Studies of non-adiabatic pulsations in the atmospheres of the roAp stars

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dc.contributor.advisorChristensen-Dalsgaard, Jen_ZA
dc.contributor.advisorKurtz, D Wen_ZA
dc.contributor.authorMedupe, Rodneyen_ZA
dc.date.accessioned2014-11-11T20:17:33Z
dc.date.available2014-11-11T20:17:33Z
dc.date.issued2002en_ZA
dc.descriptionIncludes bibliographical references.en_ZA
dc.description.abstractThe 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.en_ZA
dc.identifier.apacitationMedupe, R. (2002). <i>Studies of non-adiabatic pulsations in the atmospheres of the roAp stars</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Astronomy. Retrieved from http://hdl.handle.net/11427/9582en_ZA
dc.identifier.chicagocitationMedupe, Rodney. <i>"Studies of non-adiabatic pulsations in the atmospheres of the roAp stars."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Astronomy, 2002. http://hdl.handle.net/11427/9582en_ZA
dc.identifier.citationMedupe, R. 2002. Studies of non-adiabatic pulsations in the atmospheres of the roAp stars. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Medupe, Rodney AB - 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. DA - 2002 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2002 T1 - Studies of non-adiabatic pulsations in the atmospheres of the roAp stars TI - Studies of non-adiabatic pulsations in the atmospheres of the roAp stars UR - http://hdl.handle.net/11427/9582 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/9582
dc.identifier.vancouvercitationMedupe R. Studies of non-adiabatic pulsations in the atmospheres of the roAp stars. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Astronomy, 2002 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/9582en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Astronomyen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherScienceen_ZA
dc.titleStudies of non-adiabatic pulsations in the atmospheres of the roAp starsen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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