Abstract
Several sky surveys identifying special objects of interest have been published in recent decades. As a result a large number of new variable stars have been discovered. In this research we are interested in binary systems discovered in globular clusters. In general, most eclipsing binaries are classified by light curve; W UMa type light curves are contact systems, Beta Lyrae type light curves are semidetached systems and Algol type light curves are detached systems and non-interactive. Among these eclipsing systems the detached systems could be used to derive the most reliable absolute dimensions. In our research we are concentrating on Algol type systems in globular clusters. We aim to derive the accurate absolute dimensions of binary components in these very old stars.
The respective locations of the components in the H-R diagram are determined from the derived absolute dimensions. Since the systems in our study have periods of factions of a day, they are unlikely to have been formed by capture. Thus both of the components of each binary system would have the same initial chemical composition. Further the components in a detached system are believed to evolve independently as two single stars. The evolution models of single stars are relatively well known. Thus, we hope to derive the age and metal index of the systems by fitting the evolutionary tracks to known locations of the components in the H-R diagram. By studying many systems among globular clusters we hope to establish a relationship between the ago and metal index. In some of the clusters more than one Algol system has been discovered. This enables us to determine different ages of star formation within a particular cluster.
The First Stars were formed after the Big-Bang. They are composed of just hydrogen and helium. Chemical elements heavier than helium (metal) were produced by fusion in the interior of stars. As stars die part of their mass recycles back to interstellar medium. Thus the medium will be continuously enriched with metal as new stars are formed and die. The globular clusters are very old. We hope that our study will give us insight into the chemical evolution of the early universe.
Coffee and tea will be served 20 minutes prior to the seminar.