| The search for brown dwarfs in binary systems is of great scientific interest and is a quest that pushes observing accuracy to its limit. The study of brown dwarfs is related to the search for dark matter, the initial mass function for stars of all masses, and theories of stellar formation. On the other hand, searching for brown dwarfs is a challenge because of their faintness and very low mass.; Although many techniques have been used to detect brown dwarfs, a direct measurement of mass is the only criterion for distinguishing a brown dwarf from a star, and binary observation is still the best way for determining the accurate masses of celestial objects through Kepler's third law. Since 1975, CHARA has accumulated thousands of binary star speckle observations with high precision that can be used to find masses of possible unseen companions in binary systems through astrometrically measured submotions. A modified discrete Fourier transform was used to detect periodicity in data sets having uneven temporal distributions.; This dissertation, an extension of work initiated by Dr. Ali Al-Shukri in 1991, uses the CHARA speckle measurements to evaluate their limiting accuracy and then, to search for unseen companions from submotions of binary orbital motions. The successful detection of the previously known 1.83-year period submotion of the astrometric system ADS 8119 Aa demonstrates that this analysis can be used to find other systems in future investigations, even though no convincing evidence was found for the existence of a brown dwarf. Four possible companions were found to the binaries ADS 8197, ADS 9392, ADS 9494, and ADS14073 with periods of 3.3, 2.6, 0.3, and 3.78 years and minimum masses in the ranges of 0.015-0.019, 0.11-0.65, 0.04-0.19, and 0.14-0.16 {dollar}Msbodot{dollar}, respectively. The overall null result for detecting brown dwarfs may be partially explained as a real lack of massive brown dwarfs as members of multiple systems. |
