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Unformatted text preview: arXiv:0811.0441v1 [astroph] 4 Nov 2008 Introduction to Gravitational Microlensing Shude Mao ∗ Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL, UK Email: [email protected] The basic concepts of gravitational microlensing are introduced. We start with the lens equation, and then derive the image positions and magnifications. The statistical quantities of optical depth and event rate are then described. We finish with a summary and a list of challenges and open questions. A problem set is given for students to practice. The Manchester Microlensing Conference: The 12th International Conference and ANGLES Microlensing Workshop January 2125 2008 Manchester, UK ∗ Speaker. c circlecopyrt Copyright owned by the author(s) under the terms of the Creative Commons AttributionNonCommercialShareAlike Licence. http://pos.sissa.it/ Introduction to Gravitational Microlensing Shude Mao 1. Introduction Gravitational microlensing (in the local group) refers to the temporal brightening of a back ground star due to intervening objects. Einstein (1936) first examined (micro)lensing by a single star, and concluded that “there is no great chance of observing this phenomenon.” Some important works were performed in intervening years by [46] and [34], but the research topic was revitalised by Paczy´nski (1986) who proposed it as a method to detect compact dark matter objects in the Galactic halo. The original goal is now out of favour, since we know with high precision that most of the dark matter must be nonbaryonic, e.g. from observations of microwave background radiation and nucleosynthesis (at the time of his paper, this was, however, unclear). Nevertheless, gravitational microlensing has turned into a powerful technique with diverse applications in astrophysics, includ ing the study of the structure of the Milky Way, stellar atmospheres and the detection of extrasolar planets and stellarmass black hole candidates. The field has made enormous progress in the last two decades. There have been a number of reviews on this topic (e.g. [39, 36, 20, 54]), the most recent highlight was given in [26]. This article gives an introduction to microlensing, aimed at a level for a starting PhD student. Together with other talks in the workshop and proceedings 1 , one can gain a thorough feeling about the stateoftheart research in this field (as of 2008). The reference list given here is seriously incomplete (and biased). For more complete refer ences and information about ongoing microlensing surveys, see the review papers mentioned above and the web site: http://mlens.net/ (built by Szymon Kozlowski, Subo Dong and Lukasz Wyrzykowski)....
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 Fall '10
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 General Relativity, Speak, Gravitational lens, Gravitational lensing, Gravitational microlensing, Einstein radius, Shude Mao

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