A population of planetary systems characterized by short-period,   Earth-sized planets
  We analyze data from the Quarter 1-17 Data Release 24 (Q1--Q17 DR24) planet candidate catalog from NASA's Kepler mission, specifically comparing systems with single transiting planets to systems with multiple transiting planets, and identify a distinct population of exoplanets with a necessarily distinct system architecture. Such an architecture likely indicates a different branch in their evolutionary past relative to the typical Kepler system. The key feature of these planetary systems is an isolated, Earth-sized planet with a roughly one-day orbital period. We estimate that at least 24 of the 144 systems we examined (>~17%) are members of this population. Accounting for detection efficiency, such planetary systems occur with a frequency similar to the hot Jupiters. 
Jason H. Steffen (1) and Jeffrey L. Coughlin (2,3) ((1) University of   Nevada, Las Vegas, Department of Physics and Astrono...
astro-ph.EP