subject:(Accretion Disk)

Addis Ababa University

1. HAFTAMU, G/MARIAM. THE CONTRIBUTION OF RADIATION PRESSURE TO THE STABILITY OF A STANDARD THIN KEPLERIAN ACCRETION DISK AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC FIELD DIPOLE .

Degree: 2012, Addis Ababa University

URL: http://etd.aau.edu.et/dspace/handle/123456789/1280

► In this thesis, we have studied the dynamic properties of an accretion disk formed from the in ow of plasma from a blotted out companion… (more)

Subjects/Keywords: AXISYMMETRIC; KEPLERIAN ACCRETION DISK

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

APA (6^th Edition):

HAFTAMU, G. (2012). THE CONTRIBUTION OF RADIATION PRESSURE TO THE STABILITY OF A STANDARD THIN KEPLERIAN ACCRETION DISK AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC FIELD DIPOLE . (Thesis). Addis Ababa University. Retrieved from http://etd.aau.edu.et/dspace/handle/123456789/1280

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):

HAFTAMU, G/MARIAM. “THE CONTRIBUTION OF RADIATION PRESSURE TO THE STABILITY OF A STANDARD THIN KEPLERIAN ACCRETION DISK AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC FIELD DIPOLE .” 2012. Thesis, Addis Ababa University. Accessed January 17, 2021. http://etd.aau.edu.et/dspace/handle/123456789/1280.

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

MLA Handbook (7^th Edition):

HAFTAMU, G/MARIAM. “THE CONTRIBUTION OF RADIATION PRESSURE TO THE STABILITY OF A STANDARD THIN KEPLERIAN ACCRETION DISK AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC FIELD DIPOLE .” 2012. Web. 17 Jan 2021.

Vancouver:

HAFTAMU G. THE CONTRIBUTION OF RADIATION PRESSURE TO THE STABILITY OF A STANDARD THIN KEPLERIAN ACCRETION DISK AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC FIELD DIPOLE . [Internet] [Thesis]. Addis Ababa University; 2012. [cited 2021 Jan 17]. Available from: http://etd.aau.edu.et/dspace/handle/123456789/1280.

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

Council of Science Editors:

HAFTAMU G. THE CONTRIBUTION OF RADIATION PRESSURE TO THE STABILITY OF A STANDARD THIN KEPLERIAN ACCRETION DISK AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC FIELD DIPOLE . [Thesis]. Addis Ababa University; 2012. Available from: http://etd.aau.edu.et/dspace/handle/123456789/1280

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

Indian Institute of Science

2. Rajesh, S R. Stability of Accretion Flows And Radiative-Hydrodynamics Around Rotating Black Holes.

Degree: PhD, Faculty of Science, 2013, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/2076

► In the case of cold accretion disk, coupling between charge neutral gas and magnetic field is too weak such that the magneto-rotational instability will be… (more)

▼ In the case of cold accretion disk, coupling between charge neutral gas and magnetic field is too weak such that the magneto-rotational instability will be less effective or even stop working. In such a situation it is of prime interest to investigate the pure hydrodynamic turbulence and transport phenomenon. As the Reynolds number increases, the relative importance of the non-linear term in the hydrodynamic equation increases and in the case of accretion disk where molecular viscosity is too small the Reynolds number is large enough for the non-linear term to bring new effects. We investigate a scenario, the ‘weakly non-linear’ evolution of amplitude of linear mode when the flow is bounded by two parallel walls. The unperturbed flow is similar to plane Couette flow but with Coriolis force included in the hydrodynamic equation. Although there is no exponentially growing eigenmode, due to self-interaction the least stable eigenmode will grow in an intermediate phase. Later on this will lead to higher order non-linearity and plausible turbulence. Although the non-linear term in the hydrodynamic equation is energy conserving, within the weakly non-linear analysis it is possible to deﬁne a lower bound of the energy needed for flow to transform to turbulent phase. Such an unstable phase is possible only if the Reynolds number ≥ 103−4. In Chapter-2 we set up equation of amplitude for the hydrodynamic perturbation and study the effect of weak non-linear evolution of linear mode for general angular momentum distribution, where Keplerian disk is obtained as a special case. As we know that to explain observed hard X-rays the choice of Keplerian angular momentum profile is not adequate, we consider the sub-Keplerian regime of the disk. In Chapter-3 we assume that the cooling mechanism is dominated by bremsstrahlung process (without any strict knowledge of the magnetic field structure).We show that in a range of Shakura-Sunyaev viscosity 0.2 ≥ α ≥ 0.0005, flow behavior varies widely, particularly by means of the size of disk, efficiency of cooling and corresponding temperatures of ions and electrons. We also show that the disk around a rotating black hole is hotter compared to that around a Schwarzschild black hole, rendering a larger difference between ion and electron temperatures in the former case. We finally reproduce the observed luminosities(L) of two extreme cases—the under-fed AGNs and quasars and ultra-luminous X-ray sources at different combinations of mass accretion rate, ratio of specific heats, Shakura-Sunyaev viscosity parameter and Kerr parameter. In Chapter-4 we investigate the viscous two temperature accretion disk flows around rotating blackholes. We describe the global solution of accretion flows, unlike that in Chapter-3, with a sub-Keplerian angular momentum profile, by solving the underlying conservation equations including explicit cooling processes self-consistently. Bremsstrahlung, synchrotron and inverse comptonization of soft photons are considered as possible cooling mechanisms. We focus on the set… Advisors/Committee Members: Mukhopadhyay, Banibrata (advisor).

Subjects/Keywords: Black Holes; Radiative-hydrodynamics; Accretion Flows; Accretion (Astrophysics); Accretion Disc; Accretion Disk - Hydrodynamic Instability; Blackholes; Astrophysics

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

APA (6^th Edition):

Rajesh, S. R. (2013). Stability of Accretion Flows And Radiative-Hydrodynamics Around Rotating Black Holes. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/2076

Chicago Manual of Style (16^th Edition):

Rajesh, S R. “Stability of Accretion Flows And Radiative-Hydrodynamics Around Rotating Black Holes.” 2013. Doctoral Dissertation, Indian Institute of Science. Accessed January 17, 2021. http://etd.iisc.ac.in/handle/2005/2076.

MLA Handbook (7^th Edition):

Rajesh, S R. “Stability of Accretion Flows And Radiative-Hydrodynamics Around Rotating Black Holes.” 2013. Web. 17 Jan 2021.

Vancouver:

Rajesh SR. Stability of Accretion Flows And Radiative-Hydrodynamics Around Rotating Black Holes. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2013. [cited 2021 Jan 17]. Available from: http://etd.iisc.ac.in/handle/2005/2076.

Council of Science Editors:

Rajesh SR. Stability of Accretion Flows And Radiative-Hydrodynamics Around Rotating Black Holes. [Doctoral Dissertation]. Indian Institute of Science; 2013. Available from: http://etd.iisc.ac.in/handle/2005/2076

Addis Ababa University

3. GEREZIHER, HAGOS. THE CONTRIBUTION OF COULOMBIC PRESSURE TO THE STABILITY OF THIN KEPLERIAN ACCRETION DISCS AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC DIPOLE .

Degree: 2012, Addis Ababa University

URL: http://etd.aau.edu.et/dspace/handle/123456789/1275

► We determine the stability of an axisymmetric geometrically thin and optically thick accretion disc around a magnetized neutron star in the region where gas pressure… (more)

Subjects/Keywords: accretion disc; magnetized neutron star

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

APA (6^th Edition):

GEREZIHER, H. (2012). THE CONTRIBUTION OF COULOMBIC PRESSURE TO THE STABILITY OF THIN KEPLERIAN ACCRETION DISCS AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC DIPOLE . (Thesis). Addis Ababa University. Retrieved from http://etd.aau.edu.et/dspace/handle/123456789/1275

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):

GEREZIHER, HAGOS. “THE CONTRIBUTION OF COULOMBIC PRESSURE TO THE STABILITY OF THIN KEPLERIAN ACCRETION DISCS AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC DIPOLE .” 2012. Thesis, Addis Ababa University. Accessed January 17, 2021. http://etd.aau.edu.et/dspace/handle/123456789/1275.

