Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs. (arXiv:1906.10147v1 [astro-ph.EP])

Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M Dwarf System at 6.9 Parsecs. (arXiv:1906.10147v1 [astro-ph.EP])
<a href="http://arxiv.org/find/astro-ph/1/au:+Winters_J/0/1/0/all/0/1">Jennifer G. Winters</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Medina_A/0/1/0/all/0/1">Amber A. Medina</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Irwin_J/0/1/0/all/0/1">Jonathan M. Irwin</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charbonneau_D/0/1/0/all/0/1">David Charbonneau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Astudillo_Defru_N/0/1/0/all/0/1">Nicola Astudillo-Defru</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Horch_E/0/1/0/all/0/1">Elliott P. Horch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Eastman_J/0/1/0/all/0/1">Jason D. Eastman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vrijmoet_E/0/1/0/all/0/1">Eliot Vrijmoet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henry_T/0/1/0/all/0/1">Todd J. Henry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Diamond_Lowe_H/0/1/0/all/0/1">Hannah Diamond-Lowe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Winston_E/0/1/0/all/0/1">Elaine Winston</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonfils_X/0/1/0/all/0/1">Xavier Bonfils</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ricker_G/0/1/0/all/0/1">George R. Ricker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vanderspek_R/0/1/0/all/0/1">Roland Vanderspek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Latham_D/0/1/0/all/0/1">David W. Latham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Seager_S/0/1/0/all/0/1">Sara Seager</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Winn_J/0/1/0/all/0/1">Joshua N. Winn</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jenkins_J/0/1/0/all/0/1">Jon M. Jenkins</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Udry_S/0/1/0/all/0/1">St'ephane Udry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Twicken_D/0/1/0/all/0/1">Dr. Joseph D. Twicken</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Teske_J/0/1/0/all/0/1">Johanna K. Teske</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Tenenbaum_P/0/1/0/all/0/1">Peter Tenenbaum</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pepe_F/0/1/0/all/0/1">Francesco Pepe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Murgas_F/0/1/0/all/0/1">Felipe Murgas</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Muirhead_P/0/1/0/all/0/1">Philip S. Muirhead</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mink_J/0/1/0/all/0/1">Jessica Mink</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lovis_C/0/1/0/all/0/1">Christophe Lovis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Levine_A/0/1/0/all/0/1">Alan M. Levine</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lepine_S/0/1/0/all/0/1">S'ebastien L'epine</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Jao_W/0/1/0/all/0/1">Wei-Chun Jao</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Henze_C/0/1/0/all/0/1">Christopher E. Henze</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Furesz_G/0/1/0/all/0/1">G'abor Fur'esz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Forveille_T/0/1/0/all/0/1">Thierry Forveille</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Figueira_P/0/1/0/all/0/1">Pedro Figueira</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Esquerdo_G/0/1/0/all/0/1">Gilbert A. Esquerdo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dressing_C/0/1/0/all/0/1">Courtney D. Dressing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Diaz_R/0/1/0/all/0/1">Rodrigo F. D'iaz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Delfosse_X/0/1/0/all/0/1">Xavier Delfosse</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Burke_C/0/1/0/all/0/1">Chris J. Burke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bouchy_F/0/1/0/all/0/1">Franois Bouchy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Berlind_P/0/1/0/all/0/1">Perry Berlind</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Almenara_J/0/1/0/all/0/1">Jose-Manuel Almenara</a>

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 follow-up observations from MEarth
and the centroid offset analysis in the TESS data validation report to
determine that the planet transits the primary star in the system. The planet
has a radius 1.35 R_Earth, an orbital period of 5.35882 days, and an
equilibrium temperature of 428 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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