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Studies of non-adiabatic pulsations in the atmospheres of the roAp stars
Includes bibliographical references.
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| Main Author: | |
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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Department of Astronomy
2014
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| _version_ | 1867613174900981760 |
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| access_status_str | Open Access |
| author | Medupe, Rodney |
| author2 | Christensen-Dalsgaard, J |
| author_browse | Christensen-Dalsgaard, J Medupe, Rodney |
| author_facet | Christensen-Dalsgaard, J Medupe, Rodney |
| author_sort | Medupe, Rodney |
| collection | Thesis |
| description | Includes bibliographical references. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/9582 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:31:56.645Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2014 |
| publishDateRange | 2014 |
| publishDateSort | 2014 |
| publisher | Department of Astronomy |
| publisherStr | Department of Astronomy |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/9582 Studies of non-adiabatic pulsations in the atmospheres of the roAp stars Medupe, Rodney Christensen-Dalsgaard, J Kurtz, D W Science Includes bibliographical references. The roAp stars are high overtone pulsators characterised by strong global magnetic fields with effective field strength of between a few hundred to a few thousand Gauss. They also show overabundances in rare-earths and iron peak element. Multi-colour photometry of roAp stars shows that their pulsation amplitudes decrease more rapidly with increasing wavelength compared to other classically pulsating stars (e.g. Medupe & Kurtz 1998). In addition, this thesis shows that the pulsation phase can vary by up to 80° from Johnson U to V filters. In an attempt to explain the amplitude vs wavelength Kurtz & Medupe (1996) derived an analytic formula that indicated that the steep variation of the temperature eigenfunction with depth in the roAp atmospheres is the possible reason the rapid decrease of amplitude with wavelength. Even though Medupe & Kurtz (1998) showed that the analytical formula they derived in 1996 was a special form of a more general formula presented in Watson (1988), they found limitations in both formulae (see also Medupe, Christensen-Dalsgaard & Kurtz 1998 and chapter 3 of this thesis). This motivated me to attempt a numerical solution of the pulsation equations with consistent treatment of radiative transfer to investigate the multi-colour photometric data. In this thesis, we report on the multi-colour pulsation amplitudes and phases for HD 128898, HD 101065, HD 134214 and HD 137949. We also report on the campaign undertaken in 1996 and 1998 to determine whether the HR 3831 amplitude and phase vs wavelength changes with rotation. No variations with rotation are found. We find that the pulsation phase varies by up to about 80° from Johnson U to V in HD 101065 and HR 3831. 2014-11-11T20:17:33Z 2014-11-11T20:17:33Z 2002 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/9582 eng application/pdf Department of Astronomy Faculty of Science University of Cape Town |
| spellingShingle | Science Medupe, Rodney Studies of non-adiabatic pulsations in the atmospheres of the roAp stars |
| thesis_degree_str | Doctoral |
| title | Studies of non-adiabatic pulsations in the atmospheres of the roAp stars |
| title_full | Studies of non-adiabatic pulsations in the atmospheres of the roAp stars |
| title_fullStr | Studies of non-adiabatic pulsations in the atmospheres of the roAp stars |
| title_full_unstemmed | Studies of non-adiabatic pulsations in the atmospheres of the roAp stars |
| title_short | Studies of non-adiabatic pulsations in the atmospheres of the roAp stars |
| title_sort | studies of non adiabatic pulsations in the atmospheres of the roap stars |
| topic | Science |
| url | http://hdl.handle.net/11427/9582 |
| work_keys_str_mv | AT meduperodney studiesofnonadiabaticpulsationsintheatmospheresoftheroapstars |