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

MLA Handbook (7^th Edition):

GEREZIHER, HAGOS. “THE CONTRIBUTION OF COULOMBIC PRESSURE TO THE STABILITY OF THIN KEPLERIAN ACCRETION DISCS AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC DIPOLE .” 2012. Web. 17 Jan 2021.

Vancouver:

GEREZIHER H. THE CONTRIBUTION OF COULOMBIC PRESSURE TO THE STABILITY OF THIN KEPLERIAN ACCRETION DISCS AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC DIPOLE . [Internet] [Thesis]. Addis Ababa University; 2012. [cited 2021 Jan 17]. Available from: http://etd.aau.edu.et/dspace/handle/123456789/1275.

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

Council of Science Editors:

GEREZIHER H. THE CONTRIBUTION OF COULOMBIC PRESSURE TO THE STABILITY OF THIN KEPLERIAN ACCRETION DISCS AROUND A NEUTRON STAR WITH AXISYMMETRIC MAGNETIC DIPOLE . [Thesis]. Addis Ababa University; 2012. Available from: http://etd.aau.edu.et/dspace/handle/123456789/1275

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

Penn State University

4. Flohic, Helene Marie. INTERPRETING DOUBLE-PEAKED EMISSION LINE PROFILE VARIABILITY IN AGNS USING MODELS FOR ACCRETION DISK STRUCTURES .

Degree: 2008, Penn State University

URL: https://submit-etda.libraries.psu.edu/catalog/9233

► A subset of Active Galactic Nuclei (AGNs) have broad, double-peaked Balmer emission lines, regarded as the best kinematic evidence for the production of broad lines… (more)

Subjects/Keywords: AGNs; accretion disk

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

APA (6^th Edition):

Flohic, H. M. (2008). INTERPRETING DOUBLE-PEAKED EMISSION LINE PROFILE VARIABILITY IN AGNS USING MODELS FOR ACCRETION DISK STRUCTURES . (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/9233

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):

Flohic, Helene Marie. “INTERPRETING DOUBLE-PEAKED EMISSION LINE PROFILE VARIABILITY IN AGNS USING MODELS FOR ACCRETION DISK STRUCTURES .” 2008. Thesis, Penn State University. Accessed January 17, 2021. https://submit-etda.libraries.psu.edu/catalog/9233.

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

MLA Handbook (7^th Edition):

Flohic, Helene Marie. “INTERPRETING DOUBLE-PEAKED EMISSION LINE PROFILE VARIABILITY IN AGNS USING MODELS FOR ACCRETION DISK STRUCTURES .” 2008. Web. 17 Jan 2021.

Vancouver:

Flohic HM. INTERPRETING DOUBLE-PEAKED EMISSION LINE PROFILE VARIABILITY IN AGNS USING MODELS FOR ACCRETION DISK STRUCTURES . [Internet] [Thesis]. Penn State University; 2008. [cited 2021 Jan 17]. Available from: https://submit-etda.libraries.psu.edu/catalog/9233.

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

Council of Science Editors:

Flohic HM. INTERPRETING DOUBLE-PEAKED EMISSION LINE PROFILE VARIABILITY IN AGNS USING MODELS FOR ACCRETION DISK STRUCTURES . [Thesis]. Penn State University; 2008. Available from: https://submit-etda.libraries.psu.edu/catalog/9233

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

University of Guelph

5. Russell, John L. Development of a Self-Consistent Gas Accretion Model for Simulating Gas Giant Formation in Protoplanetary Disks.

Degree: MS, Department of Physics, 2011, University of Guelph

URL: https://atrium.lib.uoguelph.ca/xmlui/handle/10214/3212

► The number of extrasolar planet discoveries has increased dramatically over the last 15 years. Nearly 700 exoplanets have currently been observed through a variety of… (more)

Subjects/Keywords: astrophysics; accretion disk; protoplanetary disk; planet formation; gas giant; exoplanet; accretion; planets; FARGO

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

APA (6^th Edition):

Russell, J. L. (2011). Development of a Self-Consistent Gas Accretion Model for Simulating Gas Giant Formation in Protoplanetary Disks. (Masters Thesis). University of Guelph. Retrieved from https://atrium.lib.uoguelph.ca/xmlui/handle/10214/3212

Chicago Manual of Style (16^th Edition):

Russell, John L. “Development of a Self-Consistent Gas Accretion Model for Simulating Gas Giant Formation in Protoplanetary Disks.” 2011. Masters Thesis, University of Guelph. Accessed January 17, 2021. https://atrium.lib.uoguelph.ca/xmlui/handle/10214/3212.

MLA Handbook (7^th Edition):

Russell, John L. “Development of a Self-Consistent Gas Accretion Model for Simulating Gas Giant Formation in Protoplanetary Disks.” 2011. Web. 17 Jan 2021.

Vancouver:

Russell JL. Development of a Self-Consistent Gas Accretion Model for Simulating Gas Giant Formation in Protoplanetary Disks. [Internet] [Masters thesis]. University of Guelph; 2011. [cited 2021 Jan 17]. Available from: https://atrium.lib.uoguelph.ca/xmlui/handle/10214/3212.

Council of Science Editors:

Russell JL. Development of a Self-Consistent Gas Accretion Model for Simulating Gas Giant Formation in Protoplanetary Disks. [Masters Thesis]. University of Guelph; 2011. Available from: https://atrium.lib.uoguelph.ca/xmlui/handle/10214/3212

University of Cambridge

6. Kosec, Peter. Studying accretion disc winds with X-ray spectroscopy.

Degree: PhD, 2020, University of Cambridge

URL: https://doi.org/10.17863/CAM.57704 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.814569

► In this thesis I present the results of my PhD research into the physics of accretion (infall) and ejection (outflow) of matter in compact objects.… (more)

▼ In this thesis I present the results of my PhD research into the physics of accretion (infall) and ejection (outflow) of matter in compact objects. Accretion disc winds are formed of hot and ionised material launched by magnetic forces, radiation pressure or thermally from the discs of accretors. They have been discovered in most types of accreting systems including supermassive black holes, classical X-ray binaries and Ultraluminous X-ray sources. Outflows form a ubiquitous and important part of the accretion flow, carrying away a considerable fraction of the originally infalling mass. With velocities as high as 30 per cent of the speed of light, their kinetic energy budget can also be significant and have a strong impact on the accretor surroundings. Ultra-fast outflows from supermassive black holes could contribute to or even drive active galactic nucleus feedback in galaxies. Accretion disc winds can be observed through Doppler-shifted spectral lines in the X-ray part of the electromagnetic spectrum, the wind physical properties can thus be studied with X-ray spectroscopy. In this work, I present the detection of disc winds and I study their physics in a number of accreting systems. I particularly make use of the high-spectral resolution Reflection Grating Spectrometer onboard the XMM-Newton observatory. For efficient data analysis I develop and use systematic automated routines for search of wind signatures in X-ray spectra. The first two chapters of this thesis introduce the theory of accretion and describe different accreting systems, as well as the X-ray observatories and data analysis methods used in this study. The third chapter contains a systematic search for disc winds in a sample of Ultraluminous X-ray sources, powered by super-Eddington accretion onto stellar-mass black holes and neutron stars. In the fourth chapter I achieve the first discovery of an ultra-fast wind in a neutron star Ultraluminous X-ray source. In the following two chapters I present the detection of ultra-fast outflows from two accreting supermassive black holes PG 1448+273 and 1H 0707-495. The outflow energetics show that these winds are more than capable to drive feedback in the accretor host galaxies. Furthermore, both show evidence for a multi-phase wind structure, PG 1448+273 also exhibiting variability in time. In the seventh chapter, I present the discovery of a disc wind in the unique X-ray binary Hercules X-1 known for a precessing, warped accretion disc. I leverage the warped disc precession to sample the vertical distribution of the disc wind, constraining its launching angle as well as the total mass outflow rate, two crucial quantities which are difficult to measure in other accreting systems. The final chapter contains the conclusions of the thesis as well as potential future research avenues in this field and the promising upcoming X-ray observatories.

