Masses and compositions of three small planets orbiting the nearby M dwarf L231-32 (TOI-270) and the M dwarf radius valley
- Creators
- Van Eylen, V.
- Astudillo-Defru, N.
- Bonfils, X.
- Livingston, J.
- Hirano, T.
- Luque, R.
- Lam, K. W. F.
- Justesen, A. B.
- Winn, J. N.
- Gandolfi, D.
- Nowak, G.
- Palle, E.
- Albrecht, S.
- Dai, F.
- Campos Estrada, B.
- Owen, J. E.
- Foreman-Mackey, D.
- Fridlund, M.
- Korth, J.
- Mathur, S.
- Forveille, T.
- Mikal-Evans, T.
- Osborne, H. L. M.
- Ho, C. S. K.
- Almenara, J. M.
- Artigau, E.
- Barragán, O.
- Barros, S. C. C.
- Bouchy, F.
- Cabrera, J.
- Caldwell, D. A.
- Charbonneau, D.
- Chaturvedi, P.
- Cochran, W. D.
- Csizmadia, S.
- Damasso, M.
- Delfosse, X.
- de Medeiros, J. R.
- Díaz, R. F.
- Doyon, R.
- Esposito, M.
- Fűrész, G.
- Figueira, P.
- Georgieva, I.
- Goffo, E.
- Grziwa, S.
- Guenther, E.
- Hatzes, A. P.
- Jenkins, J. M.
- Kabath, P.
- Knudstrup, E.
- Latham, D. W.
- Lavie, B.
- Lovis, C.
- Mennickent, R. E.
- Mullally, S. E.
- Murgas, F.
- Narita, N.
- Pepe, F. A.
- Persson, C. M.
- Redfield, S.
- Ricker, G. R.
- Santos, N. C.
- Seager, S.
- Serrano, L. M.
- Smith, A. M. S.
- Suárez Mascareño, A.
- Subjak, J.
- Twicken, J. D.
- Udry, S.
- Vanderspek, R.
- Zapatero Osorio, M. R.
Abstract
We report on precise Doppler measurements of L231-32 (TOI-270), a nearby M dwarf (d = 22 pc, M⋆ = 0.39 M_⊙, R⋆ = 0.38 R_⊙), which hosts three transiting planets that were recently discovered using data from the Transiting Exoplanet Survey Satellite (TESS). The three planets are 1.2, 2.4, and 2.1 times the size of Earth and have orbital periods of 3.4, 5.7, and 11.4 d. We obtained 29 high-resolution optical spectra with the newly commissioned Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) and 58 spectra using the High Accuracy Radial velocity Planet Searcher (HARPS). From these observations, we find the masses of the planets to be 1.58 ± 0.26, 6.15 ± 0.37, and 4.78 ± 0.43 M_⊕, respectively. The combination of radius and mass measurements suggests that the innermost planet has a rocky composition similar to that of Earth, while the outer two planets have lower densities. Thus, the inner planet and the outer planets are on opposite sides of the 'radius valley' – a region in the radius-period diagram with relatively few members – which has been interpreted as a consequence of atmospheric photoevaporation. We place these findings into the context of other small close-in planets orbiting M dwarf stars, and use support vector machines to determine the location and slope of the M dwarf (T_(eff) < 4000 K) radius valley as a function of orbital period. We compare the location of the M dwarf radius valley to the radius valley observed for FGK stars, and find that its location is a good match to photoevaporation and core-powered mass-loss models. Finally, we show that planets below the M dwarf radius valley have compositions consistent with stripped rocky cores, whereas most planets above have a lower density consistent with the presence of a H-He atmosphere.
Additional Information
© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. Accepted 2021 July 21. Received 2021 July 20; in original form 2020 December 10. Published: 24 August 2021. We are grateful to Megan Bedell for discussions about the extraction and precision of ESPRESSO radial velocity observations and Laura Kreidberg for discussions about HST observations of this system. Part of this work is done under the framework of the KESPRINT collaboration (http://kesprint.science). KESPRINT is an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions. Based on observations made with ESPRESSO on the Very Large Telescope, ESO observing programs 0102.C-0456, 1102.C-0744, and 1102.C-0958 and with HARPS at the ESO 3.6m telescope (program 1102.C-0339). Based on data from the TESS satellite. Funding for the TESS mission is provided by NASA's Science Mission directorate. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website and the NASA Exoplanet Archive, which are operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. 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 research made use of EXOPLANET (Foreman-Mackey et al. 2019) and its dependencies (Astropy Collaboration 2013, 2018; Kipping 2013; Salvatier et al. 2016; Theano Development Team 2016; Foreman-Mackey et al. 2019; Luger et al. 2019). N.A.-D. acknowledges the support of FONDECYT project 3180063. B.C.E received support from J.E.O's Royal Society 2020 Enhancement Award. J.E.O. is supported by a Royal Society University Research Fellowship. This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (PEVAP, Grant agreement No. 853022). S.A and A.B.J. acknowledge support from the Danish Council for Independent Research, through a DFF Sapere Aude Starting Grant no. 4181-00487B. M.F, I.G., and C.M.P. