MOA-2020-BLG-208Lb: Cool Sub-Saturn-mass Planet within Predicted Desert

We analyze the MOA-2020-BLG-208 gravitational microlensing event and present the discovery and characterization of a new planet, MOA-2020-BLG-208Lb, with an estimated sub-Saturn mass. With a mass ratio q = 3.17(-0.26)(+0.28) x 10(-4), the planet lies near the peak of the mass-ratio function derived by the MOA collaboration and near the edge of expected sample sensitivity. For these estimates we provide results using two mass-law priors: one assuming that all stars have an equal planet-hosting probability, and the other assuming that planets are more likely to orbit around more massive stars. In the first scenario, we estimate that the lens system is likely to be a planet of mass m(planet) = 46(-24)(+42) M-circle plus and a host star of mass M-host = 0.43(-0.23)(+0.39) M-circle dot, located at a distance D-L = 7.49(-1.13)(+0.99) kpc. For the second scenario, we estimate m(planet) = 69(-34)(+37) M-circle plus, M-host = 0.66(-0.32)(+0.35) M-circle dot, and D-L = 7.81(-0.93)(+0.93) kpc. The planet has a projected separation as a fraction of the Einstein ring radius s = 1.3807(-0.0018)(+0.0018). As a cool sub-Saturn-mass planet, this planet adds to a growing collection of evidence for revised planetary formation models

Spitzer Microlensing Parallax Reveals Two Isolated Stars in the Galactic Bulge

We report the mass and distance measurements of two single-lens events from the 2017 Spitzer microlensing campaign. The ground-based observations yield the detection of finite-source effects, and the microlens parallaxes are derived from the joint analysis of ground-based observations and Spitzer observations. We find that the lens of OGLE-2017-BLG-1254 is a 0.60 ± 0.03 M⊙ star with DLS = 0.53 ± 0.11 kpc, where DLS is the distance between the lens and the source. The second event, OGLE-2017-BLG-1161, is subject to the known satellite parallax degeneracy, and thus is either a ${0.51}_{-0.10}^{+0.12}\,{M}_{\odot }$ star with DLS = 0.40 ± 0.12 kpc or a ${0.38}_{-0.12}^{+0.13}\,{M}_{\odot }$ star with DLS = 0.53 ± 0.19 kpc. Both of the lenses are therefore isolated stars in the Galactic bulge. By comparing the mass and distance distributions of the eight published Spitzer finite-source events with the expectations from a Galactic model, we find that the Spitzer sample is in agreement with the probability of finite-source effects occurring in single-lens events