subject:(Stellar Winds )

Queens University

1. David-Uraz, Alexandre. Investigating the potential magnetic origin of wind variability in OB stars .

Degree: Physics, Engineering Physics and Astronomy, 2016, Queens University

URL: http://hdl.handle.net/1974/14445

► In this thesis, the origin of large-scale structures in hot star winds, believed to be responsible for the presence of discrete absorption components (DACs) in… (more)

▼ In this thesis, the origin of large-scale structures in hot star winds, believed to be responsible for the presence of discrete absorption components (DACs) in the absorption troughs of ultraviolet resonance lines, is constrained using both observations and numerical simulations. These structures are understood as arising from bright regions on the stellar surface, although their physical cause remains unknown. First, we use high quality circular spectropolarimetric observations of 13 well-studied OB stars to evaluate the potential role of dipolar magnetic fields in producing DACs. We perform longitudinal field measurements and place limits on the field strength using Bayesian inference, assuming that it is dipolar. No magnetic field was detected within this sample. The derived constraints statistically refute any significant dynamical influence from a magnetic dipole on the wind for all of these stars, ruling out such fields as a cause for DACs. Second, we perform numerical simulations using bright spots constrained by broadband optical photometric observations. We calculate hydrodynamical wind models using three sets of spot sizes and strengths. Co-rotating interaction regions are yielded in each model, and radiative transfer shows that the properties of the variations in the UV resonance lines synthesized from these models are consistent with those found in observed UV spectra, establishing the first consistent link between UV spectroscopic line profile variability and photometric variations and thus supporting the bright spot paradigm (BSP). Finally, we develop and apply a phenomenological model to quantify the measurable effects co-rotating bright spots would have on broadband optical photometry and on the profiles of photopheric lines in optical spectra. This model can be used to evaluate the existence of these spots, and, in the event of their detection, characterize them. Furthermore, a tentative spot evolution model is presented. A preliminary analysis of its output, compared to the observed photometric variations of xi Persei, suggests the possible existence of “active longitudes” on the surface of this star. Future work will expand the range of observational diagnostics that can be interpreted within the BSP, and link phenomenology (bright spots) to physical processes (magnetic spots or non-radial pulsations).

Subjects/Keywords: astrophysics ; stellar winds ; massive stars

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APA (6^th Edition):

David-Uraz, A. (2016). Investigating the potential magnetic origin of wind variability in OB stars . (Thesis). Queens University. Retrieved from http://hdl.handle.net/1974/14445

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

David-Uraz, Alexandre. “Investigating the potential magnetic origin of wind variability in OB stars .” 2016. Thesis, Queens University. Accessed March 07, 2021. http://hdl.handle.net/1974/14445.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

David-Uraz, Alexandre. “Investigating the potential magnetic origin of wind variability in OB stars .” 2016. Web. 07 Mar 2021.

Vancouver:

David-Uraz A. Investigating the potential magnetic origin of wind variability in OB stars . [Internet] [Thesis]. Queens University; 2016. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/1974/14445.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

David-Uraz A. Investigating the potential magnetic origin of wind variability in OB stars . [Thesis]. Queens University; 2016. Available from: http://hdl.handle.net/1974/14445

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Queens University

2. Shultz, Matthew. The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars .

Degree: Physics, Engineering Physics and Astronomy, 2016, Queens University

URL: http://hdl.handle.net/1974/14691

► How do the magnetic fields of massive stars evolve over time? Are their gyrochronological ages consistent with ages inferred from evolutionary tracks? Why do most… (more)

▼ How do the magnetic fields of massive stars evolve over time? Are their gyrochronological ages consistent with ages inferred from evolutionary tracks? Why do most stars predicted to host Centrifugal Magnetospheres (CMs) display no Hα emission? Does plasma escape from CMs via centrifugal breakout events, or by a steady-state leakage mechanism? This thesis investigates these questions via a population study with a sample of 51 magnetic early B-type stars. The longitudinal magnetic field \bz~was measured from Least Squares Deconvolution profiles extracted from high-resolution spectropolarimetric data. New rotational periods P_rot were determined for 15 stars from \bz, leaving only 3 stars for which P_rot is unknown. Projected rotational velocities \vsini~were measured from multiple spectral lines. Effective temperatures and surface gravities were measured via ionization balances and line profile fitting of H Balmer lines. Fundamental physical parameters, \bz, \vsini, and P_rot were then used to determine radii, masses, ages, dipole oblique rotator model, stellar wind, magnetospheric, and spindown parameters using a Monte Carlo approach that self-consistently calculates all parameters while accounting for all available constraints on stellar properties. Dipole magnetic field strengths B_d follow a log-normal distribution similar to that of Ap stars, and decline over time in a fashion consistent with the expected conservation of fossil magnetic flux. P_rot increases with fractional main sequence age, mass, and B_d, as expected from magnetospheric braking. However, comparison of evolutionary track ages to maximum spindown ages t_S,max shows that initial rotation fractions may be far below critical for stars with M_*>10 M_\odot. Computing t_S,max with different mass-loss prescriptions indicates that the mass-loss rates of B-type stars are likely much lower than expected from extrapolation from O-type stars. Stars with Hα in emission and absorption occupy distinct regions in the updated rotation-magnetic confinement diagram: Hα-bright stars are found to be younger, more rapidly rotating, and more strongly magnetized than the general population. Emission strength is sensitive both to the volume of the CM and to the mass-loss rate, favouring leakage over centrifugal breakout.

Subjects/Keywords: Stellar Winds ; Binary Stars ; Magnetospheres ; Massive Stars ; Magnetic Braking ; Stellar Magnetism ; Spectropolarimetry

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APA (6^th Edition):

Shultz, M. (2016). The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars . (Thesis). Queens University. Retrieved from http://hdl.handle.net/1974/14691

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Shultz, Matthew. “The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars .” 2016. Thesis, Queens University. Accessed March 07, 2021. http://hdl.handle.net/1974/14691.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Shultz, Matthew. “The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars .” 2016. Web. 07 Mar 2021.

