Magnetic Fields and Accretion Processes in Young Stars: A case study of the classical T Tauri star DK Tau
APPROVED Low-mass young stars that are a few million years old and called classical T Tauri stars (cTTs) experience magnetospheric accretion. They are surrounded by a circumstellar disk (which consists of an inner and outer disk) and accrete matter from it thanks to their magnetic fields. When the m...
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| Other Authors: | , |
| Format: | Doctoral or Postdoctoral Thesis |
| Language: | unknown |
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Trinity College Dublin. School of Physics. Discipline of Physics
2024
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| Online Access: | http://hdl.handle.net/2262/106605 https://tcdlocalportal.tcd.ie/pls/EnterApex/f?p=800:71:0::::P71_USERNAME:NELISSEM |
| Summary: | APPROVED Low-mass young stars that are a few million years old and called classical T Tauri stars (cTTs) experience magnetospheric accretion. They are surrounded by a circumstellar disk (which consists of an inner and outer disk) and accrete matter from it thanks to their magnetic fields. When the matter falls onto the star, it produces an accretion shock, which generates veiling in the stellar spectra. The shock also causes an accretion spot on the stellar surface. Misalignments between the stellar rotation axis and the outer disk axis are not predicted by standard theories of stellar formation, yet have been observed in several cTTs. This thesis studies one cTTs in particular, DK Tau, which is suspected of being among them. Additionally, it is an excellent subject to investigate the interaction between stellar magnetic fields and material accreting from the circumstellar disk, since it displays clear signatures of accretion. Focusing on a single object allows one to uncover the physics that governs its behavior, and the values derived from its analysis are important to constrain the models of star formation. One goal of this thesis is to study DK Tau's average line-of-sight magnetic field in both photospheric absorption lines and accretion-powered emission lines. The second is to examine inconsistencies regarding the inclination of its rotation axis. The third aim is to investigate the accretion, particularly the mass accretion rate, using two different methods for comparison purposes. The last objective is to carry out a preliminary study of its large-scale magnetic field configuration. For these purposes, archival data from the CFHT/ESPaDOnS and TBL/NARVAL spectropolarimeters were used. The observations probe two distinct epochs (i.e. 2010 and 2012), allowing one to study the evolution of DK Tau over time. Each dataset spans a few stellar rotation cycles and covers the optical range. First, stellar parameters were determined. Next, the veiling was measured across the spectra and its effects were removed. ... |
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