DETAILED ABUNDANCES of STARS with SMALL PLANETS DISCOVERED by KEPLER. I. the FIRST SAMPLE

Weresent newly derived stellararameters and the detailed abundances of 19 elements of seven stars with smalllanets discovered by NASA's Kepler Mission. Each star, save one, has at least onelanet with a radius ≤1.6 R_⊕, suggesting arimarily rocky composition. The stellararameters and abundances are derived from high signal-to-noise ratio, high-resolution echelle spectroscopy obtained with the 10 m Keck I telescope and High Resolution Echelle Spectrometer using standard spectroscopic techniques. The metallicities of the seven stars range from -0.32 to +0.13 dex, with an average metallicity that is subsolar, supportingrevious suggestions that, unlike Jupiter-type giantlanets, smalllanets do not formreferentially around metal-rich stars. The abundances of elements other than iron are in line with aopulation of Galactic disk stars, and despite our modest sample size, we find hints that the compositions of stars with smalllanets are similar to stars without knownlanets and with Neptune-sizelanets, but not to those of stars with giantlanets. This suggests that the formation of smalllanets does not require exceptional host-star compositions and that smalllanets may be ubiquitous in the Galaxy. We compare our derived abundances (which have typical uncertainties of ≲0.04 dex) to the condensation temperature of the elements; a correlation between the two has been suggested as aossible signature of rockylanet formation. None of the stars demonstrate theutative rockylanet signature, despite at least three of the stars having rockylanets estimated to contain enough refractory material toroduce the signature, if real. More detailed abundance analyses of stars known to host smalllanets are needed to verify our results andlace ever more stringent constraints onlanet formation models.