Title: A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs,
Abstract: We report the discovery of three small transiting planets orbiting GJ 9827, a
bright (K = 7.2) nearby late K-type dwarf star. GJ 9827 hosts a $1.62\pm0.11$
$R_{\rm \oplus}$ super Earth on a 1.2 day period, a $1.269^{+0.087}_{-0.089}$
$R_{\rm \oplus}$ super Earth on a 3.6 day period, and a $2.07\pm0.14$ $R_{\rm
\oplus}$ super Earth on a 6.2 day period. The radii of the planets transiting
GJ 9827 span the transition between predominantly rocky and gaseous planets,
and GJ 9827 b and c fall in or close to the known gap in the radius
distribution of small planets between these populations. At a distance of 30
parsecs, GJ 9827 is the closest exoplanet host discovered by K2 to date, making
these planets well-suited for atmospheric studies with the upcoming James Webb
Space Telescope. The GJ 9827 system provides a valuable opportunity to
characterize interior structure and atmospheric properties of coeval planets
spanning the rocky to gaseous transition.