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Title: Mode identification in slowly pulsating subdwarf-B stars from line-profile variations
Author: Schoenaers, Caroline
ISNI:       0000 0001 3556 5077
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2007
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In previous attempts to perform seismic modelling of pulsating subdwarf-B stars, various mode identification techniques have been used, with less success than in pulsating Main Sequence stars. In this work I investigate a method so far neglected in sdB stars, that is, mode identification from the line-profile variations caused by stellar pulsation. I present the first detailed spectrum synthesis of pulsating subdwarf-B stars, taking into account variations, due to non-radial pulsations, in radial velocity, surface temperature, surface gravity and surface normal. Time-series of synthetic spectra demonstrate line-profile variations are to be expected in pulsating subdwarf-B stars. I then present the 'synthetic moment' method, an original spectroscopic mode identification method I designed, and test it extensively on synthetic line-profile variations representative of those observed in slowly pulsating subdwarf-B stars. The 'synthetic moment' method is applied to spectroscopic data of slowly pulsating subdwarf-B stars HD 4539, EC 21324-1346 and PG 1627+017 I obtained at the South African Astronomical Observatory. For each of these stars I identify several pulsation modes, which in turn allows me to select their possible evolutionary stages. My pioneering work on spectroscopic mode identification in slowly pulsating subdwarf-B star sets the stage for a thorough analysis of all known sdB pulsators, thereby making for a better understanding of this late stage of stellar evolution.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available