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A planetary system with two transiting mini-Neptunes near the radius valley transition around the bright M dwarf TOI-776

We report the discovery and characterization of two transiting planets around the bright M1 V star LP 961-53 (TOI-776, J = 8.5 mag, M = 0.54 ± 0.03 M⊙) detected during Sector 10 observations of the Transiting Exoplanet Survey Satellite (TESS). Combining the TESS photometry with HARPS radial velociti...

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Main Authors: Luque, Rafael (Author) , Serrano, L. M. (Author) , Molaverdikhani, Karan (Author) , Nixon, M. C. (Author) , Livingston, J. H. (Author) , Guenther, E. W. (Author) , Pallé, E. (Author) , Madhusudhan, N. (Author) , Nowak, G. (Author) , Korth, J. (Author) , Cochran, W. D. (Author) , Hirano, T. (Author) , Chaturvedi, P. (Author) , Goffo, E. (Author) , Albrecht, S. (Author) , Barragán, O. (Author) , Briceño, C. (Author) , Cabrera, J. (Author) , Charbonneau, D. (Author) , Cloutier, R. (Author) , Collins, K. A. (Author) , Collins, K. I. (Author) , Colón, K. D. (Author) , Crossfield, I. J. M. (Author) , Csizmadia, Sz (Author) , Dai, F. (Author) , Deeg, H. J. (Author) , Esposito, M. (Author) , Fridlund, M. (Author) , Gandolfi, D. (Author) , Georgieva, I. (Author) , Glidden, A. (Author) , Goeke, R. F. (Author) , Grziwa, S. (Author) , Hatzes, A. P. (Author) , Henze, C. E. (Author) , Howell, S. B. (Author) , Irwin, J. (Author) , Jenkins, J. M. (Author) , Jensen, E. L. N. (Author) , Kábath, P. (Author) , Kidwell, R. C. (Author) , Kielkopf, J. F. (Author) , Knudstrup, E. (Author) , Lam, K. W. F. (Author) , Latham, D. W. (Author) , Lissauer, J. J. (Author) , Mann, A. W. (Author) , Matthews, E. C. (Author) , Mireles, I. (Author) , Narita, N. (Author) , Paegert, M. (Author) , Persson, C. M. (Author) , Redfield, S. (Author) , Ricker, G. R. (Author) , Rodler, F. (Author) , Schlieder, J. E. (Author) , Scott, N. J. (Author) , Seager, S. (Author) , Šubjak, J. (Author) , Tan, T. G. (Author) , Ting, E. B. (Author) , Vanderspek, R. (Author) , Eylen, V. Van (Author) , Winn, J. N. (Author) , Ziegler, C. (Author)
Format: Article (Journal)
Language:English
Published: 05 January 2021
In: Astronomy and astrophysics
Year: 2021, Volume: 645, Pages: 1-24
ISSN:1432-0746
DOI:10.1051/0004-6361/202039455
Online Access:Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1051/0004-6361/202039455
Verlag, lizenzpflichtig, Volltext: https://www.aanda.org/articles/aa/abs/2021/01/aa39455-20/aa39455-20.html
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Author Notes:R. Luque, L.M. Serrano, K. Molaverdikhani, M.C. Nixon, J.H. Livingston, E.W. Guenther, E. Pallé, N. Madhusudhan, G. Nowak, J. Korth, W.D. Cochran, T. Hirano, P. Chaturvedi, E. Goffo, S. Albrecht, O. Barragán, C. Briceño, J. Cabrera, D. Charbonneau, R. Cloutier, K.A. Collins, K.I. Collins, K.D. Colón, I.J.M. Crossfield, Sz. Csizmadia, F. Dai, H.J. Deeg, M. Esposito, M. Fridlund, D. Gandolfi, I. Georgieva, A. Glidden, R.F. Goeke, S. Grziwa, A.P. Hatzes, C.E. Henze, S.B. Howell, J. Irwin, J.M. Jenkins, E.L.N. Jensen, P. Kábath, R.C. Kidwell, J.F. Kielkopf, E. Knudstrup, K.W.F. Lam, D.W. Latham, J.J. Lissauer, A.W. Mann, E.C. Matthews, I. Mireles, N. Narita, M. Paegert, C.M. Persson, S. Redfield, G.R. Ricker, F. Rodler, J.E. Schlieder, N.J. Scott, S. Seager, J. Šubjak, T.G. Tan, E.B. Ting, R. Vanderspek, V. Van Eylen, J.N. Winn, and C. Ziegler
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Summary:We report the discovery and characterization of two transiting planets around the bright M1 V star LP 961-53 (TOI-776, J = 8.5 mag, M = 0.54 ± 0.03 M⊙) detected during Sector 10 observations of the Transiting Exoplanet Survey Satellite (TESS). Combining the TESS photometry with HARPS radial velocities, as well as ground-based follow-up transit observations from the MEarth and LCOGT telescopes, for the inner planet, TOI-776 b, we measured a period of Pb = 8.25 d, a radius of Rb = 1.85 ± 0.13 R⊕, and a mass of Mb = 4.0 ± 0.9 M⊕; and for the outer planet, TOI-776 c, a period of Pc = 15.66 d, a radius of Rc = 2.02 ± 0.14 R⊕, and a mass of Mc = 5.3 ± 1.8 M⊕. The Doppler data shows one additional signal, with a period of ~34 d, associated with the rotational period of the star. The analysis of fifteen years of ground-based photometric monitoring data and the inspection of different spectral line indicators confirm this assumption. The bulk densities of TOI-776 b and c allow for a wide range of possible interior and atmospheric compositions. However, both planets have retained a significant atmosphere, with slightly different envelope mass fractions. Thanks to their location near the radius gap for M dwarfs, we can start to explore the mechanism(s) responsible for the radius valley emergence around low-mass stars as compared to solar-like stars. While a larger sample of well-characterized planets in this parameter space is still needed to draw firm conclusions, we tentatively estimate that the stellar mass below which thermally-driven mass loss is no longer the main formation pathway for sculpting the radius valley is between 0.63 and 0.54 M⊙. Due to the brightness of the star, the TOI-776 system is also an excellent target for the James Webb Space Telescope, providing a remarkable laboratory in which to break the degeneracy in planetary interior models and to test formation and evolution theories of small planets around low-mass stars.
Item Description:Gesehen am 07.05.2022
Physical Description:Online Resource
ISSN:1432-0746
DOI:10.1051/0004-6361/202039455

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