Magnetic Fields of Degenerate Stars - Supervisor: Stefano Bagnulo
White dwarfs (WDs) are the end point of 90% of stellar evolution. 15–20% of such stars possess strong magnetic fields. The fields range over five dex in strength, from below ten kG (one Tesla) up to about 1000 MG. The fields are roughly dipolar, and show no evidence of rapid secular changes. They seem to be “fossil fields”, produced in earlier evolution that evolve slowly by ohmic decay. At present, there is no single firmly established theoretical scenario that explains how prior evolution through the red giant and AGB phases can leave strong surface fossil magnetic fields in a significant fraction of WDs. Possibilities include retaining fields from earlier evolutionary phases, or field generation during binary mergers.
Using various facilities at the Very Large Telescope, at the Canada-France-Hawaii Telescope, and at the William Heschel Telescope, Armagh astronomers are performing a large survey of magnetic WDs in the vicinity of our solar system, with the goal to understand if and how magnetic fields evolve with time, and if they are correlated to other features of the stellar atmospheric chemistry, mass, and age. A PhD project is offered to help to obtain observational constraints that will be used to understand the origin of magnetic fields in WDs.
The student will learn how to use spectro-polarimetric techniques to detected and model stellar magnetic fields. She or he will help with the preparation of proposal for telescope time, with the execution and analysis of the observations, with the search for correlation between magnetic fields and other stellar parameters, and with the modelling of time series of polarised spectra and of surface magnetic field structure of of WDs. The project will be more theoretically or observationally oriented according to the preference and skills of the student.
For further information contact firstname.lastname@example.org