The prime Kepler mission revealed that small planets ( < 4 R _ { \oplus } ) are common , especially around low-mass M dwarfs . K 2 , the re-purposed Kepler mission , continues this exploration of small planets around small stars .
Here we combine K 2 photometry with spectroscopy , adaptive optics imaging , and archival survey images to analyze two small planets orbiting the nearby , field age , M dwarfs K2-26 ( EPIC 202083828 ) and K2-9 .
K2-26 is an \mathrm { M 1.0 \pm 0.5 } dwarf at 93 \pm 7 pc from K 2 Campaign 0 .
We validate its 14.5665 d period planet and estimate a radius of \mathrm { 2.67 ^ { +0.46 } _ { -0.42 } ~ { } R _ { \oplus } } .
K2-9 is an \mathrm { M 2.5 \pm 0.5 } dwarf at 110 \pm 12 pc from K 2 Campaign 1 .
K2-9b was first identified by ( ) ; here we present spectra and adaptive optics imaging of the host star and independently validate and characterize the planet .
Our analyses indicate K2-9b is a \mathrm { 2.25 ^ { +0.53 } _ { -0.96 } ~ { } R _ { \oplus } } planet with a 18.4498 d period .
K2-26b exhibits a transit duration that is too long to be consistent with a circular orbit given the measured stellar radius .
Thus , the long transits are likely due to the photoeccentric effect and our transit fits hint at an eccentric orbit .
Both planets receive low incident flux from their host stars and have estimated equilibrium temperatures < 500 K. K2-9b may receive approximately Earth-like insolation .
However , its host star exhibits strong GALEX UV emission which could affect any atmosphere it harbors .
K2-26b and K2-9b are representatives of a poorly studied class of small planets with cool temperatures that have radii intermediate to Earth and Neptune .
Future study of these systems can provide key insight into trends in bulk composition and atmospheric properties at the transition from silicate dominated to volatile rich bodies .