Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M-dwarf System at 6.9 pc
Date
2019-10Author
Winters, Jennifer G.
Medina, Amber A.
Irwin, Jonathan M.
Charbonneau, David
Astudillo Defru, Nicola
Horch, Elliott P.
Eastman, Jason D.
Vrijmoet, Eliot Halley
Henry, Todd J.
Diamond-Lowe, Hannah
Winston, Elaine
Barclay, Thomas
Bonfils, Xavier
Ricker, George R.
Vanderspek, Roland
Latham, David W.
Seager, Sara
Winn, Joshua N.
Jenkins, Jon M.
Udry, Stéphane
Twicken, Joseph D.
Teske, Johanna K.
Tenenbaum, Peter
Pepe, Francesco
Murgas, Felipe
Muirhead, Philip S.
Mink, Jessica
Lovis, Christophe
Levine, Alan M.
Lépine, Sébastien
Jao, Wei-Chun
Henze1, Cristopher E.
Furész, Gábor
Forveille, Thierry
Figueira, Pedro
Esquerdo, Gilbert A.
Dressing, Courtney D.
Díaz, Rodrigo F.
Delfosse, Xavier
Burke, Christopher J.
Bouchy, François
Berlind, Perry
Almenara, José Manuel
Publisher
The Astronomical JournalDescription
Metadata
Show full item recordAbstract
We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of
6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the
primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical
configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing
Operations Center data validation report to determine that the planet transits the primary star in the system. The
planet has a radius of -
+ 1.38 0.12
0.13 RÅ, an orbital period of -
+ 5.35882 0.00031
0.00030 days, and an equilibrium temperature of
-
+ 433 27
28 K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper
mass limit of 8.4 MÅ on the planet. LTT 1445Ab provides one of the best opportunities to date for the
spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host
stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar
or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount
of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric
orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this
system hints that the entire system may be co-planar, implying that the system may have formed from the early
fragmentation of an individual protostellar core.