, S. G. Sousa, M. Lendl, A. E. Simon, D. Queloz, G. Olofsson, V. Adibekyan, Y. Alibert, L. Fossati, M. J. Hooton, D. Kubyshkina, R. Luque, F. Murgas, A. J. Mustill, N. C. SantosV. Van Grootel, R. Alonso, J. Asquier, T. Bandy, T. Bárczy, D. Barrado Navascues, S. C.C. Barros, W. Baumjohann, J. Bean, M. Beck, T. Beck, W. Benz, M. Bergomi, N. Billot, L. Borsato, C. Broeg, A. Collier Cameron, Sz Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, A. Deline, L. Delrez, O. D.S. Demangeon, B. O. Demory, D. Ehrenreich, A. Erikson, A. Fortier, M. Fridlund, D. Gandolfi, M. Gillon, M. Güdel, M. N. Günther, A. Heitzmann, Ch Helling, S. Hoyer, K. G. Isaak, D. Kasper, L. L. Kiss, K. W.F. Lam, J. Laskar, A. Lecavelier des Etangs, D. Magrin, P. F.L. Maxted, C. Mordasini, V. Nascimbeni, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, G. Scandariato, D. Ségransan, A. Seifahrt, A. M.S. Smith, M. Stalport, G. Stefánsson, M. Steinberger, J. Stürmer, Gy M. Szabó, N. Thomas, S. Udry, E. Villaver, N. A. Walton, K. Westerdorff, T. Zingales

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

Abstract

Context. 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-732b is an ultrashort-period planet (P = 0.76837931_-0.00000042^+0.0000039days) with a radius R_b = 1.325_-0.058^+0.057R_⊕, a mass M_b = 2.46 ± 0.19 M_⊕, and thus a mean density ρ_b = 5.8_-0.8^+1.0 g cm^-3, while the outer planet at P = 12.252284 ± 0.000013 days has R_c = 2.39_-0.11^+0.10R_⊕, M_c = 8.04_-0.48^+0.50M_⊕, and thus ρ_c = 3.24_-0.43^+0.55 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 R_p,valley / d logP = -0.065_-0.013^+0.024, 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 ρˆ_valley / d log P = -0.02_-0.04^+0.12.

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.

Original language	English
Article number	A66
Number of pages	28
Journal	Astronomy and Astrophysics
Volume	682
DOIs	https://doi.org/10.1051/0004-6361/202348180
Publication status	Published - 1 Feb 2024

Keywords

Planets and satellites: fundamental parameters
Stars: fundamental parameters
Techniques: photometric
Techniques: radial velocities

Access to Document

10.1051/0004-6361/202348180Licence: CC BY

AO2 - Professor Andrew Cameron: Project AO2 - Andrew Cameron
Cameron, A. C. (PI)
Science & Technology Facilities Council
1/04/21 → 31/03/24
Project: Standard
Astronomy at St Andrews 2018-2021: Astronomy at St Andrews 2018-2021
Jardine, M. M. (PI), Bonnell, I. A. (CoI), Cameron, A. C. (CoI), Cyganowski, C. J. (CoI), Dominik, M. (CoI), Helling, C. (CoI), Horne, K. D. (CoI), Scholz, A. (CoI), Tojeiro, R. (CoI), Weijmans, A.-M. (CoI), Wild, V. (CoI), Woitke, P. (CoI), Wood, K. (CoI) & Zhao, H. (CoI)
1/04/18 → 31/03/22
Project: Standard
Support for the PLATO Development: Support for the PLATO Development Phase 2017-2022: Planet candidate ranking and validation
Cameron, A. C. (PI)
Science & Technology Facilities Council
1/08/17 → 31/12/22
Project: Standard