Vancouver:

Shultz M. The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars . [Internet] [Thesis]. Queens University; 2016. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/1974/14691.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Shultz M. The Rotational Evolution and Magnetospheric Emission of the Magnetic Early B-type Stars . [Thesis]. Queens University; 2016. Available from: http://hdl.handle.net/1974/14691

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Delaware

3. Kee, Nathaniel Dylan. Radiative ablation of disks around massive stars.

Degree: PhD, University of Delaware, Department of Physics and Astronomy, 2015, University of Delaware

URL: http://udspace.udel.edu/handle/19716/17601

► Hot, massive stars (spectral types O and B) have extreme luminosities (104 − 106L ) that drive strong stellar winds through UV line-scattering. Some massive… (more)

▼ Hot, massive stars (spectral types O and B) have extreme luminosities (104 − 106L ) that drive strong stellar winds through UV line-scattering. Some massive stars also have disks, formed by either decretion from the star (as in the rapidly rotating “Classical Be stars”), or accretion during the star’s formation. Extending the winddeveloped Sobolev methods for line radiative transfer, this dissertation examines the role of stellar radiation in driving (ablating) material away from these circumstellar disks. A key result is that the observed month to year decay of optically thin Be disks can be explained by line-driven ablation without, as was done in previous work, appealing to anomalously strong viscous diffusion. Moreover, the higher luminosity of O stars leads to ablation of optically thin disks on dynamical timescales of order a day, providing a natural explanation for the lack of observed Oe stars. In addition to the destruction of Be disks, this dissertation also introduces a model for their formation via “Pulsationally Driven Orbital Mass Ejection”. This “PDOME” model couples observationally inferred non-radial pulsation modes and rapid stellar rotation to launch material into orbiting Keplerian disks of Be-like densities. In contrast to such Be decretion disks, star-forming accretion disks are much denser and so are generally optically thick to continuum processes like electron scattering. To circumvent the computational challenges associated with long-characteristic radiation hydrodynamics through optically thick media, we develop an approximate method for treating optically thick continuum absorption in the limit of geometrically thin disks. The comparison of ablation with and without continuum absorption shows that accounting for disk optical thickness leads to less than a 50% reduction in ablation rate, implying that ablation rate is largely independent of disk mass, and depends mainly on stellar properties like luminosity. Finally, as a side problem, we discuss the role of “thin-shell mixing” in reducing X-rays from colliding wind binaries. Laminar, adiabatic shocks produce well understood X-ray emission, but the emission from radiatively cooled shocks is more complex due to thin-shell instabilities. The parameter study conducted here systematically varies colliding wind binary shock densities to determine scaling relations for this emission. A key result is that, in the limit of strongly radiatively cooled shocks, emission is reduced by a fixed factor ∼ 50 from analytic scalings that ignore thin-shell structure. Advisors/Committee Members: Owocki, Stanley.

Subjects/Keywords: Stars – Radiation.; Disks (Astrophysics); X-rays.; Stellar winds.

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APA (6^th Edition):

Kee, N. D. (2015). Radiative ablation of disks around massive stars. (Doctoral Dissertation). University of Delaware. Retrieved from http://udspace.udel.edu/handle/19716/17601

Chicago Manual of Style (16^th Edition):

Kee, Nathaniel Dylan. “Radiative ablation of disks around massive stars.” 2015. Doctoral Dissertation, University of Delaware. Accessed March 07, 2021. http://udspace.udel.edu/handle/19716/17601.

MLA Handbook (7^th Edition):

Kee, Nathaniel Dylan. “Radiative ablation of disks around massive stars.” 2015. Web. 07 Mar 2021.

Vancouver:

Kee ND. Radiative ablation of disks around massive stars. [Internet] [Doctoral dissertation]. University of Delaware; 2015. [cited 2021 Mar 07]. Available from: http://udspace.udel.edu/handle/19716/17601.

Council of Science Editors:

Kee ND. Radiative ablation of disks around massive stars. [Doctoral Dissertation]. University of Delaware; 2015. Available from: http://udspace.udel.edu/handle/19716/17601

Queens University

4. Shultz, Matthew Eric. Magnetic fields and the variable wind of the early-type supergiant β Ori .

Degree: Physics, Engineering Physics and Astronomy, 2012, Queens University

URL: http://hdl.handle.net/1974/7165

► Supergiant stars of spectral types B and A are characterized by variable and structured winds, as revealed by variability of optical and ultraviolet spectral lines.… (more)

▼ Supergiant stars of spectral types B and A are characterized by variable and structured winds, as revealed by variability of optical and ultraviolet spectral lines. Non- radial pulsations and magnetically supported loops have been proposed as explanations for these phenomena. The latter hypothesis is tested using a time series of 65 high-resolution (λ/∆λ ∼ 65, 000) circular polarization (Stokes I and V ) spectra of the late B type supergiant Rigel (β Ori, B8 Iae), obtained with the instruments ESPaDOnS and Narval at the Canada-France-Hawaii Telescope and the Bernard Lyot Telescope, respectively. Examination of the unpolarized (Stokes I) spectra using standard spectral analysis tools confirms complex line profile variability during the 5 month period of observations; the high spectral resolution allows the identification of a weak, transient Hα feature similar in behaviour to a High Velocity Absorption event. Analysis of the Stokes V spectra using the cross-correlation technique Least Squares Deconvolution (LSD) yields no evidence of a magnetic field in either LSD Stokes V profiles or longitudinal field measurements, with longitudinal field 1σ error bars of ∼ 12 G for individual observations, and a mean field in the best observed period of 3 ± 2 G. Synthetic LSD profiles fit to the observations using a Monte Carlo approach yield an upper limit on the surface dipolar field strength of Bdip ≤ 50 G for most orientations of the rotational and magnetic axes, lowered to Bdip ≤ 35 G if the mean LSD profile from the most densely time-sampled epoch (with an LSD SNR of ∼80,000) is used. A simple two-spot geometry representing the footpoints of a magnetic loop emerging from the photosphere yields upper limits on the spot magnetic fields of 60–600 G, depending on the filling factor of the spots. Given existing measurements of the mass loss rate and the wind terminal velocity, these results cannot rule out a magnetically confined wind as, for Bdip ≤ 15 G, η∗ ≥ 1. However, the detailed pattern of line profile variability seems inconsistent with the periodic wind modulation characteristic of known magnetic early-type stars, suggesting that magnetic fields do not play a dominant role in Rigel’s variable winds.

Subjects/Keywords: stellar winds ; Stars (magnetic) ; stars (early type) ; stars (supergiant) ; spectropolarimetry

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Shultz, M. E. (2012). Magnetic fields and the variable wind of the early-type supergiant β Ori . (Thesis). Queens University. Retrieved from http://hdl.handle.net/1974/7165

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Shultz, Matthew Eric. “Magnetic fields and the variable wind of the early-type supergiant β Ori .” 2012. Thesis, Queens University. Accessed March 07, 2021. http://hdl.handle.net/1974/7165.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Shultz, Matthew Eric. “Magnetic fields and the variable wind of the early-type supergiant β Ori .” 2012. Web. 07 Mar 2021.

