INVESTIGATING WOLF-RAYET CENTRAL STARS OF PLANETARY NEBULAE
Seminars
Semester 2
Planetary nebulae (PNe) are the ejected glowing envelopes of low- to intermediate-mass stars whose central remnant cores (CSPNe) are hot and evolving towards white dwarfs. A subset of CSPNe are hydrogen-deficient with very fast winds that exhibit so-called Wolf-Rayet-like spectra designated as [WR] to distinguish them from their high mass short-lived counterpart WR stars. Studying these [WR] CSPNe, the objective of my project, provides special insights into later stage stellar evolution, nucleosynthesis process, binarity, and the chemical enrichment of the interstellar medium. In this study, we investigated the photometric variability of [WR] CSPNe using century-long plate data from the Digital Access to a Sky Century @ Harvard (DASCH) database, which is now available. Through DASCH data calibration and exploration of other survey data, our preliminary results indicate that several [WR] CSPNe exhibit significant photometric variability on timescales ranging from several years to more than half a century. This long-term variability offers insights into potential binary companions and unique, relatively short time dependencies in the evolutionary processes, such as a very late thermal pulse. A key discovery is the newly discovered variability observed in the exciting born-again planetary nebula HuBi 1, which will be discussed in detail in this presentation.
Additional information: Mr. Zhengjie TIAN, zhengjie@connect.hku.hk