Molly Kosiarek, University of California, Santa CruzFollow
Ian J. M. Crossfield, University of California, Santa Cruz
Kevin K. Hardegree-Ullman, University of Toledo
John H. Livingston, University of TokyoFollow
Björn Benneke, Université de MontréalFollow
Gregory W. Henry, Tennessee State UniversityFollow
Ward S. Howard, University of North Carolina at Chapel Hill
David A. Berardo, Massachusetts Institute of TechnologyFollow
Sarah C. Blunt, California Institute of TechnologyFollow
Benjamin J. Fulton, California Institute of TechnologyFollow
Lea A. Hirsch, University of California - BerkeleyFollow
Andrew W. Howard, California Institute of TechnologyFollow
Howard Isaacson, University of California - BerkeleyFollow
Erik A. Petigura, California Institute of TechnologyFollow
Evan Sinukoff, University of Hawaii at ManoaFollow
Lauren M. Weiss, University of MontrealFollow
Xavier Bonfils, Université Grenoble AlpesFollow
Courtney D. Dressing, University of California - Berkeley
Heather Knutson, California Institute of TechnologyFollow
Joshua E. Schlieder, NASA Goddard Space Flight Center
Michael Werner, NASA Jet Propulsion LaboratoryFollow
Varoujan Gorjian, NASA Jet Propulsion LaboratoryFollow
Jessica Krick, California Institute of TechnologyFollow
Farisa Y. Morales, California Institute of TechnologyFollow
Nicola Astudillo-Defru, Université de GenèveFollow
J. M. Almenara, Université de Genève
Xavier Delfosse, Université Grenoble AlpesFollow
Thierry Forveille, Université Grenoble AlpesFollow
Christophe Lovis, Observatoire astronomique de l’Université de Genève
Michel Mayor, Observatoire astronomique de l’Université de Genève
Felipe Murgas, Instituto de Astrofśica de Canarias
Francesco Pepe, Observatoire astronomique de l’Université de Genève
Nuno C. Santos, Universidade do PortoFollow
Stephane Udry, Observatoire astronomique de l’Université de Genève
Henry T. Corbett, University of North Carolina at Chapel Hill
Octavi Fors, University of North Carolina at Chapel Hill
Nicholas M. Law, University of North Carolina at Chapel Hill
Jeffrey K. Ratzloff, University of North Carolina at Chapel Hill
Daniel del Ser, University of North Carolina at Chapel Hill

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We report improved masses, radii, and densities for four planets in two bright M-dwarf systems, K2-3 and GJ3470, derived from a combination of new radial velocity and transit observations. Supplementing K2 photometry with follow-up Spitzer transit observations refined the transit ephemerides of K2-3 b, c, and d by over a factor of 10. We analyze ground-based photometry from the Evryscope and Fairborn Observatory to determine the characteristic stellar activity timescales for our Gaussian Process fit, including the stellar rotation period and activity region decay timescale. The stellar rotation signals for both stars are evident in the radial velocity data and is included in our fit using a Gaussian process trained on the photometry. We find the masses of K2-3 b, K2-3 c, and GJ3470 b to be 6.48${}_{-0.93}^{+0.99}$, 2.14${}_{-1.04}^{+1.08}$, and 12.58${}_{-1.28}^{+1.31}$ M⊕, respectively. K2-3 d was not significantly detected and has a 3σ upper limit of 2.80 M⊕. These two systems are training cases for future TESS systems; due to the low planet densities (ρ < 3.7 g cm−3) and bright host stars (K < 9 mag), they are among the best candidates for transmission spectroscopy in order to characterize the atmospheric compositions of small planets.

Available for download on Saturday, January 01, 2022