OGLE-2017-BLG-1434Lb: Confirmation of a cold super-Earth using Keck adaptive optics

The microlensing event OGLE-2017-BLG-1434 features a cold super-Earth planet that is 1 of 11 microlensing planets with a planet–host-star mass ratio of q < 1 × 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 ± 0.11, which most likely comes entirely from the lens star. Combining this with constraints from the large Einstein ring radius, θ_E = 1.40 ± 0.09 mas, and OGLE parallax we confirm this event as a super-Earth with a mass of m_p = 4.43 ± 0.25M_⊕. This system lies at a distance of D_L = 0.86 ± 0.05 kpc from Earth and the lens star has a mass of M_L = 0.234 ± 0.012M_⊙. We confirm that with a star–planet mass ratio of q = 0.57 × 10^-4, OGLE-2017-BLG-1434 lies near the inflexion point of the planet–host mass-ratio power law.