Title

Determination of the Initial–Final Mass Relation for White Dwarfs with Helium Atmospheres

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Physics and Astronomy

Date of Award

Fall 2020

Abstract

White dwarfs are the final stage of stellar evolution for over 95% of stars. White dwarfsare classified into spectral types based on atmospheric composition. In particular, DA white dwarfs have hydrogen atmospheres, while DB white dwarfs have helium atmospheres. The initial-final mass relation relates the mass of a white dwarf to the mass of the progenitor star. The initial–final mass relation for DA white dwarfs is well understood and has been studied extensively. In contrast, DB white dwarf masses are harder to measure accurately and are thus only recently suitable for initial-final mass relation work. In this study we seek to construct a semi–empirical initial–final mass relation for DB white dwarfs. To accomplish this, we start by defining a sample of open cluster DB white dwarfs for which there are good spectra. In our case we had 8 white dwarfs in our sample. Next, we collect available astrometry and photometry data for each white dwarf in the sample. Collaborating with a research group at the University of Montreal we obtain temperatures and surface gravities for each DB white dwarf. Finally, with these data and adapted software we obtain the initial and final masses of the white dwarfs and construct the DB semi–empirical initial–final mass relation. Of our eight white dwarfs, only six of them had reasonable initial and final masses. The initial-final mass relation for DB white dwarfs appears to be lower than the best 3-piece fit for the initial-final mass relation for DA white dwarfs. However, data are still sparse and uncertainties in cluster membership and atmosphere abundances remain. Further spectroscopic and photometric analyses will be necessary to overcome these uncertainties.

Advisor

Kurtis A. Williams

Subject Categories

Astrophysics and Astronomy | Physical Sciences and Mathematics

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