Light Curve Analysis In Optical Survey And Statistics Of Hot Jupiters

As one of the most active and fast growing field in astronomy,exoplanetology has boosted itself in the past few decades through stable observational facilities,large space coverage and long time baseline.Ever since the first discovery of the first hot Jupiter(51 Peg b)detected around solar-type star,thousands of newly discovered exoplanets has been detected nearby our solar system.It is the detailed observations as well as accurate photometric pipelines that has been made possible for us to reveal the nature of both our solar system and alien worlds.We began by analyzing ghost image within a total of over 300,000 images ob-served during the Polar Night of 2008 at Dome A site(Antarctica).The Chinese Small Telescope ARray(CSTAR)gathered i-band photometric information of the 20 deg2 sky vicinity around the South Pole automatically and continuously.We carry out a se-ries of elaborate analyses and study on the origin and influence of the ghost images in each frame.The point source catalog has also been amended by removing the ghost image effects from the real overlapped stars.Thus,we are able to provide a gener-alized ghost reduction pipeline and improve the photometric precision of the stars in the CSTAR FOV for astronomic researches like transiting exoplanets,variable stars and stellar flares.Importance has been drawn from our work for the next generation surveys in Dome A site,like Antarctic Survey Telescopes(AST3-2).Then in our next chapter,new search for systems hosting eclipsing discs are in-troduced by using a complete sample of eclipsing binaries(EBs)in the third phase of the Optical Gravitational Lensing Experiment(OGLE-III).Within a subsample of 2823 high-cadence,high-photometric precision and large eclipsing depth detached EBs pre-viously identified in the Large Magellanic Cloud(LMC),we find that the skewness and kurtosis of the light-curve magnitude distribution within the primary eclipse can distinguish EBs with a complex-shaped eclipse from those without.Two systems with previously identified eclipsing discs(OGLE-LMC-ECL-11893 and OGLE-LMC-ECL-17782)are identified with near zero skewness(|S|<0.5)and positive kurtosis.No additional eclipsing disc systems were found in the OGLE-? LMC,Small Magellanic Cloud or Galactic Disc EB light curves.We estimate that the fraction of detached early-type LMC EBs(which have a primary with an I-band magnitude brighter than(?)19 mag)that exhibit atypical eclipses and so could host a disc is approximately 1/1000.As circumstellar disc lifetimes are short,we expected to primarily find eclipsing discs around young stars.In addition,as there is more room for a disc in a widely separated binary and because a disc close to a luminous star would be above the dust sublima-tion temperature,we expected to primarily find eclipsing discs in long-period binaries.However,OGLE-LMC-ECL-17782 is a 13.3 d period B star system with a transient and hot(?6000 K,?0.1 au radius)disc and Scott et al.(2014)estimate an age of 150 Myr for OGLE-LMC-ECL-11893.Both discs are unexpected in the EB sample and impel explanation.In chapter 4,known information of exoplanets are gathered for statistical ways of testing hot Jupiter theories.Recent observations of hot Jupiter obliquities has shown a dichotomy between those planets around hot and cool stars:hot Jupiters around hot stars have random obliquities,while those around cool stars are generally aligned.This dichotomy has been used as evidence that hot Jupiters form by a scattering process,with variations between hot and cool stars due to variations in the tidal dissipation effi-ciency(Qs/-value)and/or the stellar rotation speed between those stars.In particular,it is expected that cool stars have more efficient tidal dissipation and slower rotation and therefore,can re-align more efficiently.We revisit these scenarios taking into account the effects of equilibrium tides and stellar winds.We find that obliquity is anti-corre-lated with stellar spin around hot stars and that there is no correlation between stellar spin and orbital period for systems around cool stars.Both of these findings are incon-sistent with the hypothesis that slowly spinning stars may re-align their obliquity more easily.Our analyses demonstrates that a single value of Qs' can not explain all hot or cool star systems.Finally,using planets locked outside co-rotation with low obliquity we are able to constrain Qs' to be greater than 106.Last,Conclusion remarks are drawn in our final chapter by summarizing current and future plans of detecting more exoplanets and characterizing each individual planet.More physical processes and properties are in great demands.By placing samples of exoplanets within the historical environment of planetary formation,it could be possible to unlock more puzzles of our solar system and life itself in the near future.