Sharif Digital Repository

One of the beautiful branches of Astrophysics is studing of binary systems and specially eclipsing binary sytems which is included transiting eclipsing extrasolar planets. Detecting of extrasolar planets with transit method is based on which a planet orbits around a star and when its orbit alignment is such that planet along our line of sight across disk of star, it causes eclipse of star and a drop in star’s brightness and from this we can find the existence of a planet. In analysis of observational light curve (obtained from data acquisition with photometry method) a synthetic light curve, constructed from a theoretical model which is based on transit, planet and star geometry, is... 

Gravitational Microlensing is one of the most powerful methods of detecting very low mass objects like Exoplanets and Brown dwarfs. The most important parameter that we can extract from a microlensing event is Einstein radius crossing time t_E. In this thesis, with performing Monte-Carlo simulation, we will obtain t_E distribution for brown dwarf population. Then we will show that this population can be a good candidate for very short microlensing events with t_E<2 days. The data set used in this analysis was taken in 2006 and 2007 seasons by the MOA-II survey, with the 1.8-m MOA-II telescope located at the Mt. John University Observatory, New Zealand  

In this thesis first we will review gravitational lensing and microlensing, then we will introduce all direct and indirect methods for detecting exo-planets. gravitational microlensing is one of these methods in detecting exo-planets. In the second part first we will explain a powerful numerical method for calculating magnification, position and the shape of images by combining of tree code and inverse rays hooting algorithm. Then we simulated the caustic crossing of Hot Jupiters using that algorithm. Finally with performing Monte-Carlo simulation we will obtain the detection efficiency for detecting this class of exo-planets during caustic crossing and we will estimate the number of these... 

The number of discovered extrasolar planetary systems has increased immensely during the past 15 years. The various outcomes of planetary formation are a result of the complicated interaction between gravitational, hydrodynamical and accretion processes a considerable amount of which is not yet understood. Thus far the effect of a planet embedded in a protoplanetary disk has been studied both analytically and using numerical simulations. These suggest that under suitable circumstances tidal effects result in the formation of a gap in the disk about the orbit of the planet. This result has been particularly used to detect massive extrasolar planets (massive enough to form gaps).In this study... 

With discovery of each exoplanet in habitable zone around a star, we expect to find life happening in the planet or it can be a place to move in. Life needs time to evolve. If our search is for complicated or intelligent type of life, there must be enough time for it i.e. billions of years. If the planet is ripped off of its life-supporting properties in midst of its evolution by a hazard, complicated species will not be born.In this thesis I examine the near stellar flyby hazard, which can send the planet out of the circumstellar habitable zone. In this research, by gravitational simulations, various near stellar encounters are studied and by using the environmental parameters around... 

Gravitational microlensing with the binary lenses are one the tools for detection of exoplanets. Due to the degeneracy nature of the solutions for the observed light curves additional features such as parallax and finite-size effects help to break the degeneracy. Here in this work we introduce the application of frequency shift effect in the microlensing observations where for the single lens, it has been studied in [5] .In this work our purpose is to study the frequency shifts in binary lenses. Therefore, after reviewing the frequency shift in single gravitational lens systems, we will study this phenomenon in binary systems.In binary lenses, which are mainly used to detect extrasolar...