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Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables
Doppler tomography has revolutionised the interpretation of phase-resolved spectra of interacting binaries. The standard technique extracts emission and kinematic information contained in such spectra and projects it onto a two-dimensional velocity coordinate frame. This thesis describes my investig...
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| Format: | Thesis |
| Language: | English |
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Department of Astronomy
2017
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| _version_ | 1867613185005060096 |
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| access_status_str | Open Access |
| author | Kotze, Enrico Juan |
| author2 | McBride, Vanessa A |
| author_browse | Kotze, Enrico Juan McBride, Vanessa A |
| author_facet | McBride, Vanessa A Kotze, Enrico Juan |
| author_sort | Kotze, Enrico Juan |
| collection | Thesis |
| description | Doppler tomography has revolutionised the interpretation of phase-resolved spectra of interacting binaries. The standard technique extracts emission and kinematic information contained in such spectra and projects it onto a two-dimensional velocity coordinate frame. This thesis describes my investigation of constructing Doppler tomograms in 'inside-out' coordinates by reversing the velocity axis. The aim was to determine if the emission distribution in the inside-out tomogram is more intuitive to interpret than the standard tomogram, and if it reveals indiscernible or enhances less discernible details. The inside-out tomogram is constructed by projecting the spectra onto the inside-out coordinate frame with zero velocity transposed to the outer circumference and the maximum velocities to the centre of the tomogram. In addition, this thesis describes a new flux modulation mapping technique applied to the standard and inside-out Doppler tomography of magnetic cataclysmic variables. I developed this technique with the aim to obtain more information from their observed spectra and present it in a useful format. It extracts the flux modulation from consecutive half-phase tomograms and constructs maps of the amplitude and phasing characteristics of the modulation in these systems. My investigation, involving the spectra of non-magnetic and magnetic cataclysmic variables, shows that the inside-out projection redistributes the relative contrast levels in and amongst the emission components. The inside-out projection exposes low-velocity emission details which are overly compacted and enhances high-velocity emission details which are overly tenuous in the standard projection. In addition, the flux modulation mapping technique gives a significant improvement in reproducing the input spectra adding more confidence in the interpretation of the modulation maps. Notable results were obtained for the polars where the blob-like low-velocity emission in their standard tomograms is more exposed in their inside-out tomograms, making it easier to distinguish between the ballistic and magnetic accretion flows that are evident in their trailed spectra. Also, for all the polars investigated the high-velocity magnetic accretion flows not seen in their standard tomograms are revealed in their inside-out tomograms. This extra information is extremely valuable to form a more complete picture of the emission components, broadening our knowledge of the accretion dynamics in these systems. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/25356 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:07.214Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2017 |
| publishDateRange | 2017 |
| publishDateSort | 2017 |
| 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:11427/25356 Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables Kotze, Enrico Juan McBride, Vanessa A Potter, Stephen B Astronomy Doppler tomography has revolutionised the interpretation of phase-resolved spectra of interacting binaries. The standard technique extracts emission and kinematic information contained in such spectra and projects it onto a two-dimensional velocity coordinate frame. This thesis describes my investigation of constructing Doppler tomograms in 'inside-out' coordinates by reversing the velocity axis. The aim was to determine if the emission distribution in the inside-out tomogram is more intuitive to interpret than the standard tomogram, and if it reveals indiscernible or enhances less discernible details. The inside-out tomogram is constructed by projecting the spectra onto the inside-out coordinate frame with zero velocity transposed to the outer circumference and the maximum velocities to the centre of the tomogram. In addition, this thesis describes a new flux modulation mapping technique applied to the standard and inside-out Doppler tomography of magnetic cataclysmic variables. I developed this technique with the aim to obtain more information from their observed spectra and present it in a useful format. It extracts the flux modulation from consecutive half-phase tomograms and constructs maps of the amplitude and phasing characteristics of the modulation in these systems. My investigation, involving the spectra of non-magnetic and magnetic cataclysmic variables, shows that the inside-out projection redistributes the relative contrast levels in and amongst the emission components. The inside-out projection exposes low-velocity emission details which are overly compacted and enhances high-velocity emission details which are overly tenuous in the standard projection. In addition, the flux modulation mapping technique gives a significant improvement in reproducing the input spectra adding more confidence in the interpretation of the modulation maps. Notable results were obtained for the polars where the blob-like low-velocity emission in their standard tomograms is more exposed in their inside-out tomograms, making it easier to distinguish between the ballistic and magnetic accretion flows that are evident in their trailed spectra. Also, for all the polars investigated the high-velocity magnetic accretion flows not seen in their standard tomograms are revealed in their inside-out tomograms. This extra information is extremely valuable to form a more complete picture of the emission components, broadening our knowledge of the accretion dynamics in these systems. 2017-09-23T06:38:09Z 2017-09-23T06:38:09Z 2017 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/25356 eng application/pdf Department of Astronomy Faculty of Science University of Cape Town |
| spellingShingle | Astronomy Kotze, Enrico Juan Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables |
| thesis_degree_str | Doctoral |
| title | Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables |
| title_full | Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables |
| title_fullStr | Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables |
| title_full_unstemmed | Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables |
| title_short | Transforming Doppler tomography to unravel the accretion dynamics in cataclysmic variables |
| title_sort | transforming doppler tomography to unravel the accretion dynamics in cataclysmic variables |
| topic | Astronomy |
| url | http://hdl.handle.net/11427/25356 |
| work_keys_str_mv | AT kotzeenricojuan transformingdopplertomographytounraveltheaccretiondynamicsincataclysmicvariables |