RUI: Using a Large Sample of White Dwarf Stars to Study Stellar Evolution

East Texas A&M University, Commerce TX

Investigators

Abstract

White dwarf (WD) stars are the endpoint of stellar evolution for the vast majority of stars. As such, they are useful forensic probes for studying the end stages of the stellar life cycle. A white dwarf is a compact star that contains the mass of the Sun within a volume comparable to that of the Earth (about a million times smaller). White dwarfs no longer undergo nuclear fusion like the Sun, but continue to glow from residual heat for billions of years. A research group at Texas A&M University-Commerce will carry out a program to use data from the Gaia space mission combined with observations from ground-based telescopes to double the sample of known WDs in young open clusters, or groupings of a few thousand stars of about the same age. These scientists will use this large sample of WDs to address several open questions in a range of astrophysical areas including: variability in total mass lost by stars during late stages of stellar evolution, the lower mass of the progenitors of supernovae, or stellar explosions, the evolution of close multiple star systems, and the fate of planetary systems. This project will expand an existing successful effort to improve undergraduate student learning and retention in introductory STEM classes by providing funding to train and mentor undergraduate learning assistants for revised, learner-centered introductory astronomy courses. The project will also offer first-generation college students and underrepresented students from depressed rural areas opportunities to participate in astronomy research. White dwarf stars in open star clusters are versatile and powerful forensic probes for studying the end stages of the stellar life cycle. In particular, white dwarf studies allow us to constrain the total mass lost by stars during their post-main sequence evolution, the lower mass limit for core-collapse supernova progenitors, the formation rate of double degenerate systems, rotation rates of red giant cores and their coupling to the star's envelope, and white dwarf atmospheric and structural evolution. White dwarfs in open star clusters are especially useful tools in large part because the many crucial stellar parameters are known, including total age (white dwarf cooling time plus progenitor lifetime) and metallicity. The project builds on earlier studies of white dwarf stars in open clusters made by the investigators; parallax and proper motion data from the Gaia mission and multi-epoch deep imaging of open clusters virtually eliminates uncertainties in cluster membership, vastly reducing the number of inferences currently made in the published literature. Through the use of national, state and local university facilities, the researchers expect to nearly double the number known open cluster white dwarfs and to be able to implement ensemble studies of white dwarf formation and evolution. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.