Vancouver:

Shultz ME. Magnetic fields and the variable wind of the early-type supergiant β Ori . [Internet] [Thesis]. Queens University; 2012. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/1974/7165.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Shultz ME. Magnetic fields and the variable wind of the early-type supergiant β Ori . [Thesis]. Queens University; 2012. Available from: http://hdl.handle.net/1974/7165

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

5. Puebla, Raul Eduardo Puebla. Síntese espectral detalhada de discos de acrescão com vento.

Degree: PhD, Astronomia, 2010, University of São Paulo

URL: http://www.teses.usp.br/teses/disponiveis/14/14131/tde-28092010-152003/ ;

►

Neste trabalho foi desenvolvido um novo m´etodo de s´ntese espectral para modelar o disco de acres¸cao de vari´aveis catacl´smicas (VCs) nao magn´eticas. O principal objetivo… (more)

▼

Neste trabalho foi desenvolvido um novo m´etodo de s´ntese espectral para modelar o disco de acres¸cao de vari´aveis catacl´smicas (VCs) nao magn´eticas. O principal objetivo deste trabalho ´e analisar a emissao do cont´nuo e das linhas em uma ampla faixa espectral no ultravioleta (UV). O disco ´e separado em an´eis concentricos e, para cada anel uma atmosfera de disco com vento ´e calculada. Na base, as atmosferas sao calculadas consistemente com o vento, tendo a distribui¸cao de densidade dos modelos de atmosferas de disco de Wade e Hubeny. A estrutura ´e calculada no sistema co-m´ovel com um perfil de velocidade vertical obtido da solu¸cao da equa¸cao de Euler para um disco de acres¸cao. O comportamento das linhas e do cont´nuo como fun¸cao da inclina¸cao orbital ´e consistente com as observa¸coes. Tamb´em foi verificado que a taxa de acres¸cao influi sobre a temperatura do vento levando `as mudan¸cas correspondentes nas intensidades relativas das linhas. Foi encontrado que a massa da prim´aria tem uma forte influencia na profundidade dos perfis de absor¸cao. Tamb´em, encontramos que a os perfis de linha sao fortemente sens´veis ao incremento da taxa de perda de massa, aumentado a intensidade das linhas de emissao. Foram escolhidos dados espectrosc´opicos no UV de duas VCs Nova-like (NL) de baixa inclina¸cao, RW Sex e V3885 Sgr e dois sistemas de alta inclina¸cao, RW Tri e V347 Pup. Uma concordancia dos perfis em emissao dos modelos foi encontrada quando confrontados com os dados no caso de sistemas de alta inclina¸cao. Uma falta de fluxo nas linhas de alta ioniza¸cao Civ ¸¸1548,1551 and Nv ¸¸1238,1242, pode ser o sinal da influencia da boundary layer (BL) ou da influencia da irradia¸cao das regioes externas do vento pelo disco interno. Estas influencias seriam cruciais no caso de sistemas baixa inclina¸cao, mas sao menores no caso de sistemas de alta inclina¸cao.

We have developed a new spectral synthesis method for modeling the accretion disk of non-magnetic cataclysmic variables (CVs). The aim of this work is to analyze the continuum and line emission of disks in a wide ultraviolet (UV) spectral range. The disk is separated in concentric rings, and for each ring a wind plus disk atmosphere are calculated. The wind atmospheres are calculated consistently with a density given by Wade and Hubeny disk-atmosphere models at their base. The structure is calculated in the co-moving frame with a vertical velocity profile defined by the Eulers equation solution for the disk wind. We found that the resulting line and continuum behavior as a function of the orbital inclination is consistent with the observations. We also verify that the accretion rate changes the wind temperature, leading to corresponding trends in the intensity of lines. We found that the primary mass has a strong effect on the absorption profiles depth. It was verified that the lines profiles are strongly sensitive to the wind temperature structure and a rise of mass loss rate increases the line intensity. Selected UV data for two high orbital…

Advisors/Committee Members: Diaz, Marcos Perez.

Subjects/Keywords: Accretions Disk; Cataclysmic Variables; Discos de Acresção; Stellar Winds; Variáveis Cataclísmicas; Ventos Estelares

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APA (6^th Edition):

Puebla, R. E. P. (2010). Síntese espectral detalhada de discos de acrescão com vento. (Doctoral Dissertation). University of São Paulo. Retrieved from http://www.teses.usp.br/teses/disponiveis/14/14131/tde-28092010-152003/ ;

Chicago Manual of Style (16^th Edition):

Puebla, Raul Eduardo Puebla. “Síntese espectral detalhada de discos de acrescão com vento.” 2010. Doctoral Dissertation, University of São Paulo. Accessed March 07, 2021. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-28092010-152003/ ;.

MLA Handbook (7^th Edition):

Puebla, Raul Eduardo Puebla. “Síntese espectral detalhada de discos de acrescão com vento.” 2010. Web. 07 Mar 2021.

Vancouver:

Puebla REP. Síntese espectral detalhada de discos de acrescão com vento. [Internet] [Doctoral dissertation]. University of São Paulo; 2010. [cited 2021 Mar 07]. Available from: http://www.teses.usp.br/teses/disponiveis/14/14131/tde-28092010-152003/ ;.

Council of Science Editors:

Puebla REP. Síntese espectral detalhada de discos de acrescão com vento. [Doctoral Dissertation]. University of São Paulo; 2010. Available from: http://www.teses.usp.br/teses/disponiveis/14/14131/tde-28092010-152003/ ;

Rice University

6. Cauley, Paul Wilson. Diagnosing Mass Flows Around Herbig Ae/Be Stars.

Degree: PhD, Natural Sciences, 2014, Rice University

URL: http://hdl.handle.net/1911/87727

► Most stars form surrounded by a massive disk of dust and gas. As the star evolves, its interaction with the surrounding disk material has a… (more)

▼ Most stars form surrounded by a massive disk of dust and gas. As the star evolves, its interaction with the surrounding disk material has a significant impact on both the final evolutionary state of the star and the amount of material that is available in the disk to form planets, organic compounds, and, ultimately, life. Herbig Ae/Be stars (HAEBES) are recently formed intermediate mass (2-10 solar masses) pre – main sequence stars. Over 150 candidate HAEBES have been identified by various surveys. Although this number is large, it is relatively small compared to the number of identified classical T Tauri stars (CTTSs), the low mass (~1 solar mass) cousins of HAEBES. Although it is well established that both CTTSs and HAEBES are still evolving towards the main sequence, our understanding of how accretion and outflows operate around HAEBES compared to CTTSs is incomplete and there remains debate over the key launching mechanisms for the outflows in CTTSs. This is in large part due to the lack of comparisons of multi-wavelength mass flow diagnostics in large samples of HAEBES and CTTSs. In this thesis we attempt to address the gap in our knowledge of the driving mechanisms of accretion and outflows around HAEBES, and how they compare to those of CTTSs, by examining a wide variety of accretion and outflow diagnostics in the ultraviolet, optical, and near infrared with the goal of constraining the incidence of accretion and wind flows around these objects. A different incidence of accretion and outflow detections in HAEBES compared to CTTSs would indicate that the mechanisms governing the production of these flows in HAEBES differ from those in CTTSs and we can look to other key differences between these classes of stars to try to identify the mechanisms that control the flows. To accomplish this we analyze high resolution line profiles of a large number of spectral lines that are known to be good tracers of accretion and outflows around CTTSs. Our analysis reveals a significant difference between the occurrence of blue and red-shifted absorption features in HAEBES compared to CTTSs. This difference is largest for outflow signatures in the optical and is less significant in He I 10830, the near-IR diagnostic. We find that the incidence of red and blue-shifted absorption in HAEBES increases from the optical to the UV with intermediate rates being found in He I 10830. This suggests that hot (~100,000 K) mass flows are more common around HAEBES than cooler (~10,000 K) flows. We also find significant differences between the occurrence of red and blue – shifted absorption in HAe stars compared to HBe stars. In particular, our results support the idea of mangetospheric accretion occurring in HAe stars but provide more evidence for boundary layer accretion in HBe objects. In addition, we observe that the maximum red – shifted absorption velocities tracing infalling material in our sample are smaller fractions of the stellar escape velocity than is found for CTTSs. This is confirmed in both the optical diagnostics and at He I… Advisors/Committee Members: Johns-Krull, Christopher M (advisor), Hartigan, Patrick M (committee member), Gustin, Michael (committee member).

