OGLE-2017-BLG-1434Lb: Confirmation of a Cold Super-Earth using Keck Adaptive Optics

Abstract

The microlensing event OGLE-2017-BLG-1434 features a cold super-Earth planet which is one of eleven microlensing planets with a planet-host star mass ratio $q < 1 \times 10^{-4}$. We provide an additional mass-distance constraint on the lens host using near-infrared adaptive optics photometry from Keck/NIRC2. We are able to determine a flux excess of $K_L = 16.96 \pm 0.11$ which most likely comes entirely from the lens star. Combining this with constraints from the large Einstein ring radius, $\theta_E=1.40 \pm 0.09\;mas$ and OGLE parallax we confirm this event as a super-Earth with mass $m_p = 4.43 \pm 0.25M_\odot$. This system lies at a distance of $D_L = 0.86 \pm 0.05\,kpc$ from Earth and the lens star has a mass of $M_L=0.234\pm0.012M_\odot$. We confirm that with a star-planet mass ratio of $q=0.57 \times 10^{-4}$, OGLE-2017-BLG-1434 lies near the inflexion point of the planet-host mass-ratio power law.