Subjects/Keywords: X-ray Astronomy; Accretion; Neutron Stars; Black Holes; Accretion Disc Winds

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

APA (6^th Edition):

Kosec, P. (2020). Studying accretion disc winds with X-ray spectroscopy. (Doctoral Dissertation). University of Cambridge. Retrieved from https://doi.org/10.17863/CAM.57704 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.814569

Chicago Manual of Style (16^th Edition):

Kosec, Peter. “Studying accretion disc winds with X-ray spectroscopy.” 2020. Doctoral Dissertation, University of Cambridge. Accessed January 17, 2021. https://doi.org/10.17863/CAM.57704 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.814569.

MLA Handbook (7^th Edition):

Kosec, Peter. “Studying accretion disc winds with X-ray spectroscopy.” 2020. Web. 17 Jan 2021.

Vancouver:

Kosec P. Studying accretion disc winds with X-ray spectroscopy. [Internet] [Doctoral dissertation]. University of Cambridge; 2020. [cited 2021 Jan 17]. Available from: https://doi.org/10.17863/CAM.57704 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.814569.

Council of Science Editors:

Kosec P. Studying accretion disc winds with X-ray spectroscopy. [Doctoral Dissertation]. University of Cambridge; 2020. Available from: https://doi.org/10.17863/CAM.57704 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.814569

University of Cambridge

7. Kosec, Peter. Studying Accretion Disc Winds with X-ray Spectroscopy.

Degree: PhD, 2020, University of Cambridge

URL: https://www.repository.cam.ac.uk/handle/1810/310607

► In this thesis I present the results of my PhD research into the physics of accretion (infall) and ejection (outflow) of matter in compact objects.… (more)

▼ In this thesis I present the results of my PhD research into the physics of accretion (infall) and ejection (outflow) of matter in compact objects. Accretion disc winds are formed of hot and ionised material launched by magnetic forces, radiation pressure or thermally from the discs of accretors. They have been discovered in most types of accreting systems including supermassive black holes, classical X-ray binaries and Ultraluminous X-ray sources. Outflows form a ubiquitous and important part of the accretion flow, carrying away a considerable fraction of the originally infalling mass. With velocities as high as 30 per cent of the speed of light, their kinetic energy budget can also be significant and have a strong impact on the accretor surroundings. Ultra-fast outflows from supermassive black holes could contribute to or even drive active galactic nucleus feedback in galaxies. Accretion disc winds can be observed through Doppler-shifted spectral lines in the X-ray part of the electromagnetic spectrum, the wind physical properties can thus be studied with X-ray spectroscopy. In this work, I present the detection of disc winds and I study their physics in a number of accreting systems. I particularly make use of the high-spectral resolution Reflection Grating Spectrometer onboard the XMM-Newton observatory. For efficient data analysis I develop and use systematic automated routines for search of wind signatures in X-ray spectra. The first two chapters of this thesis introduce the theory of accretion and describe different accreting systems, as well as the X-ray observatories and data analysis methods used in this study. The third chapter contains a systematic search for disc winds in a sample of Ultraluminous X-ray sources, powered by super-Eddington accretion onto stellar-mass black holes and neutron stars. In the fourth chapter I achieve the first discovery of an ultra-fast wind in a neutron star Ultraluminous X-ray source. In the following two chapters I present the detection of ultra-fast outflows from two accreting supermassive black holes PG 1448+273 and 1H 0707-495. The outflow energetics show that these winds are more than capable to drive feedback in the accretor host galaxies. Furthermore, both show evidence for a multi-phase wind structure, PG 1448+273 also exhibiting variability in time. In the seventh chapter, I present the discovery of a disc wind in the unique X-ray binary Hercules X-1 known for a precessing, warped accretion disc. I leverage the warped disc precession to sample the vertical distribution of the disc wind, constraining its launching angle as well as the total mass outflow rate, two crucial quantities which are difficult to measure in other accreting systems. The final chapter contains the conclusions of the thesis as well as potential future research avenues in this field and the promising upcoming X-ray observatories.

Subjects/Keywords: X-ray Astronomy; Accretion; Neutron Stars; Black Holes; Accretion Disc Winds

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):

Kosec, P. (2020). Studying Accretion Disc Winds with X-ray Spectroscopy. (Doctoral Dissertation). University of Cambridge. Retrieved from https://www.repository.cam.ac.uk/handle/1810/310607

Chicago Manual of Style (16^th Edition):

Kosec, Peter. “Studying Accretion Disc Winds with X-ray Spectroscopy.” 2020. Doctoral Dissertation, University of Cambridge. Accessed January 17, 2021. https://www.repository.cam.ac.uk/handle/1810/310607.

MLA Handbook (7^th Edition):

Kosec, Peter. “Studying Accretion Disc Winds with X-ray Spectroscopy.” 2020. Web. 17 Jan 2021.

Vancouver:

Kosec P. Studying Accretion Disc Winds with X-ray Spectroscopy. [Internet] [Doctoral dissertation]. University of Cambridge; 2020. [cited 2021 Jan 17]. Available from: https://www.repository.cam.ac.uk/handle/1810/310607.

Council of Science Editors:

Kosec P. Studying Accretion Disc Winds with X-ray Spectroscopy. [Doctoral Dissertation]. University of Cambridge; 2020. Available from: https://www.repository.cam.ac.uk/handle/1810/310607

8. Kadowaki, Luis Henrique Sinki. Reconexão magnética em discos de acreção e seus efeitos sobre a formação e aceleração de jatos: um estudo teórico-numérico.

Degree: Mestrado, Astronomia, 2011, University of São Paulo

URL: http://www.teses.usp.br/teses/disponiveis/14/14131/tde-15012012-121521/ ;

► Jatos e discos de acreção associados a objetos galácticos e extragalácticos tais como, microquasares (i.e., buracos negros de massa estelar presentes em alguns sistemas binários… (more)

▼ Jatos e discos de acreção associados a objetos galácticos e extragalácticos tais como, microquasares (i.e., buracos negros de massa estelar presentes em alguns sistemas binários estelares), núcleos ativos de galáxias (NAGs) e objetos estelares jovens (OEJs), frequentemente exibem eventos de ejeção de matéria quase periódicos que podem fornecer importantes informações sobre os processos físicos que ocorrem nas suas regiões mais internas. Entre essas classes de objetos, os microquasares com emissão transiente em raios-X vêm sendo identificados em nossa Galáxia desde a última década, e tal como os NAGs e quasares distantes, alguns desses sistemas também produzem jatos colimados com velocidades aparentemente superluminais, não deixando dúvidas de que se tratam de um gás ejetado com velocidades relativísticas. Um exemplo amplamente observado em comprimentos de onda do rádio aos raios-X é o microquasar GRS 1915+105 (e.g., Dhawan et al.,2000), que foi o primeiro objeto galáctico a exibir evidências de um jato com movimento aparentemente superluminal (Mirabel e Rodríguez, 1998, 1994). Um modelo para explicar a origem dessas ejeções superluminais, bem como a emissão rádio sincrotrônica em flares não muito diferentes dos que ocorrem na coroa solar, foi desenvolvido por de Gouveia Dal Pino e Lazarian (2005), onde é invocado um processo de reconexão magnética violenta entre as linhas de campo magnético que se erguem do disco de acreção e as linhas da magnetosfera da fonte central. Em episódios de acreção onde a razão entre a pressão efetiva do disco e a pressão magnética diminui para valores menores ou da ordem de 1 e as taxas de acreção se aproximam da taxa crítica de Eddington, a reconexão pode tornar-se violenta e libera grandes quantidades de energia magnética em pouco tempo. Parte dessa energia aquece o gás, tanto da coroa quanto do disco, e parte acelera as partículas a velocidades relativísticas por um processo de Fermi de primeira ordem, pela primeira vez estudado em zonas de reconexão magnética por esses autores, produzindo um espectro sincrotrônico de lei de potência com índice espectral comparável às observações. Neste trabalho realizamos um estudo complementar, iniciado por Piovezan (2009), no qual generalizamos o modelo acima descrito para o caso dos NAGs. Nesse estudo, constatamos que a atividade de reconexão magnética na região coronal, na base de lançamento do jato, pode explicar a origem das ejeções relativísticas, dos microquasares aos NAGs de baixa luminosidade (tais como galáxias Seyfert e LINERS). A potência liberada em eventos de reconexão magnética em função das massas dos buracos negros dessas fontes, de 5 massas solares a 10¹⁰ massas solares, obedece a uma correlação que se mantém por todo esse intervalo, abrangendo 10⁹ ordens de magnitude. Essa correlação implica em uma dependência quase linear (em um diagrama log-log), aproximadamente independente das características físicas locais dos discos de acreção dessas fontes. Além do mais, ela é compatível com o chamado plano fundamental, obtido… Advisors/Committee Members: Pino, Elisabete Maria de Gouveia Dal.

