title: Constraints on the Origins of Magnetic White Dwarfs
creator: Külebi, Baybars
subject: 520
subject: 520 Astronomy and allied sciences
description: The central theme of this work is the most frequent final stage of the evolution of magnetic stars, the Magnetic White Dwarfs (MWDs). Improved statistical investigations coming from new surveys and very precise observations of unique MWDs  offer the possibility to test various hypotheses on the evolution of these objects.  In the first part of our work we identify hydrogen-rich MWDs  (DAHs) in the Sloan Digital Sky Survey (SDSS) and investigate the population statistics of all known DAHs in the SDSS. Additionally, we investigate the evolutionary histories of a few of these objects using constraints from the observations of their binary counterparts or through their membership in open clusters. In the second part of our work, we investigate the unique MWD REJ 0317-853, by a parallax measurement with the Hubble Space Telescope and by time resolved spectro-polarimetric modeling. We show that the assumption of centered magnetic dipoles for the field geometry is not correct for more than half of the objects in our sample; this is in particular true for REJ 0317-853 which shows a very uniform field during one rotation phase. This is validated by the first observation of cyclotron absorption in the  polarization spectrum of a white dwarf, which is explained with a new model for the self-consistent physical treatment of this absorption process. Furthermore, we study the possible influence of magnetism   on the mass loss during the stellar evolution and on the structure of the star which is of importance to understand the nature of the massive white dwarf REJ 0317-853.
date: 2010
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserverhttps://archiv.ub.uni-heidelberg.de/volltextserver/11477/1/bkulebi_th.pdf
identifier: DOI:10.11588/heidok.00011477
identifier: urn:nbn:de:bsz:16-opus-114772
identifier:   Külebi, Baybars  (2010) Constraints on the Origins of Magnetic White Dwarfs.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/11477/
rights: info:eu-repo/semantics/openAccess
rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html
language: eng