A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780
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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.
Cloutier , R , Eastman , J D , Rodriguez , J E , Astudillo-Defru , N , Bonfils , X , Mortier , A , Watson , C A , Stalport , M , Pinamonti , M , Lienhard , F , Harutyunyan , A , Damasso , M , Latham , D W , Collins , K A , Massey , R , Irwin , J , Winters , J G , Charbonneau , D , Ziegler , C , Matthews , E , Crossfield , I J M , Kreidberg , L , Quinn , S N , Ricker , G , Vanderspek , R , Seager , S , Winn , J , Jenkins , J M , Vezie , M , Udry , S , Twicken , J D , Tenenbaum , P , Sozzetti , A , Ségransan , D , Schlieder , J E , Sasselov , D , Santos , N C , Rice , K , Rackham , B V , Poretti , E , Piotto , G , Phillips , D , Pepe , F , Molinari , E , Mignon , L , Micela , G , Melo , C , de Medeiros , J R , Mayor , M , Matson , R A , Martinez Fiorenzano , A F , Mann , A W , Magazzú , A , Lovis , C , López-Morales , M , Lopez , E , Lissauer , J J , Lépine , S , Law , N , Kielkopf , J F , Johnson , J A , Jensen , E L N , Howell , S B , Gonzales , E , Ghedina , A , Forveille , T , Figueira , P , Dumusque , X , Dressing , C D , Doyon , R , Díaz , R F , Fabrizio , L D , Delfosse , X , Cosentino , R , Conti , D M , Collins , K I , Cameron , A C , Ciardi , D , Caldwell , D A , Burke , C , Buchhave , L , Briceño , C , Boyd , P , Bouchy , F , Beichman , C , Artigau , É & Almenara , J M 2020 , ' A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780 ' , Astronomical Journal , vol. 160 , no. 1 , 3 . https://doi.org/10.3847/1538-3881/ab91c2
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DescriptionFunding: N.A.D. acknowledges support from FONDECYT 3180063.A.M. acknowledges support from the senior Kavli InstituteFellowships.J.G.W. is supported by a grant from the John Templeton Foundation. .C.Z. is supported by a Dunlap Fellowship at the Dunlap Institute for Astronomy & Astrophysics, funded through an endowment established by the Dunlap family and the University of Toronto. I.J.M.C. acknowledges support from the NSF through grant AST-1824644 and NASA through Caltech/JPL grant RSA-1610091. F.L. gratefully acknowledges a scholarship from the Fondation Zd̆nek et Michaela Bakala. M.S. thanks the Swiss National Science Foundation (SNSF) and Geneva University for their continuous support of our exoplanet researches. This work has been in particular carried out in the frame of the National Center for Competence in Research “PlanetS” supported by SNSF.C.A.W. acknowledges support from Science and Technology Facilities Council grant ST/P000312/1. N.C.S. acknowledges 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. M.Pi. gratefully acknowledges support from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement No. 313014 (ETAEARTH). J.R.M. acknowledges support by the CAPES, CNPq, and FAPERN Brazilian agencies.
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