Analyzing the Variability of Central Stars of Planetary Nebulae

Close binary central stars are found at the center of about 10-15% of all planetary nebulae. These close binary systems’ light varies over time, due to different interactions between the two stars. The physical interaction of these close binary stars could have an effect on the shaping of the planetary nebulae around them. The interactions between the two stars could also explain why certain physical characteristics such as Jets and FLIERs (Fast, Low Ionization Emission Regions) form in planetary nebulae. Analysis of light variability and spectroscopy of these close binary stars can lead to determining physical characteristics of the stars and help to confirm whether or not binary central stars are the cause of the observed structures. Physical characteristics are found through modeling of the system and allow comparison of the characteristics of the binary central stars to physical characteristics of the surrounding planetary nebula. In addition to more general data reduction and analysis techniques, my research this summer has focused on the planetary nebula Hartl-Tritton 7 (HaTr 7). Multiple spectra and images have been taken of the central star of HaTr 7, confirming that this central star is a close binary. Computer modeling of the HaTr 7 central binary system is underway with the goal of linking its characteristics to the shape and physical characteristics of the HaTr 7 planetary nebula