TOI-732 TESS and CHEOPS detrended light curves
Bonfanti, A. (Creator), Brady, M. (Creator), Wilson, T. G. (Creator), Venturini, J. (Creator), Egger, J. A. (Creator), Brandeker, A. (Creator), Sousa, S. G. (Creator), Lendl, M. (Creator), Simon, A. E. (Creator), Queloz, D. (Creator), Olofsson, G. (Creator), Adibekyan, V. (Creator), Alibert, Y. (Creator), Fossati, L. (Creator), Hooton, M. J. (Creator), Kubyshkina, D. (Creator), Luque, R. (Creator), Murgas, F. (Creator), Mustill, A. J. (Creator), Santos, N. C. (Creator), Van Grootel, V. (Creator), Alonso, R. (Creator), Asquier, J. (Creator), Bandy, T. (Creator), Barczy, T. (Creator), Barrado Navascues, D. (Creator), Barros, S. C. C. (Creator), Baumjohann, W. (Creator), Bean, J. (Creator), Beck, M. (Creator), Beck, T. (Creator), Benz, W. (Creator), Bergomi, M. (Creator), Billot, N. (Creator), Borsato, L. (Creator), Broeg, C. (Creator), Collier Cameron, A. (Creator), Sz, C. (Creator), Cubillos, P. E. (Creator), Davies, M. B. (Creator), Deleuil, M. (Creator), Deline, A. (Creator), Delrez, L. (Creator), Demangeon, O. D. S. (Creator), Demory, B.-O. (Creator), Ehrenreich, D. (Creator), Erikson, A. (Creator), Fortier, A. (Creator), Fridlund, M. (Creator), Gandolfi, D. (Creator), Gillon, M. (Creator), Guedel, M. (Creator), Guenther, M. N. (Creator), Heitzmann, A. (Creator), Helling, C. (Creator), Hoyer, S. (Creator), Isaak, K. G. (Creator), Kasper, D. (Creator), Kiss, L. L. (Creator), K.W.F., L. (Creator), Laskar, J. (Creator), Lecavelier Des Etangs, A. (Creator), Magrin, D. (Creator), Maxted, P. F. L. (Creator), Mordasini, C. (Creator), Nascimbeni, V. (Creator), Ottensamer, R. (Creator), Pagano, I. (Creator), Palle, E. (Creator), Peter, G. (Creator), Piotto, G. (Creator), Pollacco, D. (Creator), Ragazzoni, R. (Creator), Rando, N. (Creator), Rauer, H. (Creator), Ribas, I. (Creator), Scandariato, G. (Creator), Segransan, D. (Creator), Seifahrt, A. (Creator), Smith, A. M. S. (Creator), Stalport, M. (Creator), Stefansson, G. (Creator), Steinberger, M. (Creator), Stuermer, J. (Creator), GyM., S. (Creator), Thomas, N. (Creator), Udry, S. (Creator), Villaver, E. (Creator), Walton, N. A. (Creator), Westerdorff, K. (Creator) & Zingales, T. (Creator), Centre de Donnees Strasbourg (CDS), 2024
DOI: 10.26093/cds/vizier.36820066
Dataset

Cite this

Bonfanti, A., Brady, M., Wilson, T. G., Venturini, J., Egger, J. A., Brandeker, A., Sousa, S. G., Lendl, M., Simon, A. E., Queloz, D., Olofsson, G., Adibekyan, V., Alibert, Y., Fossati, L., Hooton, M. J., Kubyshkina, D., Luque, R., Murgas, F., Mustill, A. J., ... Zingales, T. (2024). Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley. Astronomy and Astrophysics, 682, Article A66. https://doi.org/10.1051/0004-6361/202348180

@article{57044cc2440346f297b181a5edb4b6b5,

title = "Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley",

abstract = "Context. 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-732b is an ultrashort-period planet (P = 0.76837931-0.00000042+0.0000039 days) with a radius Rb = 1.325-0.058+0.057R⊕, a mass Mb = 2.46 ± 0.19 M⊕, and thus a mean density ρb = 5.8-0.8+1.0 g cm-3, while the outer planet at P = 12.252284 ± 0.000013 days has Rc = 2.39-0.11+0.10R⊕, Mc = 8.04-0.48+0.50M⊕, and thus ρc = 3.24-0.43+0.55 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 logP = -0.065-0.013+0.024, 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 ρˆvalley / d log P = -0.02-0.04+0.12.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.",

