Kepler-445, Kepler-446 and the Occurrence of Compact Multiples Orbiting mid-M Dwarf Stars

We confirm and characterize the exoplanetary systems Kepler-445 and Kepler-446: two mid-M dwarf stars, each with multiple, small, short-period transiting planets. Kepler-445 is a metal-rich ([ Fe/H] = + 0.25 0.10) M4 dwarf with three transiting planets, and Kepler-446 is a metal-poor ([ Fe/H] = -0.30 0.10) M4 dwarf also with three transiting planets. Kepler-445c is similar toGJ 1214b: both in planetary radius and the properties of the host star. The Kepler-446 system is similar to the Kepler-42 system: both are metal-poor with large galactic space velocities and three short-period, likely rocky transiting planets that were initially assigned erroneously large planet-to-star radius ratios. We independently determined stellar parameters from spectroscopy and searched for and fitted the transit light curves for the planets, imposing a strict prior on stellar density in order to remove correlations between the fitted impact parameter and planet-to-star radius ratio for short-duration transits. Combining Kepler-445, Kepler-446, and Kepler-42, and isolating all mid-M dwarf stars observed by Kepler with the precision necessary to detect similar systems, we calculate that 21+ 7 -5 % of mid-M dwarf stars host compact multiples ( multiple planets with periods of less than 10 days) for a wide range of metallicities. We suggest that the inferred planet masses for these systems support highly efficient accretion of protoplanetary disk metals by mid-M dwarf protoplanets.

NATURVETENSKAP Fysik Astronomi, astrofysik och kosmologi hsv//swe
NATURAL SCIENCES Physical Sciences Astronomy, Astrophysics and Cosmology hsv//eng
planetary systems
stars: fundamental parameters
stars: individual (KOI-2704
KOI-2842
Kepler-42
Barnard's Star)
stars: late-type
stars: low-mass

Mann, Andrew W. (author)
Vanderburg, Andrew (author)
Morton, Timothy D. (author)
Kraus, Adam (author)
Ireland, Michael (author)
Swift, Jonathan J. (author)
Feiden, Gregory A.Uppsala universitet,Teoretisk astrofysik(Swepub:uu)grefe950 (author)
Gaidos, Eric (author)
Gazak, J. Zachary (author)
Uppsala universitetTeoretisk astrofysik (creator_code:org_t)

By the author/editor: Muirhead, Philip ...; Mann, Andrew W.; Vanderburg, Andr ...; Morton, Timothy ...; Kraus, Adam; Ireland, Michael; show more...; Swift, Jonathan ...; Feiden, Gregory ...; Gaidos, Eric; Gazak, J. Zachar ...; show less...

About the subject

NATURAL SCIENCES: NATURAL SCIENCES; and Physical Science ...; and Astronomy Astrop ...

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