The Observational Survey of Variable Objects Group studies mainly time-varying phenomena of variable objects such as eclipsing binaries, pulsating stars, and extrasolar planets, and their physical properties, using various methods. This research project has been active since 2007 using the photometric and spectroscopic facilities operated by KASI. By comparing observational results with theoretical models, we can study the formation and evolution of both planets and stars. Further, we are currently participating in approximately 10 multi-site observation campaigns related to these objects, such as the MicroFUN, EXOTIME, DWARF, WET, and KASC SWG projects.
The discovery of extrasolar planets, especially Earth-like planets in habitable zones, is in the spotlight both scientifically and socially because it is the first step in determining whether life exists in the universe outside of Earth. This is why the survey of extrasolar planets is commonly ranked as an interesting key research topic for recent projects involving the construction of large space- or ground-based telescopes.
Our research activities resulted in the first discovery of a multiple-planet system orbiting two parent stars, in 2009-02. These circumbinary planets are the first ones unequivocally discovered using the eclipse timing method. Circumbinary objects may have played an important role in the formation and evolution of the binary stars, which would cause them to have a short initial orbital period and thus evolve into a contact configuration due to angular momentum loss. To search for and study the origin of low-amplitude and long-period radial velocity (RV) variations, we conducted a precise RV survey of 55 K and 6 F (super)giants since 2003 using the echelle spectrograph attached to the 1.8-m telescope at BOAO. As a result, we discovered over ten extrasolar planets around giant stars. The discovery and interpretation of data on planets orbiting evolved stars helps us understand diverse planetary systems.