Kepler-445, Kepler-446 and the occurrence of compact multiples orbiting mid-M dwarf stars
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Published version
Date
2015-03-01
Authors
Muirhead, Philip S.
Mann, Andrew W.
Vanderburg, Andrew
Morton, Timothy D.
Kraus, Adam
Ireland, Michael
Swift, Jonathan J.
Feiden, Gregory A.
Gazak, J. Zachary
Version
OA Version
Citation
Philip S Muirhead, Andrew W Mann, Andrew Vanderburg, Timothy D Morton, Adam Kraus, Michael Ireland, Jonathan J Swift, Gregory A Feiden, Eric Gaidos, J Zachary Gazak. 2015. "KEPLER -445, KEPLER -446 AND THE OCCURRENCE OF COMPACT MULTIPLES ORBITING MID-M DWARF STARS." The Astrophysical Journal, Volume 801, Issue 1, pp. 18 - 18.
Abstract
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 to GJ 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.
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© 2015 American Astronomical Society