keywords = "Planets and satellites: fundamental parameters, Stars: fundamental parameters, Techniques: photometric, Techniques: radial velocities",

author = "A. Bonfanti and M. Brady and Wilson, {T. G.} and J. Venturini and Egger, {J. A.} and A. Brandeker and Sousa, {S. G.} and M. Lendl and Simon, {A. E.} and D. Queloz and G. Olofsson and V. Adibekyan and Y. Alibert and L. Fossati and Hooton, {M. J.} and D. Kubyshkina and R. Luque and F. Murgas and Mustill, {A. J.} and Santos, {N. C.} and {Van Grootel}, V. and R. Alonso and J. Asquier and T. Bandy and T. B{\'a}rczy and Navascues, {D. Barrado} and Barros, {S. C.C.} and W. Baumjohann and J. Bean and M. Beck and T. Beck and W. Benz and M. Bergomi and N. Billot and L. Borsato and C. Broeg and Cameron, {A. Collier} and Sz Csizmadia and Cubillos, {P. E.} and Davies, {M. B.} and M. Deleuil and A. Deline and L. Delrez and Demangeon, {O. D.S.} and Demory, {B. O.} and D. Ehrenreich and A. Erikson and A. Fortier and M. Fridlund and D. Gandolfi and M. Gillon and M. G{\"u}del and G{\"u}nther, {M. N.} and A. Heitzmann and Ch Helling and S. Hoyer and Isaak, {K. G.} and D. Kasper and Kiss, {L. L.} and Lam, {K. W.F.} and J. Laskar and {des Etangs}, {A. Lecavelier} and D. Magrin and Maxted, {P. F.L.} and C. Mordasini and V. Nascimbeni and R. Ottensamer and I. Pagano and E. Pall{\'e} and G. Peter and G. Piotto and D. Pollacco and R. Ragazzoni and N. Rando and H. Rauer and I. Ribas and G. Scandariato and D. S{\'e}gransan and A. Seifahrt and Smith, {A. M.S.} and M. Stalport and G. Stef{\'a}nsson and M. Steinberger and J. St{\"u}rmer and Szab{\'o}, {Gy M.} and N. Thomas and S. Udry and E. Villaver and Walton, {N. A.} and K. Westerdorff and T. Zingales",

