Mass Measurements of Isolated Objects from Space-based Microlensing

Abstract

We report on the mass and distance measurements of two single-lens events from the 2015 \emph{Spitzer} microlensing campaign. With both finite-source effect and microlens parallax measurements, we find that the lens of OGLE-2015-BLG-1268 is very likely a brown dwarf. Assuming that the source star lies behind the same amount of dust as the Bulge red clump, we find the lens is a $45\pm 7$ $M_{\mathrm{J}}$ brown dwarf at $5.9\pm 1.0$ kpc. The lens of of the second event, OGLE-2015-BLG-0763, is a $0.50\pm 0.04$ $M_{\odot }$ star at $6.9\pm 1.0$ kpc. We show that the probability to definitively measure the mass of isolated microlenses is dramatically increased once simultaneous ground- and space-based observations are conducted.

10 papers, 4 figures, 2 tables; ApJ in press