Subjects/Keywords: Accretion disk; Campos Magnéticos; Discos de acreção; Magnetic fields; Magnetohidrodinâmica; Magnetohydrodynamics

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

APA (6^th Edition):

Kadowaki, L. H. S. (2011). Reconexão magnética em discos de acreção e seus efeitos sobre a formação e aceleração de jatos: um estudo teórico-numérico. (Masters Thesis). University of São Paulo. Retrieved from http://www.teses.usp.br/teses/disponiveis/14/14131/tde-15012012-121521/ ;

Chicago Manual of Style (16^th Edition):

Kadowaki, Luis Henrique Sinki. “Reconexão magnética em discos de acreção e seus efeitos sobre a formação e aceleração de jatos: um estudo teórico-numérico.” 2011. Masters Thesis, University of São Paulo. Accessed January 17, 2021. http://www.teses.usp.br/teses/disponiveis/14/14131/tde-15012012-121521/ ;.

MLA Handbook (7^th Edition):

Kadowaki, Luis Henrique Sinki. “Reconexão magnética em discos de acreção e seus efeitos sobre a formação e aceleração de jatos: um estudo teórico-numérico.” 2011. Web. 17 Jan 2021.

Vancouver:

Kadowaki LHS. Reconexão magnética em discos de acreção e seus efeitos sobre a formação e aceleração de jatos: um estudo teórico-numérico. [Internet] [Masters thesis]. University of São Paulo; 2011. [cited 2021 Jan 17]. Available from: http://www.teses.usp.br/teses/disponiveis/14/14131/tde-15012012-121521/ ;.

Council of Science Editors:

Kadowaki LHS. Reconexão magnética em discos de acreção e seus efeitos sobre a formação e aceleração de jatos: um estudo teórico-numérico. [Masters Thesis]. University of São Paulo; 2011. Available from: http://www.teses.usp.br/teses/disponiveis/14/14131/tde-15012012-121521/ ;

McMaster University

9. Jackel, Benjamin. Magnetic Dynamos: How Do They Even Work?.

Degree: PhD, 2015, McMaster University

URL: http://hdl.handle.net/11375/18299

►

The origin of cosmic magnetic fields is a important area of astrophysics. The process by which they are created falls under the heading of dynamo… (more)

▼

The origin of cosmic magnetic fields is a important area of astrophysics. The process by which they are created falls under the heading of dynamo theory, and is the topic of this thesis. Our focus for the location of where these magnetic fields operate is one the most ubiquitous objects in the universe, the accretion disk. By studying the accretion disk and the dynamo process that occurs there we wish to better understand both the accretion process and the dynamo process in stars and galaxies as well. We analyse the output from a stratified zero net flux shearing box simulation performed using the ATHENA MHD code in collaboration with Shane Davis. The simulation has turbulence which is naturally forced by the presence of a linear instability called the magnetorotational instability (MRI). We utilise Fourier filtering and the tools of mean field dynamo theory to establish a connection between the calculated EMF and the model predictions of the dynamically quenched alpha model. We find a positive correlation for both components parallel to the large scale magnetic field and the azimuthal components. We have explored many aspects of the theory including additional contributions from magnetic buoyancy and an effect arising from the large scale shear and the current density. We also directly measure the turbulent correlation time for the velocity and magnetic fields both large scale and small. We can also observe the effects of the dynamo cycle, with the azimuthal component of the large scale magnetic field flipping sign in this analysis. We find a positive correlation between the divergence of the eddy scale magnetic helicity flux and the component of the electromotive force parallel to the large scale magnetic field. This correlation directly links the transfer of magnetic helicity to the dynamo process in a system with naturally driven turbulence. This highlights the importance of magnetic helicity and its conservation even in a system with triply periodic boundary conditions.

Thesis

Doctor of Philosophy (PhD)

Advisors/Committee Members: Vishniac, Ethan, Physics and Astronomy.

Subjects/Keywords: Accretion Disk; Magnetic Dynamo; magnetohydrodynamics; Mean Field Theory

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APA (6^th Edition):

Jackel, B. (2015). Magnetic Dynamos: How Do They Even Work?. (Doctoral Dissertation). McMaster University. Retrieved from http://hdl.handle.net/11375/18299

Chicago Manual of Style (16^th Edition):

Jackel, Benjamin. “Magnetic Dynamos: How Do They Even Work?.” 2015. Doctoral Dissertation, McMaster University. Accessed January 17, 2021. http://hdl.handle.net/11375/18299.

MLA Handbook (7^th Edition):

Jackel, Benjamin. “Magnetic Dynamos: How Do They Even Work?.” 2015. Web. 17 Jan 2021.

Vancouver:

Jackel B. Magnetic Dynamos: How Do They Even Work?. [Internet] [Doctoral dissertation]. McMaster University; 2015. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11375/18299.

Council of Science Editors:

Jackel B. Magnetic Dynamos: How Do They Even Work?. [Doctoral Dissertation]. McMaster University; 2015. Available from: http://hdl.handle.net/11375/18299

Texas Tech University

10. Osler, Arlo Ray. The Lack of Radio Jet Emissions from 4U 1957+11: New Constraints on Jet Production from Thin Accretion Disks.

Degree: MS, Physics, 2017, Texas Tech University

URL: http://hdl.handle.net/2346/82047

► Radio emission from the jets of soft state stellar mass black hole X-ray binaries is believed to be suppressed by more than a factor of… (more)

Subjects/Keywords: Soft state; Accretion disk; Radio jet emission; 4U 1957+11

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APA (6^th Edition):

Osler, A. R. (2017). The Lack of Radio Jet Emissions from 4U 1957+11: New Constraints on Jet Production from Thin Accretion Disks. (Masters Thesis). Texas Tech University. Retrieved from http://hdl.handle.net/2346/82047

Chicago Manual of Style (16^th Edition):

Osler, Arlo Ray. “The Lack of Radio Jet Emissions from 4U 1957+11: New Constraints on Jet Production from Thin Accretion Disks.” 2017. Masters Thesis, Texas Tech University. Accessed January 17, 2021. http://hdl.handle.net/2346/82047.

MLA Handbook (7^th Edition):

Osler, Arlo Ray. “The Lack of Radio Jet Emissions from 4U 1957+11: New Constraints on Jet Production from Thin Accretion Disks.” 2017. Web. 17 Jan 2021.

Vancouver:

Osler AR. The Lack of Radio Jet Emissions from 4U 1957+11: New Constraints on Jet Production from Thin Accretion Disks. [Internet] [Masters thesis]. Texas Tech University; 2017. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2346/82047.