Subjects/Keywords: Pre-main sequence stars; Herbig Ae/Be stars/ Classical T Tauri stars; accretion; stellar winds

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APA (6^th Edition):

Cauley, P. W. (2014). Diagnosing Mass Flows Around Herbig Ae/Be Stars. (Doctoral Dissertation). Rice University. Retrieved from http://hdl.handle.net/1911/87727

Chicago Manual of Style (16^th Edition):

Cauley, Paul Wilson. “Diagnosing Mass Flows Around Herbig Ae/Be Stars.” 2014. Doctoral Dissertation, Rice University. Accessed March 07, 2021. http://hdl.handle.net/1911/87727.

MLA Handbook (7^th Edition):

Cauley, Paul Wilson. “Diagnosing Mass Flows Around Herbig Ae/Be Stars.” 2014. Web. 07 Mar 2021.

Vancouver:

Cauley PW. Diagnosing Mass Flows Around Herbig Ae/Be Stars. [Internet] [Doctoral dissertation]. Rice University; 2014. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/1911/87727.

Council of Science Editors:

Cauley PW. Diagnosing Mass Flows Around Herbig Ae/Be Stars. [Doctoral Dissertation]. Rice University; 2014. Available from: http://hdl.handle.net/1911/87727

University of Texas – Austin

7. Tsang, Tsz Ho. Monte Carlo radiation hydrodynamics in the super-Eddington regime.

Degree: PhD, Astronomy, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/69240

► In this dissertation, we present three projects addressing the dynamical importance of radiation in turbulent media with super-Eddington flux. Examples of such media are massive… (more)

▼ In this dissertation, we present three projects addressing the dynamical importance of radiation in turbulent media with super-Eddington flux. Examples of such media are massive star-forming environments and supermassive star atmospheres. While there are many theoretical models claiming the pivotal role of radiation in driving strong outflows and setting the star formation efficiency in the course of massive star formation, often they are based on ideal geometries and closure relations of the moment equations for radiation. To directly tackle the challenge of numerically modeling radiation-matter interactions in hydrodynamical simulations, we have adopted and tested a hybrid Monte Carlo radiation transport scheme. In the first project, with a standardized two-dimensional radiation-driven winds setup, we show that low-order methods tend to artificially reinforce the development of the low-density channels and underestimate the strength of radiation pressure. The accuracy of any numerical radiation transport scheme in producing truthful dynamics therefore depends on the validity of its underlying assumptions. In the second project, we carry out radiation hydrodynamical simulations of the formation of super star clusters in supersonically turbulent molecular clouds. The gas distribution is strongly inhomogeneous and that reduces the strength of radiation pressure in halting gas accretion compared to previous predictions. In the last project, unlike the inflow-outflow scenario of the first two, we aim to simulate the radiation hydrodynamics in quasi-hydrostatic media with extreme sensitivity of the opacity to density and temperature. We present the implementation and robustness test of the hybrid Monte Carlo estimators in preparation for direct simulations of the convective, radiation-dominated dynamics prevalent in the atmospheres of supermassive stars. Advisors/Committee Members: Milosavljević, Miloš (advisor), Bromm, Volker (committee member), Jogee, Shardha (committee member), Evans, Neal J. (committee member), Davis, Shane (committee member).

Subjects/Keywords: Star formation; Stellar atmosphere; Radiation-driven winds; Radiation hydrodynamics; Numerical methods; Radiative transfer

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APA (6^th Edition):

Tsang, T. H. (2018). Monte Carlo radiation hydrodynamics in the super-Eddington regime. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/69240

Chicago Manual of Style (16^th Edition):

Tsang, Tsz Ho. “Monte Carlo radiation hydrodynamics in the super-Eddington regime.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed March 07, 2021. http://hdl.handle.net/2152/69240.

MLA Handbook (7^th Edition):

Tsang, Tsz Ho. “Monte Carlo radiation hydrodynamics in the super-Eddington regime.” 2018. Web. 07 Mar 2021.

Vancouver:

Tsang TH. Monte Carlo radiation hydrodynamics in the super-Eddington regime. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/2152/69240.

Council of Science Editors:

Tsang TH. Monte Carlo radiation hydrodynamics in the super-Eddington regime. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/69240

University of Exeter

8. Finley, A. Constraining the angular momentum-loss rates of the Sun and other Sun-like stars.

Degree: PhD, 2020, University of Exeter

URL: http://hdl.handle.net/10871/121115

► Stellar rotation, convection, and magnetism are intricately linked in low-mass stars like the Sun. In their outer convective envelopes, the interplay of rotation and convection… (more)

Subjects/Keywords: solar wind; stellar winds; astrophysics; magnetohydrodynamics; numerical simulation; rotation period evolution; low-mass stars; sun-like stars

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APA (6^th Edition):

Finley, A. (2020). Constraining the angular momentum-loss rates of the Sun and other Sun-like stars. (Doctoral Dissertation). University of Exeter. Retrieved from http://hdl.handle.net/10871/121115

Chicago Manual of Style (16^th Edition):

Finley, A. “Constraining the angular momentum-loss rates of the Sun and other Sun-like stars.” 2020. Doctoral Dissertation, University of Exeter. Accessed March 07, 2021. http://hdl.handle.net/10871/121115.

MLA Handbook (7^th Edition):

Finley, A. “Constraining the angular momentum-loss rates of the Sun and other Sun-like stars.” 2020. Web. 07 Mar 2021.

Vancouver:

Finley A. Constraining the angular momentum-loss rates of the Sun and other Sun-like stars. [Internet] [Doctoral dissertation]. University of Exeter; 2020. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/10871/121115.

Council of Science Editors:

Finley A. Constraining the angular momentum-loss rates of the Sun and other Sun-like stars. [Doctoral Dissertation]. University of Exeter; 2020. Available from: http://hdl.handle.net/10871/121115

Université de Grenoble

9. Lamberts-Marcade, Astrid. Simulations numériques de collisions de vents dans les systèmes binaires : Numerical simulations of colliding winds in binary systems.

