A Second Planet Transiting LTT 1445A and a Determination of the Masses   of Both Worlds

J.G. Winters (1); R. Cloutier (1,53); A.A. Medina (1); J.M. Irwin (1),; D. Charbonneau (1); N. Astudillo-Defru (2); X. Bonfils (3); A.W. Howard (4),; H. Isaacson (5,6); J.L. Bean (7); A. Seifahrt (7); J.K. Teske (8); J.D.; Eastman (1); J.D. Twicken (9,10); K.A. Collins (1); E.L.N. Jensen (11); S.N.; Quinn (1); M.J. Payne (1); M.H. Kristiansen (12,13); A. Spencer (14); A.; Vanderburg (15); M. Zechmeister (16); L.M. Weiss (17); S.X. Wang (18); G.; Wang (19,20); S. Udry (21); I.A. Terentev (22); J. Sturmer (23); G.; Stefansson (24,56); A. Shporer (15); S. Shectman (25); R. Sefako (26); H.M.; Schwengeler (22); R.P. Schwarz (27); N. Scarsdale (28); R.A. Rubenzahl; (4,54); A. Roy (29,30); L.J. Rosenthal (4); P. Robertson (31); E.A. Petigura; (32); F. Pepe (21); M. Omohundro (22); J.M.A. Murphy (28,54); F. Murgas; (33,34); T. Movcnik (35); B.T. Montet (36); R. Mennickent (37); A.W. Mayo; (5,38); B. Massey (39); J. Lubin (31); C. Lovis (21); P. Lewin (40); D.; Kasper (7); S.R. Kane (41); J.M. Jenkins (10); D. Huber (42); K. Horne (43),; M.L. Hill (41); P. Gorrini (16); S. Giacalone (5); B. Fulton (44); T.; Forveille (3); P. Figueira (45,46); T. Fetherolf (41,57); C. Dressing (5),; R.F. Diaz (47); X. Delfosse (3); P.A. Dalba (28,41,55); F. Dai (4); C.C.; Cortes (37,48); I.J.M. Crossfield (49); J.D. Crane (25); D.M. Conti (50),; K.I. Collins (51); A. Chontos (42,54); R.P. Butler (8); P. Brown (52); M.; Brady (7); A. Behmard (4,54); C. Beard (31); N.M. Batalha (28); J.-M.; Almenara (3) ((1) Center for Astrophysics | Harvard & Smithsonian; (2); Universidad Catolica de la Santisima Concepcion; (3) Universite Grenoble; Alpes; (4) California Institute of Technology; (5) University of California; Berkeley; (6) University of Southern Queensland; (7) University of Chicago,; (8) Earth; Planets Laboratory of the Carnegie Institution for Science; (9); SETI Institute; (10) NASA Ames Research Center; (11) Swarthmore College; (12); Brorfelde Observatory; (13) Technical University of Denmark; (14) Western; Connecticut State University; (15) Massachusetts Institute of Technology,; (16) Georg-August-Universitaet; (17) University of Notre Dame; (18) Tsinghua; University; (19) Tsinghua International School; (20) Stanford Online High; School; (21) Observatoire de Geneve; (22) Citizen Scientist; (23); Universitaet Heidelberg; (24) Princeton University; (25) The Observatories of; the Carnegie Institution for Science; (26) South African Astronomical; Observatory; (27) Patashnick Voorheesville Observatory; (28) University of; California Santa Cruz; (29) Space Telescope Science Institute; (30) Johns; Hopkins University; (31) University of California Irvine; (32) University of; California Los Angeles; (33) Instituo de Astrofisica da Canarias; (34); Universidad de La Laguna; (35) Gemini Observatory/NSF's NOIRLab; (36); University of New South Wales; (37) Universidad de Concepcion; (38); University of Copenhagen; (39) Villa '39 Observatory; (40) The Maury Lewin; Astronomical Observatory; (41) University of California Riverside; (42); University of Hawai`i; (43) University of St. Andrews; (44) NASA Exoplanet; Science Institute/Caltech-IPAC; (45) European Southern Observatory; (46); Universidade do Porto; (47) International Center for Advanced Studies (ICAS); and ICIFI (CONICET); (48) Universidad del Bio-Bio; (49) University of Kansas,; (50) American Association of Variable Star Observers; (51) George Mason; University; (52) Vanderbilt University; (53) Banting Fellow; (54) NSF; Graduate Research Fellow; (55) NSF Astronomy; Astrophysics Postdoctoral; Fellow; (56) Henry Norris Russell Fellow; (57) UC Chancellor's Fellow)

arXiv:2107.14737·astro-ph.EP·March 30, 2022

A Second Planet Transiting LTT 1445A and a Determination of the Masses of Both Worlds

J.G. Winters (1), R. Cloutier (1,53), A.A. Medina (1), J.M. Irwin (1),, D. Charbonneau (1), N. Astudillo-Defru (2), X. Bonfils (3), A.W. Howard (4),, H. Isaacson (5,6), J.L. Bean (7), A. Seifahrt (7), J.K. Teske (8), J.D., Eastman (1), J.D. Twicken (9,10), K.A. Collins (1)

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TL;DR

This paper reports the discovery of a second transiting planet in the LTT 1445A system, along with precise mass and radius measurements for both planets, using TESS data and multiple spectrographs, revealing insights into the system's stellar evolution.

Contribution

The study presents the first detection of a second planet transiting LTT 1445A and provides detailed mass and radius measurements, enhancing understanding of this nearby M-dwarf system.

Findings

01

Discovered a second planet with a 3.1-day orbit around LTT 1445A.

02

Measured the masses and radii of both planets, indicating Earth-like composition.

03

Analyzed stellar rotation periods, revealing different evolutionary stages of the system's stars.

Abstract

LTT 1445 is a hierarchical triple M-dwarf star system located at a distance of 6.86 parsecs. The primary star LTT 1445A (0.257 M_Sun) is known to host the transiting planet LTT 1445Ab with an orbital period of 5.4 days, making it the second closest known transiting exoplanet system, and the closest one for which the host is an M dwarf. Using TESS data, we present the discovery of a second planet in the LTT 1445 system, with an orbital period of 3.1 days. We combine radial velocity measurements obtained from the five spectrographs ESPRESSO, HARPS, HIRES, MAROON-X, and PFS to establish that the new world also orbits LTT 1445A. We determine the mass and radius of LTT 1445Ab to be 2.87+/-0.25 M_Earth and 1.304^{+0.067}_{-0.060} R_Earth, consistent with an Earth-like composition. For the newly discovered LTT 1445Ac, we measure a mass of 1.54^{+0.20}_{-0.19} M_Earth and a minimum radius of…

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