Finding Variability in Proto-Planetary Nebulae

We observed 44 evolved stars that are in the phase between red giants and white dwarfs. This stage is called proto-planetary nebulae (PPNe). We observed these objects on 33 clear nights this summer. Nearby comparison stars are also observed along with the PPNe each night. We then reduce these images to get quantitative measurements of the brightness of the PPNe in relation to the comparison stars. The measurements are then plotted as light curves to show the variation of brightness over time. This variation in light is due to pulsation of the PPNe. For our project we combined our data with observations made since 2008. We then analyzed the variation of light in a subset of 12 PPNe. We found periods of variation that range from 40 to 160 days