Mass Production 2021 KMTNet Microlensing Planets. I.

While we ultimately plan to quickly publish all 2021 planets meeting some minimal criteria, the current sample of four was chosen simply on the basis of having low initial estimates of the planet-host mass ratio, q. It is therefore notable that two members of this sample suffer from a degeneracy in the normalized source radius {rho} arises from different morphologies of closely spaced caustics.

All four planets (KMT-2021-BLG-1391, KMT-2021-BLG-1253, KMT-2021-BLG-1372, KMT-2021-BLG-0748) have well-characterized mass ratios, q, and therefore are suitable for mass-ratio frequency studies. Both of the {rho} degeneracies can be resolved by future adaptive optics (AO) observations on 30m class telescopes. We provide general guidance for such AO observations for all events in anticipation of the prospect that they will revolutionize the field of microlensing planets.