Council of Science Editors:

Osler AR. The Lack of Radio Jet Emissions from 4U 1957+11: New Constraints on Jet Production from Thin Accretion Disks. [Masters Thesis]. Texas Tech University; 2017. Available from: http://hdl.handle.net/2346/82047

University of the Western Cape

11. Kolwa, Sthabile. The effects of environment on radio-loud AGN activity in Stripe 82 .

Degree: 2016, University of the Western Cape

URL: http://hdl.handle.net/11394/5318

► We investigate the link between environment and radiative accretion efficiency using a sample of 8946 radio-loud AGN detected at 1 − 2 GHz in the… (more)

Subjects/Keywords: Photometry - infrared; Accretion-disk physics; Galaxies; Galaxies – Evolution

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APA (6^th Edition):

Kolwa, S. (2016). The effects of environment on radio-loud AGN activity in Stripe 82 . (Thesis). University of the Western Cape. Retrieved from http://hdl.handle.net/11394/5318

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):

Kolwa, Sthabile. “The effects of environment on radio-loud AGN activity in Stripe 82 .” 2016. Thesis, University of the Western Cape. Accessed January 17, 2021. http://hdl.handle.net/11394/5318.

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

MLA Handbook (7^th Edition):

Kolwa, Sthabile. “The effects of environment on radio-loud AGN activity in Stripe 82 .” 2016. Web. 17 Jan 2021.

Vancouver:

Kolwa S. The effects of environment on radio-loud AGN activity in Stripe 82 . [Internet] [Thesis]. University of the Western Cape; 2016. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11394/5318.

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

Council of Science Editors:

Kolwa S. The effects of environment on radio-loud AGN activity in Stripe 82 . [Thesis]. University of the Western Cape; 2016. Available from: http://hdl.handle.net/11394/5318

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

University of Rochester

12. Li, Shule. Heterogeneous flow in interstellar medium and star formation.

Degree: PhD, 2014, University of Rochester

URL: http://hdl.handle.net/1802/28862

► Almost all interstellar objects contain inherent inhomogeneity. The inhomogeneity can manifest in many different ways, such as the uneven matter distribution in a molecular cloud,… (more)

▼ Almost all interstellar objects contain inherent inhomogeneity. The inhomogeneity can manifest in many different ways, such as the uneven matter distribution in a molecular cloud, or the tangled magnetic field distribution in a Bok globule. The dynamics of interstellar objects is thus often governed by the interaction between astrophysical flows or shocks such as supernova blast waves with inhomogeneous objects. We categorize such interactions as “heterogeneous flows” in general since many of their behaviors can be attributed to the heterogeneous nature of the underlying objects. At the computational physics group of the University of Rochester, we develop the highly sophisticated numerical tool AstroBEAR to study the physics of heterogeneous flows. One such problem is the heat conduction through interfaces between hot and cold magnetized plasmas. Through simulations, we find a simple mathematical relation for the rate of heat conduction as a function of the initial ratio of ordered to tangled field across the interface. The results can be applied to astrophysical objects such as magnetized wind blown bubbles (WBB) around evolved stars. The second problem involves the interaction between shocks and magnetized clumps. Using AstroBEAR, we consider the realistic circumstance in which the field is completely self-contained within the clumps. We find that the clump and magnetic evolution are sensitive to the fraction of magnetic field aligned with versus perpendicular to the shock normal. The relative strength of magnetic pressure and tension in the different field configurations allows us to analytically understand the different cases of postshock evolution. Interstellar heterogeneous flows can also lead to star formation. Based on the shock clump interaction model, star formation can be triggered by compression from wind or supernova driven shock waves that sweep over molecular clouds. This mechanism has been proposed as an explanation for short lived radioactive isotopes (SLRI) in the Solar System. Using AstroBEAR, we for the first time track the long term evolution of the triggering of a 1M⊙ cloud. We also demonstrate that through initial rotation, a circumstellar disk can be formed around such a triggering formed star. Recent progressions in the field of plasma physics, laser technology and instrumentation have led to lab platforms that are scalable to astrophysical objects. These platforms are ideal environments to study the heterogeneous flows directly. An important difference between the astrophysical objects and the lab platform is that the latter involves non-negligible resistivity. We introduce AstroBEAR simulations that investigate the magnetized shock-clump interaction problem under resistive MHD, and answer a crucial question regarding the lab design: in resistive MHD, under what conditions do the shocked behavior of a magnetized clump differ from a non-magnetized one? We find that for R_m ≤ 100, it is impossible to distinguish the two, while for R_m ≥ 1000, the…

Subjects/Keywords: Accretion disc; Heterogeneous flow; Interstellar medium; Magneto-hydrodynamics; Shock; Star formation

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APA (6^th Edition):

Li, S. (2014). Heterogeneous flow in interstellar medium and star formation. (Doctoral Dissertation). University of Rochester. Retrieved from http://hdl.handle.net/1802/28862

Chicago Manual of Style (16^th Edition):

Li, Shule. “Heterogeneous flow in interstellar medium and star formation.” 2014. Doctoral Dissertation, University of Rochester. Accessed January 17, 2021. http://hdl.handle.net/1802/28862.

MLA Handbook (7^th Edition):

Li, Shule. “Heterogeneous flow in interstellar medium and star formation.” 2014. Web. 17 Jan 2021.

Vancouver:

Li S. Heterogeneous flow in interstellar medium and star formation. [Internet] [Doctoral dissertation]. University of Rochester; 2014. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1802/28862.

Council of Science Editors:

Li S. Heterogeneous flow in interstellar medium and star formation. [Doctoral Dissertation]. University of Rochester; 2014. Available from: http://hdl.handle.net/1802/28862

University of Rochester

13. Pecaut, Mark (1975 - ). The star-formation history and accretion disk fraction of the Scorpius-Centaurus OB Association.

Degree: PhD, 2013, University of Rochester

URL: http://hdl.handle.net/1802/27871

► We present a study of the star-formation history and accretion disk fraction of ∼0.6- 1.8 M⊙ stars in the nearest OB Association, Scorpius-Centaurus (Sco-Cen; 10-20… (more)

▼ We present a study of the star-formation history and accretion disk fraction of ∼0.6- 1.8 M⊙ stars in the nearest OB Association, Scorpius-Centaurus (Sco-Cen; 10-20 Myr; 100-200 pc). We have performed a low-resolution spectroscopic survey for new, low-mass K- and M-type members of all three subgroups – Upper Scorpius (US), Upper Centaurus-Lupus (UCL) and Lower Centaurus-Crux (LCC). We find that young, pre-main sequence stars have different intrinsic colors for a given spectral type than their main-sequence (MS) counterparts and therefore MS colors and temperatures are unsuitable for de-reddening the low-mass members of Sco-Cen and placing them on an H-R diagram. Using nearby, pre-MS, unreddened moving groups, we derive a spectral type–intrinsic color sequence appropriate for 5-30 Myr old pre-MS stars, and use synthetic spectral energy distribution fits to infer the proper temperature and bolometric correction scale for these young stars. We use this new pre-MS intrinsic color and temperature calibration to place our ∼150 newly identified members of Sco- Cen on an H-R diagram. We derive isochronal ages for the B-type MS turn-off and the pre-MS F-type, G-Type members and the K- and M-type members of Sco-Cen. We find a Teff -dependent age trend in the K/M-type stars, similar to previous studies of other nearby star-forming regions. Our F- and G-type isochronal ages for Upper Centaurus-Lupus (UCL; 16±2 Myr; < d >=142 pc) and Lower Centaurus-Crux (LCC; 16±3 Myr; < d >=118 pc) are consistent with previous results. However, our results for Upper Scorpius (US; 10±3 Myr; < d >=145 pc) indicate it is a factor of two older than previously thought. Using ∼650 of the pre-MS members of Sco-Cen, we construct an age map, which reveals regions which are systematically younger or older than the mean Sco-Cen age, suggesting that the star-formation history of the three subgroups is more complex than the simple division into three subgroups would imply. Finally, we find a primordial disk fraction for US, UCL and LCC of 9+4 −2%, 5+2 −1% and 3+3 −1%, respectively, for K-type stars decreasing to <19% (95% CL), 2+5 −1%, and 2+4 −1%, respectively, for F-type stars at ∼10 Myr, ∼16 Myr, and ∼16 Myr, respectively.

