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

TL;DR

This paper reports the discovery of three small transiting super Earths around the nearby star GJ 9827, highlighting their potential for atmospheric and interior characterization, especially with upcoming telescopes.

Contribution

First discovery of a three-planet super Earth system around GJ 9827, with planets spanning the rocky to gaseous transition, suitable for detailed follow-up studies.

Findings

Three super Earths with radii 1.27-2.07 R_⊕ orbiting GJ 9827

Planets' radii span the transition between rocky and gaseous worlds

Closest exoplanet host discovered by K2 at 30 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.