The Combined System of Microlensing Exoplanets and Their Host Stars

Abstract

If the direction to a foreground star (the lens) and a background star (the source) is aligned to within approximately a milli-arc second (mas), then the foreground star will redirect light from the background star, thereby increasing its apparent brightness, forming a microlensing event. The light curve, i.e., the increase in source brightness as function of time, mainly contain information about the lens star and its exoplanets, but higher order details also depend on the source star and its possible exoplanets, so the most detailed analyses require simultaneous model fit to all the components. The models can reveal the mass and dynamics of the system but can also reveal details of, for example, the atmospheric structure of the source star. Microlensing is an optimal method to obtain unbiased information about the stellar lens population, detailed information about the source star atmosphere, and statistics on exoplanets with mass and orbits similar to the planets in the solar system, including planets beyond the snow line and even unbound planets. Microlensing events can be found in a wide distance range throughout our own Galaxy, as well as in principle in other galaxies too.