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Probing the Universe with Gravitational Microlensing

Khalouei, Elaheh | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54206 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Rahvar, Sohrab; Sajadian, Sedigheh
  7. Abstract:
  8. Gravitational microlensing is one of the experimental tests to confirm the theory of general relativity. In this phenomenon, the light of the source star is deflected by the gravitational field of the foreground star which plays the role of the lens. As a result of this deviation, images of source star are formed on the sky plane. The observer records the light of the source star as a variable with time. The gravitational microlensing illustrates the possibility to discover extrasolar planets, study the atmosphere of stars, and probe the nature of Dark matter. In this thesis, at first, we introduce the basic concepts of gravitational microlensing and its history. Then by simulation of gravitational microlensing events in the galactic bulge, we examine the efficiency of simultaneous photometry and polarimetry observation for gravitational microlensing events. Also, we indicate how these observations help us to concentrate the atmosphere of stars. In the next part, we study the astrometry of stars and extrasolar planets by introducing the astrometry concept of gravitational microlensing events. Then we present a report of papers published through observational activities that have been done. In the last part, we examine the effect of gravitational microlensing on gravitational waves. We introduce primordial black holes as a source of gravitational waves. Assuming that PBHs are the constituent components of dark matter halos, we estimate the rate at which these objects make binaries, merge, and produce GWs. Finally, We show that the primordial black holes cannot be the source of detected gravitational waves and the effect of microlensing on the amplitude of gravitational waves can be neglected regarding the sensitivity of today's detectors
  9. Keywords:
  10. Gravitational Microlensing ; Photometry ; Gravitational Waves ; Primordial Black Holes ; Polarimetry ; Dark Matter Halo

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