note = "Funding: CHEOPS is an ESA mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. The CHEOPS Consortium would like to gratefully acknowledge the support received by all the agencies, offices, universities, and industries involved. Their flexibility and willingness to explore new approaches were essential to the success of this mission. CHEOPS data analysed in this article will be made available in the CHEOPS mission archive ( https://cheops.unige.ch/archive_browser/ ). T.Wi. acknowledges support from the UKSA and the University of Warwick. This work has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grants 51NF40_182901 and 51NF40_205606. A.Br. was supported by the SNSA. S.G.S. acknowledge support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. A.Si. and C.Br. acknowledge support from the Swiss Space Office through the ESA PRODEX program. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). Y.Al. acknowledges support from the Swiss National Science Foundation (SNSF) under grant 200020_192038. N.C.Sa. acknowledges funding by the European Union (ERC, FIERCE, 101052347). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. V.V.G. is an F.R.S-FNRS Research Associate. R.Al., D.Ba., E.Pa., and I.Ri. acknowledge financial support from the Agencia Estatal de Investigaci\u00F3n of the Ministerio de Ciencia e Innovaci\u00F3n MCIN/AEI/10.13039/501100011033 and the ERDF \u201CA way of making Europe\u201D through projects PID2019-107061GB-C61, PID2019-107061GB-C66, PID2021-125627OB-C31, and PID2021-125627OB-C32, from the Centre of Excellence \u201CSevero Ochoa\u201D award to the Instituto de Astrof\u00EDsica de Canarias (CEX2019-000920-S), from the Centre of Excellence \u201CMar\u00EDa de Maeztu\u201D award to the Institut de Ci\u00E8ncies de l\u2019Espai (CEX2020-001058-M), and from the Generalitat de Catalunya/CERCA programme. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. L.Bo., V.Na., I.Pa., G.Pi., R.Ra., G.Sc., and T.Zi. acknowledge support from CHEOPS ASI-INAF agreement no. 2019-29-HH.0. 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.E.C. is funded by the Austrian Science Fund (FWF) Erwin Schroedinger Fellowship, program J4595-N. This project was supported by the CNES. The Belgian participation to CHEOPS has been supported by the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Program, and by the University of Li\u00E8ge through an ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. L.D. is an F.R.S.-FNRS Postdoctoral Researcher. This work was supported by FCT \u2013 Funda\u00E7\u00E3o para a Ci\u00EAncia e a Tecnologia through national funds and by FEDER through COMPETE2020 through the research grants UIDB/04434/2020, UIDP/04434/2020, 2022.06962.PTDC. O.D.S.D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B.-O.D. acknowledges support from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number MB22.00046. This project has received funding from the European Research Council (ERC) under the European Union\u2019s Horizon 2020 research and innovation programme (project F OUR A CES . grant agreement no. 724427). It has also been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D.E. acknowledges financial support from the Swiss National Science Foundation for project 200021_200726. M.F. and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18). A.J.M. acknowledges support from the Swedish National Space Agency (120/19C). D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 \u201CGaseousor rocky? Unveiling the nature of small worlds\u201D. M.G. is an F.R.S.-FNRS Senior Research Associate. M.N.G. is the ESA CHEOPS Project Scientist and Mission Representative, and as such also responsible for the Guest Observers (GO) Programme. M.N.G. does not relay proprietary information between the GO and Guaranteed Time Observation (GTO) Programmes, and does not decide on the definition and target selection of the GTO Programme. C.He. acknowledges support from the European Union H2020-MSCA-ITN-2019 under Grant Agreement no. 860470 (CHAMELEON). S.H. gratefully acknowledges CNES funding through the grant 837319. K.G.I. is the ESA CHEOPS Project Scientist and is responsible for the ESA CHEOPS Guest Observers Programme. She does not participate in, or contribute to, the definition of the Guaranteed Time Programme of the CHEOPS mission through which observations described in this paper have been taken, nor to any aspect of target selection for the programme. K.W.F.L. was supported by Deutsche Forschungsgemeinschaft grants RA714/14-1 within the DFG Schwerpunkt SPP 1992, Exploring the Diversity of Extrasolar Planets. This work was granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d\u2019Avenir supervised by the Agence Nationale pour la Recherche. P.M. acknowledges support from STFC research grant number ST/M001040/1. G.S. acknowledges support provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51519.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Gy.M.Sz. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a a PRODEX Experiment Agreement No. 4000137122, the Lend\u00FClet LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. N.A.W. acknowledges UKSA grant ST/R004838/1. R.L. acknowledges funding from University of La Laguna through the Margarita Salas Fellowship from the Spanish Ministry of Universities ref. UNI/551/2021-May 26, and under the EU Next Generation funds. This work has made use of data from the European Space Agency (ESA) mission Gaia ( https://www.cosmos.esa.int/gaia ), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium ). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This article is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos S\u00E1nchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This work is partly financed by the Spanish Ministry of Economics and Competitiveness through grants PGC2018-098153-B-C31. This work is partly supported by JSPS KAKENHI Grant Numbers JP17H04574, JP18H01265, and JP18H05439, Grant-in-Aid for JSPS Fellows Grant Number JP20J21872, JST PRESTO Grant Number JPMJPR1775, and a University Research Support Grant from the National Astronomical Observatory of Japan (NAOJ). This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE 1746045.",

year = "2024",

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doi = "10.1051/0004-6361/202348180",