Degree: Docteur es, Astrophysique et milieux dilues, 2012, Université de Grenoble

URL: http://www.theses.fr/2012GRENY038

►

L'objectif de cette thèse est de comprendre la structure des binaires gamma, binaires à collision de vents composées d'une étoile massive et d'un pulsar jeune.… (more)

▼

L'objectif de cette thèse est de comprendre la structure des binaires gamma, binaires à collision de vents composées d'une étoile massive et d'un pulsar jeune. Ces binaires possèdent probablement une structure similaire aux binaires à collision de vents composées de deux étoiles massives, avec des particularités liées à la nature relativiste du vent de pulsar. L'interaction de deux vents supersoniques d'étoiles massives crée une structure choquée qui présente des signatures observationnelles du domaine radio aux rayons X. Plusieurs instabilités ainsi que le mouvement orbital des étoiles influent sur la structure choquée. Afin de comprendre leur impact, j'ai effectué des simulations à haute résolution de binaires à collision de vents à l'aide du code hydrodynamique RAMSES. Ces simulations sont numériquement coûteuses à réaliser, surtout lorsque un des vents domine fortement l'autre. A petite échelle, les simulations soulignent l'importance de l'instabilité de couche mince non-linéaire dans les collisions isothermes alors que l'instabilité de Kelvin-Helmholtz peut fortement modifier la structure choquée dans une collision adiabatique. A plus grande échelle, cette instabilité peut parfois détruire la structure spirale à laquelle on s'attend si la différence de vitesse entre les vents est trop importante. WR 104 est une binaire dont on observe la structure spirale grâce à l'émission de poussières. Les simulations de ce système montrent un bon accord avec la structure observée et indiquent que des processus de refroidissement du gaz sont nécessaires à la formation de poussières. Pour modéliser les vents de pulsar dans les binaires gamma, RAMSES a été étendu à l'hydrodynamique relativiste. J'utilise ce nouveau code pour réaliser des simulations préliminaires de binaires gamma. Elles montrent effectivement une structure similaire aux binaires stellaires, avec de légères corrections relativistes . Ce code est adapté à l'étude de divers systèmes astrophysiques tels que les jets relativistes, les sursauts gamma ou les nébuleuses de pulsar et fera partie de la prochaine version de RAMSES qui sera rendue publique.

The aim of this thesis is to understand the structure of colliding wind binaries composed of a massive star and a young pulsar, called gamma-ray binaries. They are expected to display a similar structure to colliding wind binaries composed of massive stars, with some particularities due to the relativistic nature of the pulsar wind. The interaction of the supersonic winds from massive stars creates a shocked structure with observational signatures from the radio domain to the X-rays. The structure is affected by various instabilities and by the orbital motion of the stars. To understand their impact, I carried out high resolution simulations of colliding wind binaries with the hydrodynamical code RAMSES. They are computationally demanding, especially when one of the winds strongly dominates the other one. Small scale simulations highlight the importance of the Non-linear Thin Shell Instability in isothermal…

Advisors/Committee Members: Dubus, Guillaume (thesis director).

Subjects/Keywords: Simulations hydrodynamiques; Vents stellaires; Systèmes binaires; Instabilités; Hydrodynamical simulations; Stellar winds; Binary systems; Instabilities; Numerical relativity; Gamma-ray binaries

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Lamberts-Marcade, A. (2012). Simulations numériques de collisions de vents dans les systèmes binaires : Numerical simulations of colliding winds in binary systems. (Doctoral Dissertation). Université de Grenoble. Retrieved from http://www.theses.fr/2012GRENY038

Chicago Manual of Style (16^th Edition):

Lamberts-Marcade, Astrid. “Simulations numériques de collisions de vents dans les systèmes binaires : Numerical simulations of colliding winds in binary systems.” 2012. Doctoral Dissertation, Université de Grenoble. Accessed March 07, 2021. http://www.theses.fr/2012GRENY038.

MLA Handbook (7^th Edition):

Lamberts-Marcade, Astrid. “Simulations numériques de collisions de vents dans les systèmes binaires : Numerical simulations of colliding winds in binary systems.” 2012. Web. 07 Mar 2021.

Vancouver:

Lamberts-Marcade A. Simulations numériques de collisions de vents dans les systèmes binaires : Numerical simulations of colliding winds in binary systems. [Internet] [Doctoral dissertation]. Université de Grenoble; 2012. [cited 2021 Mar 07]. Available from: http://www.theses.fr/2012GRENY038.

Council of Science Editors:

Lamberts-Marcade A. Simulations numériques de collisions de vents dans les systèmes binaires : Numerical simulations of colliding winds in binary systems. [Doctoral Dissertation]. Université de Grenoble; 2012. Available from: http://www.theses.fr/2012GRENY038

University of Montana

10. Naylor, Jaylene R. A radiation-driven wind model for massive stars: The effects of non-isothermal and finite disk assumptions.

Degree: MS, 1999, University of Montana

URL: https://scholarworks.umt.edu/etd/8328

Subjects/Keywords: Stellar winds.; Mass loss (Astrophysics); Stars Radiation.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Naylor, J. R. (1999). A radiation-driven wind model for massive stars: The effects of non-isothermal and finite disk assumptions. (Masters Thesis). University of Montana. Retrieved from https://scholarworks.umt.edu/etd/8328

Chicago Manual of Style (16^th Edition):

Naylor, Jaylene R. “A radiation-driven wind model for massive stars: The effects of non-isothermal and finite disk assumptions.” 1999. Masters Thesis, University of Montana. Accessed March 07, 2021. https://scholarworks.umt.edu/etd/8328.

MLA Handbook (7^th Edition):

Naylor, Jaylene R. “A radiation-driven wind model for massive stars: The effects of non-isothermal and finite disk assumptions.” 1999. Web. 07 Mar 2021.

Vancouver:

Naylor JR. A radiation-driven wind model for massive stars: The effects of non-isothermal and finite disk assumptions. [Internet] [Masters thesis]. University of Montana; 1999. [cited 2021 Mar 07]. Available from: https://scholarworks.umt.edu/etd/8328.

Council of Science Editors:

Naylor JR. A radiation-driven wind model for massive stars: The effects of non-isothermal and finite disk assumptions. [Masters Thesis]. University of Montana; 1999. Available from: https://scholarworks.umt.edu/etd/8328

Rochester Institute of Technology

11. Montez, Rodolfo. X-rays from planetary nebulae: Unveiling wind collisions and binarity.

Degree: PhD, School of Physics and Astronomy (COS), 2010, Rochester Institute of Technology

URL: https://scholarworks.rit.edu/theses/36

► Planetary nebulae (PNe), the ionized, ejected envelopes of low- to intermediate-mass stars, are thought to be shaped by a nascent fast wind from the spent… (more)

▼ Planetary nebulae (PNe), the ionized, ejected envelopes of low- to intermediate-mass stars, are thought to be shaped by a nascent fast wind from the spent core (a future white dwarf) that collides with and sweeps up previously ejected material (red and asymptotic branch giant winds). This collision can generate an X-ray emitting "hot bubble" that fills the swept-up cavity. Circumstellar material in a dense torus or disk, likely due to an interacting binary in the PN nucleus, is widely believed to collimate the winds that shape non-spherical PNe. Hence, PNe offer excellent opportunities to study astrophysical shocks and binary interactions. In my thesis, I address these topics via a comprehensive analysis of new and archival (pointed and serendipitous) X-ray observations performed by Chandra and XMM-Newton X-ray satellite observatories. This analysis yields new information on the X-ray characteristics (detections and non-detections) of over 50 PNe (~40% of which were detected). Based on spatial/spectral analysis of a dozen diffuse X-ray emitting PNe, I confirm that hot bubble temperatures are generally much lower than predicted by simple shock models given measured central star fast wind velocities. Comparison of the X-ray emission and central star properties of the sample PNe with the predictions of heat conduction models indicates that some hot bubbles are regulated by heat conduction, while others appear to require alternative temperature-regulating mechanisms. From new detections of point-like hard X-ray emission from the binary star nuclei of LoTr5, DS1, and HFG1, I demonstrate that the X-ray emission most likely arises from rejuvenated coronae around the spun-up companions in these systems. These results place constraints on putative spun-up binary companions within other PNe in which point-like central sources have gone undetected by XMM and/or Chandra. I conclude with suggestions as to the most promising directions for future X-ray observations of PNe. Advisors/Committee Members: Kastner, Joel.

