Gravitational microlensing occurs when a massive lens (typically a star) deflects light from a more distant source, creating two unresolvable images that are magnified. The effect is transient due to the motions of the lens and source, and the changing magnification gives rise to a characteristic lightcurve. If the lensing object is a binary star or planetary system, more images are created and the lightcurve becomes more complicated. Detection of these lightcurve features allows the lens companion's presence to be inferred. Orbital motion of the binary lens can be detected in some microlensing events, but the expected fraction of events which show orbital motion has not been known previously. We use simulations of orbiting-lens microlensing events to determine the fraction of binary-lens events that are expected to show orbital motion. We also use the simulations to investigate the factors that affect this detectability. Following the discovery of some rapidly-rotating lenses in the simulations, we investigate the conditions necessary to detect lenses that undergo a complete orbit during a microlensing event. We find that such events are detectable and that they should occur at a low but detectable rate. We also derive approximate expressions to estimate the lens parameters, including the period, from the lightcurve. Measurement of the orbital period can in some cases allow the lens mass to be measured. Finally we develop a comprehensive microlensing simulator, MaBμLS, that uses the output of the Besançon Galaxy model to produce synthetic images of Galactic starfields. Microlensing events are added to the images and photometry of their lightcurves simulated. We apply these simulations to a proposed microlensing survey by the Euclid space mission to estimate its planet detection yield.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:549013 |
| Date | January 2011 |
| Creators | Penny, Matthew Thomas |
| Contributors | Mao, Shude ; Kerins, Eamonn |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/simulations-of-gravitational-microlensing(ddc24ee8-c2a6-432a-a168-7d56662a9247).html |
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