A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780

Ryan Cloutier, Jason D. Eastman, Joseph E. Rodriguez, Nicola Astudillo-Defru, Xavier Bonfils, Annelies Mortier, Christopher A. Watson, Manu Stalport, Matteo Pinamonti, Florian Lienhard, Avet Harutyunyan, Mario Damasso, David W. Latham, Karen A. Collins, Robert Massey, Jonathan Irwin, Jennifer G. Winters, David Charbonneau, Carl Ziegler, Elisabeth MatthewsIan J. M. Crossfield, Laura Kreidberg, Samuel N. Quinn, George Ricker, Roland Vanderspek, Sara Seager, Joshua Winn, Jon M. Jenkins, Michael Vezie, Stéphane Udry, Joseph D. Twicken, Peter Tenenbaum, Alessandro Sozzetti, Damien Ségransan, Joshua E. Schlieder, Dimitar Sasselov, Nuno C. Santos, Ken Rice, Benjamin V. Rackham, Ennio Poretti, Giampaolo Piotto, David Phillips, Francesco Pepe, Emilio Molinari, Lucile Mignon, Giuseppina Micela, Claudio Melo, José R. de Medeiros, Michel Mayor, Rachel A. Matson, Aldo F. Martinez Fiorenzano, Andrew W. Mann, Antonio Magazzú, Christophe Lovis, Mercedes López-Morales, Eric Lopez, Jack J. Lissauer, Sébastien Lépine, Nicholas Law, John F. Kielkopf, John A. Johnson, Eric L. N. Jensen, Steve B. Howell, Erica Gonzales, Adriano Ghedina, Thierry Forveille, Pedro Figueira, Xavier Dumusque, Courtney D. Dressing, René Doyon, Rodrigo F. Díaz, Luca Di Fabrizio, Xavier Delfosse, Rosario Cosentino, Dennis M. Conti, Kevin I. Collins, Andrew Collier Cameron, David Ciardi, Douglas A. Caldwell, Christopher Burke, Lars Buchhave, César Briceño, Patricia Boyd, François Bouchy, Charles Beichman, Étienne Artigau, Jose M. Almenara

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62 Citations (Scopus)


We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT 3780 (TIC 36724087, TOI-732, V = 13.07, Ks =8.204, Rs = 0.374 R⊙, Ms = 0.401 M⊙, d = 22 pc). The two planet candidates are identified in a single Transiting Exoplanet Survey Satellite sector and validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of Pb = 0.77, Pc = 12.25 days and sizes rp,b = 1.33 ± 0.07, rp,c = 2.30 ±0.16 R⊕, the two planets span the radius valley in period-radius space around low-mass stars, thus making the system a laboratory to test competing theories of the emergence of the radius valley in that stellar mass regime. By combining 63 precise radial velocity measurements from the High Accuracy Radial velocity Planet Searcher (HARPS) and HARPS-N, we measure planet masses of mp,b = 2.62-0.46+0.48 and mp,c = 8.6-1.3+1.6 M⊕, which indicates that LTT 3780b has a bulk composition consistent with being Earth-like, while LTT 3780c likely hosts an extended H/He envelope. We show that the recovered planetary masses are consistent with predictions from both photoevaporation and core-powered mass-loss models. The brightness and small size of LTT 3780, along with the measured planetary parameters, render LTT 3780b and c as accessible targets for atmospheric characterization of planets within the same planetary system and spanning the radius valley.
Original languageEnglish
Article number3
Number of pages21
JournalAstronomical Journal
Issue number1
Early online date4 Jun 2020
Publication statusPublished - Jul 2020


  • Radial velocity
  • M dwarf stars
  • Exoplanet systems
  • Transit photometry


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