The orbits of close binary stars can shrink as material ejected by the stars leads to friction and decay of their orbits. Through this process, the pair of stars can move so close together that they merge into a single star. This article describes one case of a stellar merger that led to an outburst of activity which was observed from the resulting star. The results of this article can help astronomers better understand this type of stellar system.
http://www.raa-journal.org/raa/index.php/raa/article/view/2625