Accretion Signatures in White Dwarfs: From Isolated Systems to Planetary Nebulae

Accretion onto white dwarfs is a key probe of late-stage stellar evolution, planetary system remnants, and binary interactions. I present X-ray accretion rate determinations for several benchmark white dwarfs using Chandra archival data and Sherpa spectral modeling with absorbed cooling flow models. For G29-38, my derived accretion rate agrees with recent published values, validating our analysis pipeline. I extend this method to the Be + white dwarf system π Aqr, finding results consistent with expectations from the literature. Application to the central white dwarf of the Helix Nebula (WD 2226-210) reveals additional challenges, including nebular background contamination, highlighting the limitations of simple absorption treatments in planetary nebula environments. Our findings demonstrate both the reliability and constraints of cooling flow modeling across different white dwarf populations and provide a foundation for expanding to a larger sample and developing standard accretion models.