A public code for astrometric microlensing with contour integration

Abstract

We present the first public code for the calculation of the astrometric centroid shift occurring during microlensing events. The computation is based on the contour integration scheme and covers single and binary lensing of finite sources with arbitrary limb darkening profiles. This allows for general detailed investigations of the impact of finite source size in astrometric binary microlensing. The new code is embedded in version 3.0 of VBBinaryLensing, which offers a powerful computational tool for extensive studies of microlensing data from current surveys and future space missions.

MOA-2006-BLG-074: recognizing xallarap contaminants in planetary microlensing

“…In order to explore the parameter space, we use the RTModel platform 1 , which is based on a template library approach (Mao & Di Stefano 1995). The basic magnification calculation is performed by the V BBinaryLensing code (Bozza 2010;Bozza et al 2018;Bozza et al 2020). With this approach, we find two planetary solutions with s < 1, and their corresponding wide duals with s → 1/s (Dominik 1999;Griest & Safizadeh 1998).…”

“…In many cases, it is sufficient to approximate the orbital motion by using constant values of these two quantities (Hwang et al 2010b). However, since such approximation does not correspond to a physical orbital motion, we prefer to study models including the component of the angular velocity along the line of sight γ z = (ds z /dt)/s (Skowron et al 2011;Bozza et al 2020). With the assumption of circular orbital motion, these three parameters are sufficient to completely characterize the orbit and thus allow us to explore a sub-space of possible physical solutions, as opposed to the two-parameter linear orbital motion.…”