Subjects/Keywords: Accretion disk fraction; Intrinsic colors; Pre-main sequence stars; Scorpius-Centaurus; Stellar ages; Stellar temperatures

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APA (6^th Edition):

Pecaut, M. (. -. ). (2013). The star-formation history and accretion disk fraction of the Scorpius-Centaurus OB Association. (Doctoral Dissertation). University of Rochester. Retrieved from http://hdl.handle.net/1802/27871

Chicago Manual of Style (16^th Edition):

Pecaut, Mark (1975 - ). “The star-formation history and accretion disk fraction of the Scorpius-Centaurus OB Association.” 2013. Doctoral Dissertation, University of Rochester. Accessed January 17, 2021. http://hdl.handle.net/1802/27871.

MLA Handbook (7^th Edition):

Pecaut, Mark (1975 - ). “The star-formation history and accretion disk fraction of the Scorpius-Centaurus OB Association.” 2013. Web. 17 Jan 2021.

Vancouver:

Pecaut M(-). The star-formation history and accretion disk fraction of the Scorpius-Centaurus OB Association. [Internet] [Doctoral dissertation]. University of Rochester; 2013. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1802/27871.

Council of Science Editors:

Pecaut M(-). The star-formation history and accretion disk fraction of the Scorpius-Centaurus OB Association. [Doctoral Dissertation]. University of Rochester; 2013. Available from: http://hdl.handle.net/1802/27871

University of Michigan

14. Zhu, Zhaohuan. Confronting FU Orionis Outbursts and Pre/transitional Disks: Protostellar/ protoplanetary Disk Structure and Evolution.

Degree: PhD, Astronomy and Astrophysics, 2011, University of Michigan

URL: http://hdl.handle.net/2027.42/86332

► The mechanisms and efficiencies of mass transport in accretion disks can be best constrained by studying their time-dependent behavior. For the first part of my… (more)

▼ The mechanisms and efficiencies of mass transport in accretion disks can be best constrained by studying their time-dependent behavior. For the first part of my thesis work, I studied outbursts of rapid accretion in protostellar disks. This was motivated by observations of the FU Orionis objects, which are young stellar objects with a sudden increase of their brightness. I first constructed disk radiative transfer models to compare with Spitzer observations, and found that the outburst disk region extends to scales of an AU or more, with the inferred limits on the viscosity parameter alpha~0.02-0.2. I further analyzed the multi-wavelength high resolution spectra to show the outbursting disk follows Keplerian rotation. I next studied the thermal structure of the disk which leads us to propose that the outburst is due to the thermal activation of the magnetorotational instability (MRI) at ~AU scales by the gravitational instability (GI). We carried out both analytic studies and 2-Dimensional radiationhydrodyanmic simulations to study the outbursts and constrain the activation of the MRI. Then I extended this work by constructing simplified 1-dimensional time-dependent simulations with infall from the protostellar envelope to study protostellar disk formation and long term evolution. I found that the outbursting behavior of the protostellar disks during the infall phase alleviates the so called "luminosity problem", and the layered accretion at the later phase leads to a massive dead zone where planet formation is favored. In the second part of my thesis work, I studied protoplanetary disks with gaps and holes-so called "pretransitional and transitional disks",- to study planet formation in young disks. I have studied gap opening by dynamically-interacting multiple giant planets with two-dimensional hydrodynamic simulations. I found that even with as many as four giant planets, additional substantial dust depletion (e.g. growth) is required to explain these gaps and holes, which sheds light on the early planet formation environment. Advisors/Committee Members: Hartmann, Lee William (committee member), Adams, Fred C. (committee member), Calvet, Nuria P. (committee member), Gammie, Charles Forbes (committee member), Monnier, John D. (committee member).

Subjects/Keywords: Star Formation; Planet Formation; Episodic Accretion; Outburst; Magnetorotational Instability; Planet Disk Interaction; Astronomy; Science

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APA (6^th Edition):

Zhu, Z. (2011). Confronting FU Orionis Outbursts and Pre/transitional Disks: Protostellar/ protoplanetary Disk Structure and Evolution. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/86332

Chicago Manual of Style (16^th Edition):

Zhu, Zhaohuan. “Confronting FU Orionis Outbursts and Pre/transitional Disks: Protostellar/ protoplanetary Disk Structure and Evolution.” 2011. Doctoral Dissertation, University of Michigan. Accessed January 17, 2021. http://hdl.handle.net/2027.42/86332.

MLA Handbook (7^th Edition):

Zhu, Zhaohuan. “Confronting FU Orionis Outbursts and Pre/transitional Disks: Protostellar/ protoplanetary Disk Structure and Evolution.” 2011. Web. 17 Jan 2021.

Vancouver:

Zhu Z. Confronting FU Orionis Outbursts and Pre/transitional Disks: Protostellar/ protoplanetary Disk Structure and Evolution. [Internet] [Doctoral dissertation]. University of Michigan; 2011. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2027.42/86332.

Council of Science Editors:

Zhu Z. Confronting FU Orionis Outbursts and Pre/transitional Disks: Protostellar/ protoplanetary Disk Structure and Evolution. [Doctoral Dissertation]. University of Michigan; 2011. Available from: http://hdl.handle.net/2027.42/86332

Université de Bordeaux I

15. Trova, Audrey. Gravité des systèmes verticalement homogènes : applications aux disques astrophysiques : Gravity of vertically homogeneous systems : application to astrophysical disks.

Degree: Docteur es, Astrophysique, 2013, Université de Bordeaux I

URL: http://www.theses.fr/2013BOR14902

► La gravitation joue un rôle important dans de nombreux domaines de l'astrophysique : elle assure notamment la cohésion et la stabilité des planètes, des étoiles… (more)

▼ La gravitation joue un rôle important dans de nombreux domaines de l'astrophysique : elle assure notamment la cohésion et la stabilité des planètes, des étoiles et des disques. Elle est aussi motrice dans le processus d'effondrement de structure et conduit, dès lors qu'un moment cinétique initial est significatif, à la formation d'un disque.Ma thèse est consacrée à l'étude des disques de gaz, et plus particulièrement à la description du potentiel et du champ de gravité qu'ils génèrent dans l'espace et sur eux-mêmes (l'auto-gravitation). Bien que la force de Newton soit connue depuis longtemps, la détermination des interactions auto-gravitantes reste difficile, en particulier lorsque l'on s'écarte significativement de la sphéricité. La principale difficulté tient dans la divergence hyperbolique du Noyau de Green 1/(r'-r) et nécessite un traitement propre. L'approche théorique est intéressante car elle fournit de nouveaux outils (techniques numériques, formules approchées, etc...) qui peuvent aider à produire des solutions de référence et à améliorer les simulations numériques.Dans une première partie, nous introduisons le sujet, les notions et les bases essentielles. Le chapitre 1 est consacré à une présentation succinte du contexte scientifique et aux motivations de notre travail. Dans le chapitre 2, nous reproduisons dans ces grandes lignes le cheminement conduisant au développement multipolaire, à partir de l'équation de Poisson et de la formule intégrale de Newton. Il s'agit de l'une des méthodes les plus classiques permettant d'obtenir le potentiel gravitationnel d'un corps. Les deux systèmes de coordonnées les plus utilisées sont mis en avant : sphériques et cylindriques. A travers quelques exemples, nous montrons les limites de cette approche, en particulier dans le cas de l'auto-gravité des disques.Dans une deuxième partie, nous abordons le vif du sujet. Le chapitre 3 présente l'approche basée sur les intégrales elliptiques que nous retrouverons dans l'ensemble du manuscrit (cas général d'abord, puis cas axi-symétrique). Dans le chapitre 4, nous établissons un premier résultat concernant le noyau de Green dans des systèmes axi-symétriques et verticalement homogènes : une forme alternative et régulière du noyau, quelque soit le point de l'espace. Nous avons exploité cette nouvelle formule pour déduire une bonne approximation du potentiel des disques géométriquement minces, des anneaux et des systèmes faiblement étendus en rayon. Ceci fait l'objet du chapitre 5.Dans une troisième partie, nous étudions les effets de bords sur la composante verticale du champ de gravité, gz, causés par un disque mince axi-symétrique. Le chapitre 6 est dédié à l'approximation de Paczynski pacz78, qui permet traditionnellement d'exprimer le champ comme une fonction linéaire de la densité de surface locale. Cette approximation n'est en fait strictement valide que dans le cas du modèle du "plan infini", loin d'un disque réaliste. Près du bord externe des disques où la gravité décroit, l'approximation de Paczynski s'avère assez… Advisors/Committee Members: Huré, Jean-Marc (thesis director), Hersant, Franck (thesis director).