Subjects/Keywords: Binary stars; Planetary nebula; Shocks; Stellar evolution; Stellar winds; X-rays

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APA (6^th Edition):

Montez, R. (2010). X-rays from planetary nebulae: Unveiling wind collisions and binarity. (Doctoral Dissertation). Rochester Institute of Technology. Retrieved from https://scholarworks.rit.edu/theses/36

Chicago Manual of Style (16^th Edition):

Montez, Rodolfo. “X-rays from planetary nebulae: Unveiling wind collisions and binarity.” 2010. Doctoral Dissertation, Rochester Institute of Technology. Accessed March 07, 2021. https://scholarworks.rit.edu/theses/36.

MLA Handbook (7^th Edition):

Montez, Rodolfo. “X-rays from planetary nebulae: Unveiling wind collisions and binarity.” 2010. Web. 07 Mar 2021.

Vancouver:

Montez R. X-rays from planetary nebulae: Unveiling wind collisions and binarity. [Internet] [Doctoral dissertation]. Rochester Institute of Technology; 2010. [cited 2021 Mar 07]. Available from: https://scholarworks.rit.edu/theses/36.

Council of Science Editors:

Montez R. X-rays from planetary nebulae: Unveiling wind collisions and binarity. [Doctoral Dissertation]. Rochester Institute of Technology; 2010. Available from: https://scholarworks.rit.edu/theses/36

Universiteit Utrecht

12. Gent, Jeroen Ivar van. The Baldwin-effect in Wolf-Rayet stars.

Degree: 2000, Universiteit Utrecht

URL: http://dspace.library.uu.nl:8080/handle/1874/647

► This thesis investigates the Baldwin-effect in Wolf-Rayet (WR) stars. The Baldwin-effect is a correlation with negative slope between the equivalent width of spectral emission lines… (more)

▼ This thesis investigates the Baldwin-effect in Wolf-Rayet (WR) stars. The Baldwin-effect is a correlation with negative slope between the equivalent width of spectral emission lines and the monochromatic luminosity of the underlying continuum at the line wavelength. This effect has been known to exist in spectra of Active Galactic Nuclei and WR stars. The Baldwin effect in WR stars may function as a distance estimator, as it may provide a method to derive the stellar luminosity directly from the spectrum. Distances of WR stars are hard to derive. These stars lose matter in the form of a strong stellar wind, which hides the underlying star from view. The dense stellar wind is the reason that absolute visual magnitudes of WR stars do not correlate well with the star's temperature or intrinsic colours. Therefore, the derivation of the distance of a WR star through observational properties is not an easy task to perform. The research of this thesis confirms previous thoughts that the Baldwin effect in WR stars is mainly caused by differences in radius among stars, reflecting differences in wind density. Furthermore, it is found that the spread in the equivalent width-luminosity relations is caused by diffences in mass-loss rate and terminal wind velocity among stars and, to a lesser extend, differences in stellar temperature. This theoretical explanation of the Baldwin-effect is done by comparing simple semi-analytical expressions with the results of model stellar atmosphere calculations. For the application of the Baldwin-effect to estimate WR star distances, it is found that a reasonably accurate estimate of the mass-loss rate is required. However, the derived mass-loss rates of WR stars generally depend on an assumed distance of the star. Therefore it is tried to combine several mass-loss studies and find typical values of the mass-loss rate as function of stellar subtype. After adopting a value of the mass-loss rate for its spectral subtype, the distance of the star can be estimated through the Baldwin-effect. The performance of the Baldwin-effect as a distance estimator is tested by concentrating at WR stars with well known distances, such as those in the Large Magellanic Cloud or WR stars that are a member of an open star cluster or OB association. It is concluded that estimating WR star distances by means of this method does give a reasonable indication of the stellar distance, but often not better than existing methods.

Subjects/Keywords: Natuur- en Sterrenkunde; stars; stellar atmospheres; Wolf-Rayet stars; model atmospheres; emission lines; mass-loss; stellar winds; distances; spectra; astrophysics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Gent, J. I. v. (2000). The Baldwin-effect in Wolf-Rayet stars. (Doctoral Dissertation). Universiteit Utrecht. Retrieved from http://dspace.library.uu.nl:8080/handle/1874/647

Chicago Manual of Style (16^th Edition):

Gent, Jeroen Ivar van. “The Baldwin-effect in Wolf-Rayet stars.” 2000. Doctoral Dissertation, Universiteit Utrecht. Accessed March 07, 2021. http://dspace.library.uu.nl:8080/handle/1874/647.

MLA Handbook (7^th Edition):

Gent, Jeroen Ivar van. “The Baldwin-effect in Wolf-Rayet stars.” 2000. Web. 07 Mar 2021.

Vancouver:

Gent JIv. The Baldwin-effect in Wolf-Rayet stars. [Internet] [Doctoral dissertation]. Universiteit Utrecht; 2000. [cited 2021 Mar 07]. Available from: http://dspace.library.uu.nl:8080/handle/1874/647.

Council of Science Editors:

Gent JIv. The Baldwin-effect in Wolf-Rayet stars. [Doctoral Dissertation]. Universiteit Utrecht; 2000. Available from: http://dspace.library.uu.nl:8080/handle/1874/647

13. Gent, Jeroen Ivar van. The Baldwin-effect in Wolf-Rayet stars.

Degree: 2000, University Utrecht

URL: https://dspace.library.uu.nl/handle/1874/647 ; URN:NBN:NL:UI:10-1874-647 ; 1874/647 ; URN:NBN:NL:UI:10-1874-647 ; https://dspace.library.uu.nl/handle/1874/647

► This thesis investigates the Baldwin-effect in Wolf-Rayet (WR) stars. The Baldwin-effect is a correlation with negative slope between the equivalent width of spectral emission lines… (more)

