Radial velocities of K2-291 with HIRES & HARPS-N

From the K2 C13 data, we found one super-Earth planet (R_p_=1.589_-0.072_^+0.095^ R_{Earth}_) transiting this star on a short period orbit (P=2.225177_-6.8e-5_^+6.6e-5^ days). We followed this system up with adaptive-optic imaging and spectroscopy to derive stellar parameters, search for stellar companions, and determine a planet mass.

From our 75 radial velocity measurements using High Resolution Echelle Spectrometer on Keck I and High Accuracy Radial velocity Planet Searcher in the northern hemisphere on Telescopio Nazionale Galileo, we constrained the mass of K2-291 b to M_p_=6.49+/-1.16 M_{Earth}_. We found it necessary to model correlated stellar activity radial velocity signals with a Gaussian process (GP) in order to more accurately model the effect of stellar noise on our data; the addition of the GP also improved the precision of this mass measurement.