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., Estrada, B. Campos, 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., Barragan, 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., Diaz, R. F., Doyon, R., Esposito, M., Furesz, 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., Suarez Mascareno, A., Subjak, J., Twicken, J. D., Udry, S., Vanderspek, R. and Zapatero Osorio, M. R. (2021). Masses and compositions of three small planets orbiting the nearby M dwarf L231-32 (TOI-270) and the M dwarf radius valley. Mon. Not. Roy. Astron. Soc., 507 (2). S. 2154 - 2174. OXFORD: OXFORD UNIV PRESS. ISSN 1365-2966

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Abstract

We report on precise Doppler measurements of L231-32 (TOI-270), a nearby M dwarf (d = 22pc, M-star = 0.39 M-circle dot, R-star = 0.38 R-circle dot), 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-circle plus, 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.

Item Type: Journal Article
Creators:
CreatorsEmailORCIDORCID Put Code
Van Eylen, V.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Astudillo-Defru, N.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bonfils, X.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Livingston, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Hirano, T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Luque, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lam, K. W. F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Justesen, A. B.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Winn, J. N.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Gandolfi, D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Nowak, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Palle, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Albrecht, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Dai, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Estrada, B. CamposUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Owen, J. E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Foreman-Mackey, D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Fridlund, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Korth, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Mathur, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Forveille, T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Mikal-Evans, T.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Osborne, H. L. M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Ho, C. S. K.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Almenara, J. M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Artigau, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Barragan, O.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Barros, S. C. C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Bouchy, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Cabrera, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Caldwell, D. A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Charbonneau, D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Chaturvedi, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Cochran, W. D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Csizmadia, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Damasso, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Delfosse, X.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
De Medeiros, J. R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Diaz, R. F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Doyon, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Esposito, M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Furesz, G.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Figueira, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Georgieva, IUNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Goffo, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Grziwa, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Guenther, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Hatzes, A. P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Jenkins, J. M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Kabath, P.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Knudstrup, E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Latham, D. W.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lavie, B.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Lovis, C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Mennickent, R. E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Mullally, S. E.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Murgas, F.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Narita, N.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Pepe, F. A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Persson, C. M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Redfield, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Ricker, G. R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Santos, N. C.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Seager, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Serrano, L. M.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Smith, A. M. S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Suarez Mascareno, A.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Subjak, J.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Twicken, J. D.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Udry, S.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Vanderspek, R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
Zapatero Osorio, M. R.UNSPECIFIEDUNSPECIFIEDUNSPECIFIED
URN: urn:nbn:de:hbz:38-607894
DOI: 10.1093/mnras/stab2143
Journal or Publication Title: Mon. Not. Roy. Astron. Soc.
Volume: 507
Number: 2
Page Range: S. 2154 - 2174
Date: 2021
Publisher: OXFORD UNIV PRESS
Place of Publication: OXFORD
ISSN: 1365-2966
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
KeywordsLanguage
SUPER-EARTH; SURFACE ROTATION; ERROR-CORRECTION; KEPLER; EXOPLANET; STELLAR; STAR; VELOCITY; SEARCH; EVAPORATIONMultiple languages
Astronomy & AstrophysicsMultiple languages
URI: http://kups.ub.uni-koeln.de/id/eprint/60789

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