An Observational Study of Variable Stars

This past summer, we carried out an observational study of light variability in approximately 20 stars. Our goal was to document their changes in brightness, determine a period of the variability, and investigate whether their brightness changes were correlated with changes in color (and thus temperature). These stars are part of a special class of stars that have evolved beyond the red giant phase but have not yet become white dwarfs. Little is known about their variability during this phase. We observed them on almost every clear night during the summer of 2010. We then compared the data for this summer with that of the previous two years. We determined tentative periods for roughly half of these, and they ranged from approximately 40 to 200 days. The brightness changes ranged from 10 to 40% and the objects in general were redder and cooler when fainter. The variation in brightness is due to pulsation of the stars