A pair of TESS planets spanning the radius valley around the nearby mid-M dwarf LTT 3780
Creators: name: Cloutier, Ryan
name: Eastman, Jason D.
name: Rodriguez, Joseph E.
name: Astudillo-Defru, Nicola
name: Bonfils, Xavier
name: Mortier, Annelies
name: Watson, Christopher A.
name: Stalport, Manu
name: Pinamonti, Matteo
name: Lienhard, Florian
name: Harutyunyan, Avet
name: Damasso, Mario
name: Latham, David W.
name: Collins, Karen A.
name: Massey, Robert
name: Irwin, Jonathan
name: Winters, Jennifer G.
name: Charbonneau, David
name: Ziegler, Carl
name: Matthews, Elisabeth
name: Crossfield, Ian J. M.
name: Kreidberg, Laura
name: Quinn, Samuel N.
name: Ricker, George
name: Vanderspek, Roland
name: Seager, Sara
name: Winn, Joshua
name: Jenkins, Jon M.
name: Vezie, Michael
name: Udry, Stéphane
name: Twicken, Joseph D.
name: Tenenbaum, Peter
name: Sozzetti, Alessandro
name: Ségransan, Damien
name: Schlieder, Joshua E.
name: Sasselov, Dimitar
name: Santos, Nuno C.
name: Rice, Ken
name: Rackham, Benjamin V.
name: Poretti, Ennio
name: Piotto, Giampaolo
name: Phillips, David
name: Pepe, Francesco
name: Molinari, Emilio
name: Mignon, Lucile
name: Micela, Giuseppina
name: Melo, Claudio
name: de Medeiros, José R.
name: Mayor, Michel
name: Matson, Rachel
name: Fiorenzano, Aldo F. Martinez
name: Mann, Andrew W.
name: Magazzú, Antonio
name: Lovis, Christophe
name: López-Morales, Mercedes
name: Lopez, Eric
name: Lissauer, Jack J.
name: Lépine, Sébastien
name: Law, Nicholas
name: Kielkopf, John F.
name: Johnson, John A.
name: Jensen, Eric L. N.
name: Howell, Steve B.
name: Gonzales, Erica
name: Ghedina, Adriano
name: Forveille, Thierry
name: Figueira, Pedro
name: Dumusque, Xavier
name: Dressing, Courtney D.
name: Doyon, René
name: Díaz, Rodrigo F.
name: Di Fabrizio, Luca
name: Delfosse, Xavier
name: Cosentino, Rosario
name: Conti, Dennis M.
name: Collins, Kevin I.
name: Cameron, Andrew Collier
name: Ciardi, David
name: Caldwell, Douglas A.
name: Burke, Christopher
name: Buchhave, Lars
name: Briceño, César
name: Boyd, Patricia
name: Bouchy, François
name: Beichman, Charles
name: Artigau, Étienne
name: Almenara, Jose M.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present the confirmation of two new planets transiting the nearby mid-M dwarf LTT 3780 (TIC 36724087, TOI-732, $V=13.07$, $K_s=8.204$, $R_s$=0.374 R$_{\odot}$, $M_s$=0.401 M$_{\odot}$, d=22 pc). The two planet candidates are identified in a single TESS sector and are validated with reconnaissance spectroscopy, ground-based photometric follow-up, and high-resolution imaging. With measured orbital periods of $P_b=0.77$ days, $P_c=12.25$ days and sizes $r_{p,b}=1.33\pm 0.07$ R$_{\oplus}$, $r_{p,c}=2.30\pm 0.16$ R$_{\oplus}$, 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 HARPS and HARPS-N, we measure planet masses of $m_{p,b}=2.62^{+0.48}_{-0.46}$ M$_{\oplus}$ and $m_{p,c}=8.6^{+1.6}_{-1.3}$ M$_{\oplus}$, 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 from 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.
description: Accepted to AJ. 8 figures, 6 tables. CSV file of the RV measurements (i.e. Table 2) are included in the source code