language = "English",

volume = "682",

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Bonfanti, A, Brady, M, Wilson, TG, Venturini, J, Egger, JA, Brandeker, A, Sousa, SG, Lendl, M, Simon, AE, Queloz, D, Olofsson, G, Adibekyan, V, Alibert, Y, Fossati, L, Hooton, MJ, Kubyshkina, D, Luque, R, Murgas, F, Mustill, AJ, Santos, NC, Van Grootel, V, Alonso, R, Asquier, J, Bandy, T, Bárczy, T, Navascues, DB, Barros, SCC, Baumjohann, W, Bean, J, Beck, M, Beck, T, Benz, W, Bergomi, M, Billot, N, Borsato, L, Broeg, C, Cameron, AC, Csizmadia, S, Cubillos, PE, Davies, MB, Deleuil, M, Deline, A, Delrez, L, Demangeon, ODS, Demory, BO, Ehrenreich, D, Erikson, A, Fortier, A, Fridlund, M, Gandolfi, D, Gillon, M, Güdel, M, Günther, MN, Heitzmann, A, Helling, C, Hoyer, S, Isaak, KG, Kasper, D, Kiss, LL, Lam, KWF, Laskar, J, des Etangs, AL, Magrin, D, Maxted, PFL, Mordasini, C, Nascimbeni, V, Ottensamer, R, Pagano, I, Pallé, E, Peter, G, Piotto, G, Pollacco, D, Ragazzoni, R, Rando, N, Rauer, H, Ribas, I, Scandariato, G, Ségransan, D, Seifahrt, A, Smith, AMS, Stalport, M, Stefánsson, G, Steinberger, M, Stürmer, J, Szabó, GM, Thomas, N, Udry, S, Villaver, E, Walton, NA, Westerdorff, K & Zingales, T 2024, 'Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley', Astronomy and Astrophysics, vol. 682, A66. https://doi.org/10.1051/0004-6361/202348180

TY - JOUR

T1 - Characterising TOI-732 b and c

T2 - New insights into the M-dwarf radius and density valley

AU - Bonfanti, A.

AU - Brady, M.

AU - Wilson, T. G.

AU - Venturini, J.

AU - Egger, J. A.

AU - Brandeker, A.

AU - Sousa, S. G.

AU - Lendl, M.

AU - Simon, A. E.

AU - Queloz, D.

AU - Olofsson, G.

AU - Adibekyan, V.

AU - Alibert, Y.

AU - Fossati, L.

AU - Hooton, M. J.

AU - Kubyshkina, D.

AU - Luque, R.

AU - Murgas, F.

AU - Mustill, A. J.

AU - Santos, N. C.

AU - Van Grootel, V.

AU - Alonso, R.

AU - Asquier, J.

AU - Bandy, T.

AU - Bárczy, T.

AU - Navascues, D. Barrado

AU - Barros, S. C.C.

AU - Baumjohann, W.

AU - Bean, J.

AU - Beck, M.

AU - Beck, T.

AU - Benz, W.

AU - Bergomi, M.

AU - Billot, N.

AU - Borsato, L.

AU - Broeg, C.

AU - Cameron, A. Collier

AU - Csizmadia, Sz

AU - Cubillos, P. E.

AU - Davies, M. B.

AU - Deleuil, M.

AU - Deline, A.

AU - Delrez, L.

AU - Demangeon, O. D.S.

AU - Demory, B. O.

AU - Ehrenreich, D.

AU - Erikson, A.

AU - Fortier, A.

AU - Fridlund, M.

AU - Gandolfi, D.

AU - Gillon, M.

AU - Güdel, M.

AU - Günther, M. N.

AU - Heitzmann, A.

AU - Helling, Ch

AU - Hoyer, S.

AU - Isaak, K. G.

AU - Kasper, D.

AU - Kiss, L. L.

AU - Lam, K. W.F.

AU - Laskar, J.

AU - des Etangs, A. Lecavelier

AU - Magrin, D.

AU - Maxted, P. F.L.

AU - Mordasini, C.

AU - Nascimbeni, V.

AU - Ottensamer, R.

AU - Pagano, I.

AU - Pallé, E.

AU - Peter, G.

AU - Piotto, G.

AU - Pollacco, D.

AU - Ragazzoni, R.

AU - Rando, N.

AU - Rauer, H.

AU - Ribas, I.

AU - Scandariato, G.

AU - Ségransan, D.

AU - Seifahrt, A.

AU - Smith, A. M.S.

AU - Stalport, M.

AU - Stefánsson, G.

AU - Steinberger, M.

