Using Astrometry to Deblend Microlensing Events

Abstract

We discuss the prospect of deblending microlensing events by observing astrometric shifts of the lensed stars. Since microlensing searches are generally performed in very crowded fields, it is expected that stars will be confusion limited rather than limited by photon statistics. By performing simulations of events in crowded fields, we find that if we assume a dark lens and that the lensed star obeys a power law luminosity function, $n(L)\propto L^{-\beta }$, over half the simulated events show a measurable astrometric shift. Our simulations included 20000 stars in a $256\times 256$ Nyquist sampled CCD frame. For $\beta =2$, we found that 58% of the events were significantly blended $(F_{\ast }/F_{tot}\le 0.9)$, and of those, 73% had a large astrometric shift $(\ge 0.5pixels)$. Likewise, for $\beta =3$, we found that 85% of the events were significantly blended, and that 85% of those had large shifts. Moreover, the shift is weakly correlated to the degree of blending, suggesting that it may be possible not only to detect the existence of a blend, but also to deblend events statistically using shift information.

24 pages, 7 postscript Figures

References in corpus (3)

• Microlensing of Blended Stellar Images
• First detection of a gravitational microlensing candidate towards the Small Magellanic Cloud
• Correction for Blending Problem in Gravitational Microlensing Events by Using Hubble Space Telescope

Cited by in corpus (12)

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• Detection Efficiencies of Microlensing Datasets to Stellar and Planetary Companions
• Blending in Gravitational Microlensing Experiments: Source Confusion And Related Systematics
• WeCAPP - The Wendelstein Calar Alto Pixellensing Project I Tracing Dark and Bright Matter in M31
• On the Feasibility of Characterizing Lens Stars in Future Space-Based Microlensing Surveys
• Predicted microlensing events from analysis of Gaia Data Release 2
• On the Nature and Location of the Microlenses
• Analytic Relations between the Observed Gravitational Microlensing Parameters With and Without the Effect of Blending
• An Additional Application of the Space Interferometry Mission to Gravitational Microlensing Experiments
• Microlensing and the Search for Extraterrestrial Life
• Observational Evidence for the Effect of Amplification Bias in Gravitational Microlensing Experiments
• Blending in Future Space-based Microlensing Surveys