You Shall Not Pass (Without Modeling): High-Resolution Analysis of KMT-2019-BLG-0253 using MORIA

We present the Microlensing Object high-Resolution Imaging Analysis pipeline, or MORIA. This is an automated procedure to reduce high-resolution HST images of microlensing targets, build empirical point-spread function models from the data, and perform simultaneous multi-star PSF fitting to blended sources, lenses, and neighbor stars. We have developed and tested this pipeline using HST observations of the microlensing event KMT-2019-BLG-0253, where we determine a host mass of M host = 0.65 plus or minus 0.04M. We have reduced the number of possible solutions for this target by a factor of two, with the remaining solution subject to the well-known close-wide degeneracy. We determine a planet mass of m p = 7.18 plus or minus 0.40 M (close) or m p = 9.48 plus or minus 1.13 M (wide), and distance to the lens system of D L= 2.64 plus or minus 0.22 kpc. This work demonstrates the importance of using an automated high resolution imaging tool to inform light curve modeling for microlensing planets found during the upcoming Nancy Grace Roman Galactic Bulge Time Domain Survey (GBTDS).