UNC-CH Astronomy Journal Club

Jeffrey Cummings, John Hopkins University

“White Dwarfs in Star Clusters: The Initial-Final Mass Relation for Stars from 0.85 to 8 Solar Masses”

The spectroscopic study of white dwarfs provides both their mass, cooling age, and intrinsic photometric properties. For white dwarfs in the field of well-studied star clusters, this intrinsic photometry can be used to determine if they are members of that star cluster.

Comparison of a member white dwarf’s cooling age to its total cluster’s age gives the evolutionary timescale of its progenitor star, and hence the mass. This initial-final mass relation (IFMR) gives critical information on how a progenitor star evolves and loses mass throughout its lifetime, and how this changes with progenitor mass. Our work presents a uniform analysis of 85 white dwarfs spanning from progenitor masses of 0.85 to 8 solar masses. Comparison of our work to theoretical IFMRs show consistency in their shapes, but there remains a systematic offset and a moderate dispersion that cannot be explained by errors.  I will discuss possible explanations for this, including the effects of metallicity and rotation on stellar evolution and what challenges remain in the models.