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Detection of Massive Black Holes with Gravitational Lensing Effects on Light Curves of Gamma-Ray Bursts Observed by Fermi Telescope

Kalantari, Zeinab | 2022

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 55779 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Rahvar, Sohrab; Rahimi Tabar, Mohammad Reza
  7. Abstract:
  8. In this thesis, we investigate the imprint of gravitational microlensing effects on the light curves of Gamma-ray burst (GRBs) to estimate compact object mass in the form of black holes in the Universe. We assume a point mass model of the gravitational lens and a geometry in which the source−lens are at the same direction that manifests in the GRB light curve as superimposed peaks by the time delay between the two images and searches the Fermi/GBM catalog. According to the sensitivity of our detection method, we consider microlensing events with a time delay on the order of 10 s due to point-mass lenses in the range of 〖10〗^5- 〖10〗^7 M_(⊙ ). We found one microlensed GRB candidate out of 2137 long with a duration of T_90≥2 s and bright (with a fluence of P≥〖10〗^(-7 ) erg/(〖cm〗^2 s)). GRBs searched from the year 2008 to 2020 in the Fermi/GBM archive, using the autocorrelation technique and from parameters of the light curve of this candidate, we determine that the lens is a black hole with the redshifted mass M(1+z) of about a million solar masses. By performing a Monte Carlo simulation to find the efficiency of our detection method and with an estimation of the optical depth, we show that the fraction of dark matter in the form of a black hole to the total matter of the universe is about 0.007±0.004. Finally, Minimizing χ^2we confirm the mass of this gravitational lens.

  9. Keywords:
  10. Black Holles ; Gravitational Lensing ; Gamma-Ray Bursts ; Gravitational Microlensing ; Autocorrelation

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