AU - Stürmer, J.

AU - Szabó, Gy M.

AU - Thomas, N.

AU - Udry, S.

AU - Villaver, E.

AU - Walton, N. A.

AU - Westerdorff, K.

AU - Zingales, T.

N1 - Funding: CHEOPS is an ESA mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden, and the United Kingdom. The CHEOPS Consortium would like to gratefully acknowledge the support received by all the agencies, offices, universities, and industries involved. Their flexibility and willingness to explore new approaches were essential to the success of this mission. CHEOPS data analysed in this article will be made available in the CHEOPS mission archive ( https://cheops.unige.ch/archive_browser/ ). T.Wi. acknowledges support from the UKSA and the University of Warwick. This work has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grants 51NF40_182901 and 51NF40_205606. A.Br. was supported by the SNSA. S.G.S. acknowledge support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. A.Si. and C.Br. acknowledge support from the Swiss Space Office through the ESA PRODEX program. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). Y.Al. acknowledges support from the Swiss National Science Foundation (SNSF) under grant 200020_192038. N.C.Sa. acknowledges funding by the European Union (ERC, FIERCE, 101052347). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. V.V.G. is an F.R.S-FNRS Research Associate. R.Al., D.Ba., E.Pa., and I.Ri. acknowledge financial support from the Agencia Estatal de Investigaci\u00F3n of the Ministerio de Ciencia e Innovaci\u00F3n MCIN/AEI/10.13039/501100011033 and the ERDF \u201CA way of making Europe\u201D through projects PID2019-107061GB-C61, PID2019-107061GB-C66, PID2021-125627OB-C31, and PID2021-125627OB-C32, from the Centre of Excellence \u201CSevero Ochoa\u201D award to the Instituto de Astrof\u00EDsica de Canarias (CEX2019-000920-S), from the Centre of Excellence \u201CMar\u00EDa de Maeztu\u201D award to the Institut de Ci\u00E8ncies de l\u2019Espai (CEX2020-001058-M), and from the Generalitat de Catalunya/CERCA programme. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. L.Bo., V.Na., I.Pa., G.Pi., R.Ra., G.Sc., and T.Zi. acknowledge support from CHEOPS ASI-INAF agreement no. 2019-29-HH.0. 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.E.C. is funded by the Austrian Science Fund (FWF) Erwin Schroedinger Fellowship, program J4595-N. This project was supported by the CNES. The Belgian participation to CHEOPS has been supported by the Belgian Federal Science Policy Office (BELSPO) in the framework of the PRODEX Program, and by the University of Li\u00E8ge through an ARC grant for Concerted Research Actions financed by the Wallonia-Brussels Federation. L.D. is an F.R.S.-FNRS Postdoctoral Researcher. This work was supported by FCT \u2013 Funda\u00E7\u00E3o para a Ci\u00EAncia e a Tecnologia through national funds and by FEDER through COMPETE2020 through the research grants UIDB/04434/2020, UIDP/04434/2020, 2022.06962.PTDC. O.D.S.D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B.-O.D. acknowledges support from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number MB22.00046. This project has received funding from the European Research Council (ERC) under the European Union\u2019s Horizon 2020 research and innovation programme (project F OUR A CES . grant agreement no. 724427). It has also been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D.E. acknowledges financial support from the Swiss National Science Foundation for project 200021_200726. M.F. and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19, 174/18). A.J.M. acknowledges support from the Swedish National Space Agency (120/19C). D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 \u201CGaseousor rocky? Unveiling the nature of small worlds\u201D. M.G. is an F.R.S.-FNRS Senior Research Associate. M.N.G. is the ESA CHEOPS Project Scientist and Mission Representative, and as such also responsible for the Guest Observers (GO) Programme. M.N.G. does not relay proprietary information between the GO and Guaranteed Time Observation (GTO) Programmes, and does not decide on the definition and target selection of the GTO Programme. C.He. acknowledges support from the European Union H2020-MSCA-ITN-2019 under Grant Agreement no. 860470 (CHAMELEON). S.H. gratefully acknowledges CNES funding through the grant 837319. K.G.I. is the ESA CHEOPS Project Scientist and is responsible for the ESA CHEOPS Guest Observers Programme. She does not participate in, or contribute to, the definition of the Guaranteed Time Programme of the CHEOPS mission through which observations described in this paper have been taken, nor to any aspect of target selection for the programme. K.W.F.L. was supported by Deutsche Forschungsgemeinschaft grants RA714/14-1 within the DFG Schwerpunkt SPP 1992, Exploring the Diversity of Extrasolar Planets. This work was granted access to the HPC resources of MesoPSL financed by the Region Ile de France and the project Equip@Meso (reference ANR-10-EQPX-29-01) of the programme Investissements d\u2019Avenir supervised by the Agence Nationale pour la Recherche. P.M. acknowledges support from STFC research grant number ST/M001040/1. G.S. acknowledges support provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51519.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Gy.M.Sz. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a a PRODEX Experiment Agreement No. 4000137122, the Lend\u00FClet LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. N.A.W. acknowledges UKSA grant ST/R004838/1. R.L. acknowledges funding from University of La Laguna through the Margarita Salas Fellowship from the Spanish Ministry of Universities ref. UNI/551/2021-May 26, and under the EU Next Generation funds. This work has made use of data from the European Space Agency (ESA) mission Gaia ( https://www.cosmos.esa.int/gaia ), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium ). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This article is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos S\u00E1nchez operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This work is partly financed by the Spanish Ministry of Economics and Competitiveness through grants PGC2018-098153-B-C31. This work is partly supported by JSPS KAKENHI Grant Numbers JP17H04574, JP18H01265, and JP18H05439, Grant-in-Aid for JSPS Fellows Grant Number JP20J21872, JST PRESTO Grant Number JPMJPR1775, and a University Research Support Grant from the National Astronomical Observatory of Japan (NAOJ). This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE 1746045.