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19 and 174/18). This work is supported by JSPS KAKENHI Grant Number 19K14783. This work was supported by FCT – Fundação para a Ciência e a Tecnologia through national funds and by FEDER through COMPETE2020 – Programa Operacional Competitividade e Internacionalização by these grants: UID/FIS/04434/2019; UIDB/04434/2020; UIDP/04434/2020; PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113; PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953. P.K. and J.S. acknowledge Ministry of Education, Youth and Sports, Czech Republic, the grant INTER-TRANSFER number LTT20015. SM acknowledges support from the Spanish Ministry of Science and Innovation with the Ramon y Cajal fellowship number RYC-2015-17697 and from the grant number PID2019-107187GB-I00. J.R.M. acknowledges continuous grants from CNPq, CAPES, and FAPERN brazilian agencies. This work is partly supported by JSPS KAKENHI Grant Numbers JP18H01265 and JP18H05439, and JST PRESTO Grant Number JPMJPR1775. This work is partly financed by the Spanish Ministry of Economics and Competitiveness (MINECO) through project PGC2018-098153-B-C31. X.B., X.D., and T.F. acknowledge support from the French National Research Agency in the framework of the Investissements d'Avenir program (ANR- 15-IDEX-02), through the funding of the 'Origin of Life' project of the Univ. Grenoble-Alpes. M.E. acknowledges the support of the DFG priority program SPP 1992 'Exploring the Diversity of Extrasolar Planets' (HA 3279/12-1). This work is made possible by a grant from the John Templeton Foundation. The opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation. A.S.M. acknowledges financial support from the Spanish Ministry of Science, Innovation and Universities (MICIU) under the 2019 Juan de la Cierva and AYA2017-86389-P programmes. M.D. acknowledges financial support from Progetto Premiale 2015 FRONTIERA (OB.FU. 1.05.06.11) funding scheme of the Italian Ministry of Education, University, and Research. S.C.C.B. acknowledges support from Fundação para a Ciência e a Tecnologia (FCT) through Investigador FCT contract IF/01312/2014/CP1215/CT0004 and national funds (PTDC/FIS-AST/28953/2017) and by FEDER – Fundo Europeu de Desenvolvimento Regional through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI-01-0145-FEDER-028953) and through national funds (PIDDAC) by the grant UID/FIS/04434/2019. K.W.F.L. and Sz.Cs. acknowledge support by DFG grant RA714/14-1 within the DFG Schwerpunkt SPP 1992, Exploring the Diversity of Extrasolar Planets. Data Availability: This paper includes raw data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST, https://archive.stsci.edu/tess). Observations made with ESPRESSO on the Very Large Telescope and with HARPS at the ESO 3.6m telescope (programs 0102.C-0456, 1102.C-0744, 1102.C-0958, and 1102.C-0339) are publicly available at the ESO archive (http://archive.eso.org/). All processed data underlying this article are available in the article and in its online supplementary material. The code underlying EVAPMASS analysis for planets c & d's minimum predicted mass from the photoevaporation model are available at https://github.com/jo276/EvapMassTOI270.Attached Files
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Accepted Version - 2101.01593.pdf
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Additional details
- Eprint ID
- 111777
- Resolver ID
- CaltechAUTHORS:20211105-215008827
- NASA
- Gaia Multilateral Agreement
- 3180063
- Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT)
- Royal Society
- 853022
- European Research Council (ERC)
- 4181-00487B
- Danish Council for Independent Research
- DNR 65/19
- Swedish National Space Agency
- DNR 174/18
- Swedish National Space Agency
- 19K14783
- Japan Society for the Promotion of Science (JSPS)
- UID/FIS/04434/2019
- Fundação para a Ciência e a Tecnologia (FCT)
- UIDB/04434/2020
- Fundação para a Ciência e a Tecnologia (FCT)
- UIDP/04434/2020
- Fundação para a Ciência e a Tecnologia (FCT)
- PTDC/FIS-AST/32113/2017
- Fundação para a Ciência e a Tecnologia (FCT)
- POCI-01-0145-FEDER-032113
- Fundação para a Ciência e a Tecnologia (FCT)
- PTDC/FIS-AST/28953/2017
- Fundação para a Ciência e a Tecnologia (FCT)
- POCI-01-0145-FEDER-028953
- Fundação para a Ciência e a Tecnologia (FCT)
- Ministry of Education, Youth and Sports (Czech Republic)
- LTT20015
- INTER-TRANSFER
- RYC-2015-17697
- Ramón y Cajal Programme
- PID2019-107187GB-I00
- Ministerio de Ciencia e Innovación (MCINN)
- Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
- Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
- Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ)
- JP18H01265
- Japan Society for the Promotion of Science (JSPS)
- JP18H05439
- Japan Society for the Promotion of Science (JSPS)
- JPMJPR1775
- Japan Science and Technology Agency
- PGC2018-098153-B-C31
- Ministerio de Economía, Industria y Competitividad (MINECO)
- ANR-15-IDEX-02
- Agence Nationale pour la Recherche (ANR)
- University of Grenoble
- HA 3279/12-1
- Deutsche Forschungsgemeinschaft (DFG)
- John Templeton Foundation
- AYA2017-86389-P
- Ministerio de Ciencia, Innovación y Universidades (MCIU)
- OB.FU. 1.05.06.11
- Progetto Premiale 2015 FRONTIERA
- Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR)
- IF/01312/2014/CP1215/CT0004
- Fundação para a Ciência e a Tecnologia (FCT)
- PTDC/FIS-AST/28953/2017
- Fundação para a Ciência e a Tecnologia (FCT)
- Fondo Europeo de Desarrollo Regional (FEDER)
- POCI-01-0145-FEDER-028953
- Fundação para a Ciência e a Tecnologia (FCT)
- UID/FIS/04434/2019
- Fundação para a Ciência e a Tecnologia (FCT)
- RA714/14-1
- Deutsche Forschungsgemeinschaft (DFG)
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2021-11-12Created from EPrint's datestamp field
- Updated
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2021-11-12Created from EPrint's last_modified field