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Browsing by Author "Sabra, Bassem, Ph.D."

Browsing by Author "Sabra, Bassem, Ph.D."

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  • Examining the possibility of an ADAF as the main power source behind liner emissions 
    Der Sahaguian, Elias Ohannes (Notre Dame University-Louaize, 2019)
    Low-Ionization Nuclear Emission-Line Regions (LINERs) represent the low luminosity end of Active Galactic Nuclei (AGN). The main power source of LINERs is the subject of considerable debate in the scientific community today, despite the fact that some Liners show features of mass accretion into a super massive black hole (SMBH). Optical line-ratio diagrams are not conclusive diagnostic tools as they can be explained by different mechanisms, including shocks (Dopita et al. 1997[8]) and photoionization accompanied by outflow resembling accretion (Sabra et al. 2003[23]). This dissertation will ...
  • Nano cubesats for dark ages exploration 
    Malkoun, Marwan (Notre Dame University-Louaize, 2020-09)
    The Dark Ages, a period stretching from 400 thousand years to 400 million years after the big bang, is the least known era in the evolution of our universe, as no visible light was emitted. However, another type of radiation was available, the Hydrogen 21cm. It reaches us at frequencies between 1.5 and 30MHz. The ideal way to detect it, involves antennas placed in a fixed orbit around the dark side of the moon where it is shielded from electromagnetic interference emitted from earth.
  • Using quasars as standard candles : measuring distances up to redshifts4 
    Ismail, Diana (Notre Dame University-Louaize, 2019-02)
    In this thesis, we have restudied a sample chosen by (Lusso & Risaliti, 2016) consisting of a set of 2,153 unique quasars given by two source catalogues: 3XMM-DR5 (Rosen et al., 2016) and DR7 catalogue (Shen et al., 2011). Quasars serve science in two different ways: 1) Understanding accretion physics by studying the physical mechanism occuring between the disk and cloud corona, and 2) they are good cosmological probes in distance estimation reaching redshifts ~ 7 (Mortlock et al., 2011). A physical relation has been observed between the optical-UV disk and the X-ray corona through a log-log ...