Probing Circumstellar Envelopes with Gravitational Microlensing

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ABSTRACTIgnace, Richard"Probing Circumstellar Envelopes with Gravitational Microlensing"AST-9986915In this project a theoretical basis and observational methodology will be developed for interpreting stellar gravitational microlensing events that are discovered in the course of ongoing monitoring campaigns. Such events in principle can be used to 'gravitationally image' otherwise unresolvable stellar photospheric and circumstellar structures when an invisible but massive object passes between the observer and a background star. Current microlensing techniques are useful only by assuming normal symmetrical stellar photospheres. The PIs will extend the technique to include microlensing events that involve red giant stars. The latter have highly asymmetrical atmospheric structure, winds, and variations in envelope size, velocity and density. The technique developed also may be useful in categorizing lensing events in the nuclei of other nearby normal galaxies such as M31 and active galactic nuclei.Funding for this project was provided by the NSF program for Stellar Astronomy & Astrophysics (AST/SAA).