PY - 2024/2/1

Y1 - 2024/2/1

N2 - Context. 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-732b is an ultrashort-period planet (P = 0.76837931-0.00000042+0.0000039 days) with a radius Rb = 1.325-0.058+0.057R⊕, a mass Mb = 2.46 ± 0.19 M⊕, and thus a mean density ρb = 5.8-0.8+1.0 g cm-3, while the outer planet at P = 12.252284 ± 0.000013 days has Rc = 2.39-0.11+0.10R⊕, Mc = 8.04-0.48+0.50M⊕, and thus ρc = 3.24-0.43+0.55 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 logP = -0.065-0.013+0.024, 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 ρˆvalley / d log P = -0.02-0.04+0.12.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.

AB - Context. 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-732b is an ultrashort-period planet (P = 0.76837931-0.00000042+0.0000039 days) with a radius Rb = 1.325-0.058+0.057R⊕, a mass Mb = 2.46 ± 0.19 M⊕, and thus a mean density ρb = 5.8-0.8+1.0 g cm-3, while the outer planet at P = 12.252284 ± 0.000013 days has Rc = 2.39-0.11+0.10R⊕, Mc = 8.04-0.48+0.50M⊕, and thus ρc = 3.24-0.43+0.55 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 logP = -0.065-0.013+0.024, 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 ρˆvalley / d log P = -0.02-0.04+0.12.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.

KW - Planets and satellites: fundamental parameters

KW - Stars: fundamental parameters

KW - Techniques: photometric

KW - Techniques: radial velocities

U2 - 10.1051/0004-6361/202348180

DO - 10.1051/0004-6361/202348180

M3 - Article

AN - SCOPUS:85184519282

SN - 0004-6361

VL - 682

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A66

ER -

Characterising TOI-732 b and c: New insights into the M-dwarf radius and density valley

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Projects

AO2 - Professor Andrew Cameron: Project AO2 - Andrew Cameron

Astronomy at St Andrews 2018-2021: Astronomy at St Andrews 2018-2021

Support for the PLATO Development: Support for the PLATO Development Phase 2017-2022: Planet candidate ranking and validation

Datasets

TOI-732 TESS and CHEOPS detrended light curves

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