▼ This thesis investigates the Baldwin-effect in Wolf-Rayet (WR) stars. The Baldwin-effect is a correlation with negative slope between the equivalent width of spectral emission lines and the monochromatic luminosity of the underlying continuum at the line wavelength. This effect has been known to exist in spectra of Active Galactic Nuclei and WR stars. The Baldwin effect in WR stars may function as a distance estimator, as it may provide a method to derive the stellar luminosity directly from the spectrum. Distances of WR stars are hard to derive. These stars lose matter in the form of a strong stellar wind, which hides the underlying star from view. The dense stellar wind is the reason that absolute visual magnitudes of WR stars do not correlate well with the star's temperature or intrinsic colours. Therefore, the derivation of the distance of a WR star through observational properties is not an easy task to perform. The research of this thesis confirms previous thoughts that the Baldwin effect in WR stars is mainly caused by differences in radius among stars, reflecting differences in wind density. Furthermore, it is found that the spread in the equivalent width-luminosity relations is caused by diffences in mass-loss rate and terminal wind velocity among stars and, to a lesser extend, differences in stellar temperature. This theoretical explanation of the Baldwin-effect is done by comparing simple semi-analytical expressions with the results of model stellar atmosphere calculations. For the application of the Baldwin-effect to estimate WR star distances, it is found that a reasonably accurate estimate of the mass-loss rate is required. However, the derived mass-loss rates of WR stars generally depend on an assumed distance of the star. Therefore it is tried to combine several mass-loss studies and find typical values of the mass-loss rate as function of stellar subtype. After adopting a value of the mass-loss rate for its spectral subtype, the distance of the star can be estimated through the Baldwin-effect. The performance of the Baldwin-effect as a distance estimator is tested by concentrating at WR stars with well known distances, such as those in the Large Magellanic Cloud or WR stars that are a member of an open star cluster or OB association. It is concluded that estimating WR star distances by means of this method does give a reasonable indication of the stellar distance, but often not better than existing methods.

Subjects/Keywords: stars; stellar atmospheres; Wolf-Rayet stars; model atmospheres; emission lines; mass-loss; stellar winds; distances; spectra; astrophysics

Record Details Similar Records Cite « Share

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Gent, J. I. v. (2000). The Baldwin-effect in Wolf-Rayet stars. (Doctoral Dissertation). University Utrecht. Retrieved from https://dspace.library.uu.nl/handle/1874/647 ; URN:NBN:NL:UI:10-1874-647 ; 1874/647 ; URN:NBN:NL:UI:10-1874-647 ; https://dspace.library.uu.nl/handle/1874/647

Chicago Manual of Style (16^th Edition):

Gent, Jeroen Ivar van. “The Baldwin-effect in Wolf-Rayet stars.” 2000. Doctoral Dissertation, University Utrecht. Accessed March 07, 2021. https://dspace.library.uu.nl/handle/1874/647 ; URN:NBN:NL:UI:10-1874-647 ; 1874/647 ; URN:NBN:NL:UI:10-1874-647 ; https://dspace.library.uu.nl/handle/1874/647.

MLA Handbook (7^th Edition):

Gent, Jeroen Ivar van. “The Baldwin-effect in Wolf-Rayet stars.” 2000. Web. 07 Mar 2021.

Vancouver:

Gent JIv. The Baldwin-effect in Wolf-Rayet stars. [Internet] [Doctoral dissertation]. University Utrecht; 2000. [cited 2021 Mar 07]. Available from: https://dspace.library.uu.nl/handle/1874/647 ; URN:NBN:NL:UI:10-1874-647 ; 1874/647 ; URN:NBN:NL:UI:10-1874-647 ; https://dspace.library.uu.nl/handle/1874/647.

Council of Science Editors:

Gent JIv. The Baldwin-effect in Wolf-Rayet stars. [Doctoral Dissertation]. University Utrecht; 2000. Available from: https://dspace.library.uu.nl/handle/1874/647 ; URN:NBN:NL:UI:10-1874-647 ; 1874/647 ; URN:NBN:NL:UI:10-1874-647 ; https://dspace.library.uu.nl/handle/1874/647

University of Toledo

14. Thompson, Gregory Brandon. Time-series Analysis of Line Profile Variability in Optical Spectra of ε Orionis.

Degree: PhD, Physics, 2009, University of Toledo

URL: http://rave.ohiolink.edu/etdc/view?acc_num=toledo1249511358

► The subject of this thesis is the time-series analysis of 130 échelle spectra of ε Ori obtained at Ritter Observatory on the campus of… (more)

▼ The subject of this thesis is the time-series analysis of 130 échelle spectra of ε Ori obtained at Ritter Observatory on the campus of the University of Toledo. These data were acquired over seven observing seasons between 1998 and 2006. The spectra include the Hα line, which is formed mainly in the inner wind region, and the He I λ5876 triplet, which is mostly a photospheric absorption line with weak wind features present in the wings. The equivalent widths of Hα (net) and the He I were measured and radial velocity measurements were obtained from the central absorption of the He I line. Temporal variance spectra were computed in order to quantify the variability and revealed significant wind variability in both Hα and He I. The He I TVS had a double-peaked profile consistent with radial velocity oscillations due to pulsations. Periodicity searches were carried out on the equivalent width, radial velocity and wavelength-binned spectral time series. A method developed by Bretthorst (2001) which applies Bayesian inference to the Lomb-Scargle (Lomb, 1976; Scargle, 1982) periodogram has been used in the period search on all data. The CLEAN algorithm (Roberts, Lehar, and Dreher, 1987) was also applied to the equivalent width time series. The Bayesian technique was used to construct 2D periodograms from the wavelength-binned spectra. This research has uncovered several apparently real periods. Signals with time scales on the order of the rotational period, which may be due to rotationally modulated structure, were detected in data from two seasons. Many periods with time scales of 2-8 d are present in the data. A photospheric origin is suspected for periods present in He I and radial velocity data but a wind origin cannot be ruled out. The periods detected in the Hα data are likely due to wind variability. A period of 4.4 d, was detected in nearly every season. This period was found in both Hα and He I and may indicate a persistent or recurring phenomenon. A 2.2 d period was detected in the radial velocity data that may be the overtone of the 4.4 d period. The periods have times scales consistent with non-radial pulsations. Pulsations may be inducing harmonic modulation of the wind. Advisors/Committee Members: Morrison, Nancy (Advisor).

Subjects/Keywords: Astronomy; Astrophysics; line profile variability; time-series analysis; massive stars; early-type stars; hot supergiants; stellar winds; stellar pulsations

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Thompson, G. B. (2009). Time-series Analysis of Line Profile Variability in Optical Spectra of ε Orionis. (Doctoral Dissertation). University of Toledo. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=toledo1249511358

Chicago Manual of Style (16^th Edition):

Thompson, Gregory Brandon. “Time-series Analysis of Line Profile Variability in Optical Spectra of ε Orionis.” 2009. Doctoral Dissertation, University of Toledo. Accessed March 07, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1249511358.

MLA Handbook (7^th Edition):

Thompson, Gregory Brandon. “Time-series Analysis of Line Profile Variability in Optical Spectra of ε Orionis.” 2009. Web. 07 Mar 2021.

Vancouver:

Thompson GB. Time-series Analysis of Line Profile Variability in Optical Spectra of ε Orionis. [Internet] [Doctoral dissertation]. University of Toledo; 2009. [cited 2021 Mar 07]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=toledo1249511358.

