A System of Three Super Earths Transiting the Late K-Dwarf GJ 9827 at Thirty Parsecs

摘要

We report the discovery of three small transiting planets orbiting GJ 9827, abright (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 transitingGJ 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 radiusdistribution of small planets between these populations. At a distance of 30parsecs, GJ 9827 is the closest exoplanet host discovered by K2 to date, makingthese planets well-suited for atmospheric studies with the upcoming James WebbSpace Telescope. The GJ 9827 system provides a valuable opportunity tocharacterize interior structure and atmospheric properties of coeval planetsspanning the rocky to gaseous transition.