OGLE-2019-BLG-0960 Lb: the Smallest Microlensing Planet
- 6 October 2021
- journal article
- research article
- Published by American Astronomical Society in The Astronomical Journal
- Vol. 162 (5), 180
- https://doi.org/10.3847/1538-3881/ac1582
Abstract
We report the analysis of OGLE-2019-BLG-0960, which contains the smallest mass-ratio microlensing planet found to date (q = 1.2-1.6 x 10(-5) at 1 sigma). Although there is substantial uncertainty in the satellite parallax measured by Spitzer, the measurement of the annual parallax effect combined with the finite source effect allows us to determine the mass of the host star (M-L = 0.3-0.6 M-circle dot), the mass of its planet (m(p) = 1.4-3.1 M-circle plus), the projected separation between the host and planet (a(perpendicular to) = 1.2-2.3 au), and the distance to the lens system (D-L = 0.6-1.2 kpc). The lens is plausibly the blend, which could be checked with adaptive optics observations. As the smallest planet clearly below the break in the mass-ratio function, it demonstrates that current experiments are powerful enough to robustly measure the slope of the mass-ratio function below that break. We find that the cross-section for detecting small planets is maximized for planets with separations just outside of the boundary for resonant caustics and that sensitivity to such planets can be maximized by intensively monitoring events whenever they are magnified by a factor A > 5. Finally, an empirical investigation demonstrates that most planets showing a degeneracy between (s > 1) and (s < 1) solutions are not in the regime (vertical bar log s vertical bar >> 0) for which the "close"/"wide" degeneracy was derived. This investigation suggests that there is a link between the "close"/"wide" and "inner/outer" degeneracies and also that the symmetry in the lens equation goes much deeper than symmetries uncovered for the limiting cases.Keywords
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