EPIC 247418783b: A rocky super-Earth in a 2.2 day orbit

PIC 247418783 is a solar-type star with a radius of R_★ = 0.899 ± 0.034 R_⊙ and mass of M_★=0.934 ± 0.038 M_⊙ . From K2 C13 data, we found one super-Earth planet (R_p = 1.589^(+0.095)_(-0.072) R_⊕) transiting this star on a short period orbit (P = 2.225177 ^(+6.6e-5)_ (-6.8e-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 HIRES on Keck I and HARPS-N on Telescopio Nazionale Galileo, we constrained the mass of EPIC 247418783b to M_p = 6.49 ± 1.16 M_⊕. We found it necessary to model correlated stellar activity radial velocity signals with a Gaussian process in order to more accurately model the effect of stellar noise on our data; the addition of the Gaussian process also improved the precision of this mass measurement. With a bulk density of 8.84^(+2.50)_(-2.03) g cm^(-3), the planet is consistent with an Earth-like rock/iron composition and no substantial gaseous envelope. Such an envelope, if it existed in the past, was likely eroded away by photo-evaporation during the first billion years of the star's lifetime.