SW Bootis
SW Bootis is a bright type ab RR Lyrae star with a period of just over half a day. Discovered in 1914, studies over the succeeding decades suggested that SW Boo's period was changing, either in sudden jumps or with a smoothly increasing. Taylor (1978) analyzed the earlier photographic observations as well as visual estimates by Marvin Baldwin and determined that the star's maxima varied in amplitude in a 12.997d cycle, indicative of the Blazhko effect. However, a later study by Sódor & Jurcsik (2005) did not detect these variations.
Additional information
A New Look at SW Bootis (Taylor, Peter, JAVSO)
Revision of the List of Galactic Field RRab Starts with Known Blazhko Periods (Sodor & Jurcsic, IBVS)