On the Feasibility of Characterizing Lens Stars in Future Space‐based Microlensing Surveys

If a light-emitting star is responsible for a gravitational microlensingevent, the lens can be characterized by analyzing the blended light from thelens. In this paper, we investigate the feasibility of characterizing lenses byusing this method in future space-based lensing surveys. To judge thefeasibility of the method, we estimate the portions of events whose blendedflux F_b can be firmly noticed and most of it can be attributed to the lens bycarrying out detailed simulations of Galactic bulge lensing events consideringvarious blending sources, including the lens, background stars, and binarycompanions to the lens and source. From this, it is estimated that among theevents to be detected from a survey using a 1 m space telescope, ~27% will haveblending fractions of F_b/F\geq 10% and the blended flux of half of theseevents will be contaminated more than (F_b-F_L)/F_b=20% by the flux fromblending sources other than the lens, implying the contamination of the blendedflux will be substantial. Although the contamination by the background starscan be reduced by using an instrument with a higher resolution, it is estimatedthat the blended flux of more than 1/3 of events will still be contaminated(mostly by binary companions) even using a telescope equivalent to the {\itHubble Space Telescope}, assuming 50% binary frequency. We, therefore, concludethat caution and consideration of the blending contaminants are required inapplying the lens-light analysis method.Comment: 4 pages, 2 figures, 1 table, ApJ, submitte