Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs
Abstract
We present the discovery from TESS data of LTT 1445Ab. At a distance of 6.9 parsecs, 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 data from MEarth and results from the SPOC DV report to determine that the planet transits the primary star in the system. The planet has a radius 1.38 R_Earth, an orbital period of 5.35882 days, and an equilibrium temperature of 433 K. With radial velocities from HARPS, we place a three-sigma upper mass limit of 8.4 M_Earth on the candidate. The planet provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. The presence of stellar companions of similar spectral type may facilitate such ground-based studies by providing a calibration source to remove telluric variations. In addition, we 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 indicates a moderate amount of variability, in agreement with the observed low-level, short-term variability 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 raises the possibility that the entire system is co-planar, which implies that the system may have formed from the early fragmentation of an individual protostellar core.
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Cite
@article{arxiv.1906.10147,
title = {Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs},
author = {Jennifer G. Winters and Amber A. Medina and Jonathan M. Irwin and David Charbonneau and Nicola Astudillo-Defru and Elliott P. Horch and Jason D. Eastman and Eliot Vrijmoet and Todd J. Henry and Hannah Diamond-Lowe and Elaine Winston and Thomas Barclay and Xavier Bonfils and George R. Ricker and Roland Vanderspek and David W. Latham and Sara Seager and Joshua N. Winn and Jon M. Jenkins and St'ephane Udry and Joseph D. Twicken and Johanna K. Teske and Peter Tenenbaum and Francesco Pepe and Felipe Murgas and Philip S. Muirhead and Jessica Mink and Christophe Lovis and Alan M. Levine and S'ebastien L'epine and Wei-Chun Jao and Christopher E. Henze and G'abor Fur'esz and Thierry Forveille and Pedro Figueira and Gilbert A. Esquerdo and Courtney D. Dressing and Rodrigo F. D'iaz and Xavier Delfosse and Chris J. Burke and Franois Bouchy and Perry Berlind and Jose-Manuel Almenara},
journal= {arXiv preprint arXiv:1906.10147},
year = {2024}
}
Comments
Accepted to AJ; 21 pages, 8 tables, 7 figures