Subjects/Keywords: Gravitation; Disque d'accretion; Methode analytique; Methode numérique; Gravitation; Accretion disk; Analytical method; Numerical method

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APA (6^th Edition):

Trova, A. (2013). Gravité des systèmes verticalement homogènes : applications aux disques astrophysiques : Gravity of vertically homogeneous systems : application to astrophysical disks. (Doctoral Dissertation). Université de Bordeaux I. Retrieved from http://www.theses.fr/2013BOR14902

Chicago Manual of Style (16^th Edition):

Trova, Audrey. “Gravité des systèmes verticalement homogènes : applications aux disques astrophysiques : Gravity of vertically homogeneous systems : application to astrophysical disks.” 2013. Doctoral Dissertation, Université de Bordeaux I. Accessed January 17, 2021. http://www.theses.fr/2013BOR14902.

MLA Handbook (7^th Edition):

Trova, Audrey. “Gravité des systèmes verticalement homogènes : applications aux disques astrophysiques : Gravity of vertically homogeneous systems : application to astrophysical disks.” 2013. Web. 17 Jan 2021.

Vancouver:

Trova A. Gravité des systèmes verticalement homogènes : applications aux disques astrophysiques : Gravity of vertically homogeneous systems : application to astrophysical disks. [Internet] [Doctoral dissertation]. Université de Bordeaux I; 2013. [cited 2021 Jan 17]. Available from: http://www.theses.fr/2013BOR14902.

Council of Science Editors:

Trova A. Gravité des systèmes verticalement homogènes : applications aux disques astrophysiques : Gravity of vertically homogeneous systems : application to astrophysical disks. [Doctoral Dissertation]. Université de Bordeaux I; 2013. Available from: http://www.theses.fr/2013BOR14902

16. Belyaev, Mikhail. Dynamics of Thin Astrophysical Boundary Layers .

Degree: PhD, 2013, Princeton University

URL: http://arks.princeton.edu/ark:/88435/dsp01qn59q405t

► We study the modal structure and angular momentum transport mechanisms of astrophysical boundary layers. We focus on the case where the accretion disk extends all… (more)

▼ We study the modal structure and angular momentum transport mechanisms of astrophysical boundary layers. We focus on the case where the accretion disk extends all the way to surface of the star and the boundary layer is thin in comparison with the stellar radius. Such a scenario is applicable, for example, to weakly magnetized neutron stars and white dwarfs, for which the strength of the magnetic field outside the star is too small to disrupt the disk and funnel matter to the poles. Within the boundary layer, material rotating at the Keplerian velocity within the disk slows down to the rotational velocity inside the star. This generates intense velocity gradients and makes the boundary layer susceptible to shear instabilities. By performing a linear stability analysis for the simplified case of a plane-parallel, compressible shear layer, we argue that astrophysical boundary layers are unstable to the sonic instability. This instability is part of a more general class of acoustic instabilities that includes the Papaloizou-Pringle instability. We confirm the predictions of our linear stability analysis by running a suite of simulations in 2D and 3D, with and without stratification, and with and without magnetic field. In our numerical experiments, we find that acoustic modes excited by the sonic instability persist even in the nonlinear regime. We explain the morphological properties and derive analytic formulas for the pattern speed of these acoustic modes. Our work has significant implications for semianalytic models describing the structure and spectral emission from boundary layers. Typically, these models adopt a local, effective viscosity prescription for the angular momentum transport. However, in our simulations we find that angular momentum transport in the boundary layer is facilitated by acoustic modes. In this scenario, accreting material inside the boundary layer loses angular momentum to sound waves that propagate into both the star and the disk. Since transport of angular momentum by waves is inherently nonlocal, our work invites the construction of new phenomenological models of the boundary layer in which angular momentum is transported by waves rather than by an anomalous viscosity. Advisors/Committee Members: Rafikov, Roman R (advisor), Stone, James M (advisor).

Subjects/Keywords: accretion; angular momentum; disk; MRI; star; waves

…Density Gap in the Inner Disk and Accretion onto the Star . . . . . . . . . . 160 6.2 Angular… …accretion disk theory. However, there has been surprisingly little work on the dynamics of the… …1978). For B∗ < B∗,crit , the accretion disk will extend all the way to the surface of… …of the disk. If the accretion rate is high enough, it is also possible for material to… …Angular Momentum Transport to Mass Accretion Rate . . . . . . 115 5 Effect of Stratification…

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APA (6^th Edition):

Belyaev, M. (2013). Dynamics of Thin Astrophysical Boundary Layers . (Doctoral Dissertation). Princeton University. Retrieved from http://arks.princeton.edu/ark:/88435/dsp01qn59q405t

Chicago Manual of Style (16^th Edition):

Belyaev, Mikhail. “Dynamics of Thin Astrophysical Boundary Layers .” 2013. Doctoral Dissertation, Princeton University. Accessed January 17, 2021. http://arks.princeton.edu/ark:/88435/dsp01qn59q405t.

MLA Handbook (7^th Edition):

Belyaev, Mikhail. “Dynamics of Thin Astrophysical Boundary Layers .” 2013. Web. 17 Jan 2021.

Vancouver:

Belyaev M. Dynamics of Thin Astrophysical Boundary Layers . [Internet] [Doctoral dissertation]. Princeton University; 2013. [cited 2021 Jan 17]. Available from: http://arks.princeton.edu/ark:/88435/dsp01qn59q405t.

Council of Science Editors:

Belyaev M. Dynamics of Thin Astrophysical Boundary Layers . [Doctoral Dissertation]. Princeton University; 2013. Available from: http://arks.princeton.edu/ark:/88435/dsp01qn59q405t

17. Rosin, Mark. Instabilities and transport in magnetized plasmas.

Degree: PhD, 2011, University of Cambridge

URL: http://www.dspace.cam.ac.uk/handle/1810/237241https://www.repository.cam.ac.uk/bitstream/1810/237241/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/3/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/5/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/6/MarkThesis.pdf.jpg

► In a magnetized plasma, naturally occurring pressure anisotropies facilitate in- stabilities that are expected to modify the transport properties of the system. In this thesis… (more)

▼ In a magnetized plasma, naturally occurring pressure anisotropies facilitate in- stabilities that are expected to modify the transport properties of the system. In this thesis we examine two such instabilities and, where appropriate, their effects on transport. First we consider the collisional (fluid) magnetized magnetorotational instability (MRI) in the presence of the Braginskii viscosity. We conduct a global linear analysis of the instability in a galactic rotation profile for three magnetic field configurations: purely azimuthal, purely vertical and slightly pitched. Our analysis, numerical and asymptotic, shows that the first two represent singular configurations where the Braginskii viscosity’s primary role is dissipative and the maximum growth rate is proportional to the Reynolds number when this is small. For a weak pitched field, the Braginskii viscosity is destabilising and when its effects dominate over the Lorentz force, the growth rate of the MRI can be up to 2√2 times faster than the inviscid limit. If the field is strong, an over-stability develops and both the real and imaginary parts of the frequency increase with the coefficient of the viscosity. Second, in the context of the ICM of galaxy clusters, we consider the pressure-anisotropy-driven firehose instability. The linear instability is fast (∼ ion cyclotron period) and small-scale (ion Larmor radius ρi) and so fluid theory is inapplicable. We determine its nonlinear evolution in an ab initio kinetic calculation (for parallel gradients only). We use a particular physical asymptotic ordering to derive a closed nonlinear equation for the firehose turbulence, which we solve. We find secular (∝ t) growth of magnetic fluctuations and a k−∥3 spectrum, starting at scales >~ ρi. When a parallel ion heat flux is present, the parallel firehose instability mutates into the new gyrothermal instability. Its nonlinear evolution also involves secular magnetic energy growth, but its spectrum is eventually dominated by modes with a maximal scale ∼ρilT/λmfp,(lT is the parallel temperature gradient scale). Throughout we discuss implications for modelling, transport and other areas of magnetized plasma physics.