Council of Science Editors:

Thompson GB. Time-series Analysis of Line Profile Variability in Optical Spectra of ε Orionis. [Doctoral Dissertation]. University of Toledo; 2009. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=toledo1249511358

North-West University

15. Van den Heever, Stefanus Petrus. Numerical modelling of stellar winds for supernova progenitors / Stefanus Petrus van den Heever.

Degree: 2011, North-West University

URL: http://hdl.handle.net/10394/9719

► A two-dimensional hydrodynamic numerical model is extended and applied to simulate the interaction between stellar winds and the interstellar medium (ISM). In particular, the stellar… (more)

▼ A two-dimensional hydrodynamic numerical model is extended and applied to simulate the interaction between stellar winds and the interstellar medium (ISM). In particular, the stellar wind evolution of O- and B-type stars is calculated. First, the evolution of a stellar wind into the ambient interstellar medium and also a more dense molecular cloud are considered for the case of no relative motion between the star and the interstellar medium. This interaction results in a cavity being blown into the ISM. Of importance in this work is the boundary radius (astropause) of the stellar wind and also the location where the outflow speed decreases from supersonic to subsonic speeds, called the termination shock. Different parameters like ISM density, outflow speed and mass-loss rate were varied to study the effect these have on the computed astropause (AP) and termination shock (TS) radii. The evolution of these structures is presented up to a simulation time of 1 My. However, stars are not stationary relative to the ISM, and the evolution of stellar winds into the interstellar medium including relative motion is also considered. It is shown that the positions of the TS and AP are dependent on the mass-loss rate and stellar wind outflow speed of the star and the interstellar medium density and relative speed. When these massive stars reach the end of their life, they end their life in a supernova explosion. The explosion results in a blast wave moving outward, called the forward shock (FS) and a reverse shock (RS) also forms which moves inward. Previous work done by Ferreira and de Jager (2008) to simulate supernova remnant (SNR) evolution, was only done for the case of evolution into the undisturbed ISM (no cavity). In this work, the evolution of SNR is simulated taking also into account the pre-existing cavity blown out by the stellar winds of these massive stars. The results of this study showed that the evolution of the SNR is definitely influenced by the presence of a stellar wind cavity even if the cavity is only a few pc in extent.

Subjects/Keywords: Stellar winds; interstellar medium; O- and B-type stars; termination shock; astropause; supernova remnant; molecular cloud; stellêre winde; interstellêre medium; O en B-tipe sterre; terminasieskok; astropouse; supernova-res; molekulêre wolk

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APA (6^th Edition):

Van den Heever, S. P. (2011). Numerical modelling of stellar winds for supernova progenitors / Stefanus Petrus van den Heever. (Thesis). North-West University. Retrieved from http://hdl.handle.net/10394/9719

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Van den Heever, Stefanus Petrus. “Numerical modelling of stellar winds for supernova progenitors / Stefanus Petrus van den Heever. ” 2011. Thesis, North-West University. Accessed March 07, 2021. http://hdl.handle.net/10394/9719.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Van den Heever, Stefanus Petrus. “Numerical modelling of stellar winds for supernova progenitors / Stefanus Petrus van den Heever. ” 2011. Web. 07 Mar 2021.

Vancouver:

Van den Heever SP. Numerical modelling of stellar winds for supernova progenitors / Stefanus Petrus van den Heever. [Internet] [Thesis]. North-West University; 2011. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/10394/9719.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Van den Heever SP. Numerical modelling of stellar winds for supernova progenitors / Stefanus Petrus van den Heever. [Thesis]. North-West University; 2011. Available from: http://hdl.handle.net/10394/9719

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Université de Montréal

16. Ramiaramanantsoa, Tahina. Sur les origines photosphériques des structures dans les vents des étoiles chaudes et lumineuses.

Degree: 2018, Université de Montréal

URL: http://hdl.handle.net/1866/21152

Subjects/Keywords: Étoiles massives; Taches stellaires; Vents stellaires; Photométrie; Spectroscopie; Astérosismologie; Xi Persei; Zeta Puppis; V973 Scorpii; Massive stars; Starspots; Stellar winds; Photometry; Spectroscopy; Asteroseismology; Physics - Astronomy and Astrophysics / Physique - Astronomie et astrophysique (UMI : 0606)

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Ramiaramanantsoa, T. (2018). Sur les origines photosphériques des structures dans les vents des étoiles chaudes et lumineuses. (Thesis). Université de Montréal. Retrieved from http://hdl.handle.net/1866/21152

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Ramiaramanantsoa, Tahina. “Sur les origines photosphériques des structures dans les vents des étoiles chaudes et lumineuses.” 2018. Thesis, Université de Montréal. Accessed March 07, 2021. http://hdl.handle.net/1866/21152.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Ramiaramanantsoa, Tahina. “Sur les origines photosphériques des structures dans les vents des étoiles chaudes et lumineuses.” 2018. Web. 07 Mar 2021.

Vancouver:

Ramiaramanantsoa T. Sur les origines photosphériques des structures dans les vents des étoiles chaudes et lumineuses. [Internet] [Thesis]. Université de Montréal; 2018. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/1866/21152.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Ramiaramanantsoa T. Sur les origines photosphériques des structures dans les vents des étoiles chaudes et lumineuses. [Thesis]. Université de Montréal; 2018. Available from: http://hdl.handle.net/1866/21152

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Université de Montréal

17. Carlos-Leblanc, Danny. Simulations Monte Carlo de régions d'interaction en corotation dans le vent d'étoiles chaudes.

Degree: 2019, Université de Montréal

URL: http://hdl.handle.net/1866/22717

Subjects/Keywords: Vents stellaires; étoiles massives; polarisation; structures à grande échelle; transfert radiatif; simulation Monte Carlo; méthode: numérique; Stellar winds; Massive stars; Methods: numerical; Polarization; Large-scale structures; Radiative transfer; Monte Carlo simulations; Physics - Astronomy and Astrophysics / Physique - Astronomie et astrophysique (UMI : 0606)

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APA (6^th Edition):

Carlos-Leblanc, D. (2019). Simulations Monte Carlo de régions d'interaction en corotation dans le vent d'étoiles chaudes. (Thesis). Université de Montréal. Retrieved from http://hdl.handle.net/1866/22717

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Carlos-Leblanc, Danny. “Simulations Monte Carlo de régions d'interaction en corotation dans le vent d'étoiles chaudes.” 2019. Thesis, Université de Montréal. Accessed March 07, 2021. http://hdl.handle.net/1866/22717.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Carlos-Leblanc, Danny. “Simulations Monte Carlo de régions d'interaction en corotation dans le vent d'étoiles chaudes.” 2019. Web. 07 Mar 2021.

Vancouver:

Carlos-Leblanc D. Simulations Monte Carlo de régions d'interaction en corotation dans le vent d'étoiles chaudes. [Internet] [Thesis]. Université de Montréal; 2019. [cited 2021 Mar 07]. Available from: http://hdl.handle.net/1866/22717.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Carlos-Leblanc D. Simulations Monte Carlo de régions d'interaction en corotation dans le vent d'étoiles chaudes. [Thesis]. Université de Montréal; 2019. Available from: http://hdl.handle.net/1866/22717

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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