Subjects/Keywords: Plasma; Magnetic field; Fluid; Kinetic; Magnetized; Firehose instability; Magnetorotational instatbility; MRI; Transport; Galaxy clusters; Accretion disc; MHD

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APA (6^th Edition):

Rosin, M. (2011). Instabilities and transport in magnetized plasmas. (Doctoral Dissertation). University of Cambridge. Retrieved from http://www.dspace.cam.ac.uk/handle/1810/237241https://www.repository.cam.ac.uk/bitstream/1810/237241/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/3/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/5/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/6/MarkThesis.pdf.jpg

Chicago Manual of Style (16^th Edition):

Rosin, Mark. “Instabilities and transport in magnetized plasmas.” 2011. Doctoral Dissertation, University of Cambridge. Accessed January 17, 2021. http://www.dspace.cam.ac.uk/handle/1810/237241https://www.repository.cam.ac.uk/bitstream/1810/237241/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/3/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/5/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/6/MarkThesis.pdf.jpg.

MLA Handbook (7^th Edition):

Rosin, Mark. “Instabilities and transport in magnetized plasmas.” 2011. Web. 17 Jan 2021.

Vancouver:

Rosin M. Instabilities and transport in magnetized plasmas. [Internet] [Doctoral dissertation]. University of Cambridge; 2011. [cited 2021 Jan 17]. Available from: http://www.dspace.cam.ac.uk/handle/1810/237241https://www.repository.cam.ac.uk/bitstream/1810/237241/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/3/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/5/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/6/MarkThesis.pdf.jpg.

Council of Science Editors:

Rosin M. Instabilities and transport in magnetized plasmas. [Doctoral Dissertation]. University of Cambridge; 2011. Available from: http://www.dspace.cam.ac.uk/handle/1810/237241https://www.repository.cam.ac.uk/bitstream/1810/237241/2/license.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/3/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/5/MarkThesis.pdf.txt ; https://www.repository.cam.ac.uk/bitstream/1810/237241/6/MarkThesis.pdf.jpg

University of Cambridge

18. Rosin, Mark. Instabilities and transport in magnetized plasmas.

Degree: PhD, 2011, University of Cambridge

URL: https://doi.org/10.17863/CAM.16100 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541846

► In a magnetized plasma, naturally occurring pressure anisotropies facilitate instabilities that are expected to modify the transport properties of the system. In this thesis we… (more)

▼ In a magnetized plasma, naturally occurring pressure anisotropies facilitate instabilities that are expected to modify the transport properties of the system. In this thesis we examine two such instabilities and, where appropriate, their effects on transport. First we consider the collisional (fluid) magnetized magnetorotational instability (MRI) in the presence of the Braginskii viscosity. We conduct a global linear analysis of the instability in a galactic rotation profile for three magnetic field configurations: purely azimuthal, purely vertical and slightly pitched. Our analysis, numerical and asymptotic, shows that the first two represent singular configurations where the Braginskii viscosity's primary role is dissipative and the maximum growth rate is proportional to the Reynolds number when this is small. For a weak pitched field, the Braginskii viscosity is destabilising and when its effects dominate over the Lorentz force, the growth rate of the MRI can be up to 2√2 times faster than the inviscid limit. If the field is strong, an over-stability develops and both the real and imaginary parts of the frequency increase with the coefficient of the viscosity. Second, in the context of the ICM of galaxy clusters, we consider the pressure-anisotropy-driven firehose instability. The linear instability is fast (~ ion cyclotron period) and small-scale (ion Larmor radius ρi) and so fluid theory is inapplicable. We determine its nonlinear evolution in an ab initio kinetic calculation (for parallel gradients only). We use a particular physical asymptotic ordering to derive a closed nonlinear equation for the firehose turbulence, which we solve. We find secular (α t) growth of magnetic fluctuations and a k-||3 spectrum, starting at scales >~ ρi. When a parallel ion heat flux is present, the parallel firehose instability mutates into the new gyrothermal instability. Its nonlinear evolution also involves secular magnetic energy growth, but its spectrum is eventually dominated by modes with a maximal scale ~ρilT/λmfp,(lT is the parallel temperature gradient scale). Throughout we discuss implications for modelling, transport and other areas of magnetized plasma physics.

Subjects/Keywords: 523.01; Plasma; Magnetic field; Fluid; Kinetic; Magnetized; Firehose instability; Magnetorotational instatbility; MRI; Transport; Galaxy clusters; Accretion disc; MHD

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

APA (6^th Edition):

Rosin, M. (2011). Instabilities and transport in magnetized plasmas. (Doctoral Dissertation). University of Cambridge. Retrieved from https://doi.org/10.17863/CAM.16100 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541846

Chicago Manual of Style (16^th Edition):

Rosin, Mark. “Instabilities and transport in magnetized plasmas.” 2011. Doctoral Dissertation, University of Cambridge. Accessed January 17, 2021. https://doi.org/10.17863/CAM.16100 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541846.

MLA Handbook (7^th Edition):

Rosin, Mark. “Instabilities and transport in magnetized plasmas.” 2011. Web. 17 Jan 2021.

Vancouver:

Rosin M. Instabilities and transport in magnetized plasmas. [Internet] [Doctoral dissertation]. University of Cambridge; 2011. [cited 2021 Jan 17]. Available from: https://doi.org/10.17863/CAM.16100 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541846.

Council of Science Editors:

Rosin M. Instabilities and transport in magnetized plasmas. [Doctoral Dissertation]. University of Cambridge; 2011. Available from: https://doi.org/10.17863/CAM.16100 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541846

19. Epitropakis, Anastasios. Variability studies of the iron line emission in AGN.

Degree: 2017, University of Crete (UOC); Πανεπιστήμιο Κρήτης

URL: http://hdl.handle.net/10442/hedi/40954

►

To this day, the physics and geometry of the inner-most region in active galactic nuclei (AGN) are largely unknown. According to the currently-accepted paradigm, the… (more)

▼

To this day, the physics and geometry of the inner-most region in active galactic nuclei (AGN) are largely unknown. According to the currently-accepted paradigm, the inner-most region consists of a super-massive black hole (BH) surrounded by an accretion disc. Perhaps the only way of indirectly probing this region is to study the highly variable X-ray emission of AGN. This X-ray emission is thought to consist of a power-law continuum component from a primary X-ray source, plus “reprocessed” continuum emission by the accretion disc.This scenario predicts that reprocessed disc emission should also vary in response to the intrinsically variable continuum emission, but with a delay (this is known as “X-ray reverberation”). The search for correlations, including delays, between light curves in different energy bands has revealed evidence in support of the X-ray reverberation picture, although the results are mostly “hand-waving.” This is mainly because the statistical properties of the available tools, i.e. the “time-lag spectrum” and “intrinsic coherence function,” are unknown.In my work I developed, for the first time, prescriptions for reliably and accurately calculating time-lag and intrinsic coherence estimates. I then applied these prescriptions to estimate the time-lags and intrinsic coherence between X-ray light curves in different energy bands, for a sample of ten X-ray bright and highly variable AGN. To this end, I downloaded and reduced all available XMM-Newton archival data for these sources. The results of my study regarding the time-lags and intrinsic coherence of my sample are summarised as follows: (a) The “iron line vs. continuum” (i.e. 5-7 vs. 2-4 keV) time-lags, which have the most widely-accepted reverberation origin, are consistent with a “point-like” X-ray source located a few gravitational radii above the BH. However, it is not possible to constrain other important parameters such as the BH mass and spin, or the inclination angle of the system. (b) The low-frequency “continuum” time-lags have a universal energy- and frequency-dependence, and scale approximately with the square root of the Eddington accretion rate. (c) The intrinsic coherence has a universal energy- and frequency-dependence, although it scales neither with the BH mass, nor with the Eddington accretion rate.Result (a) is the best that can be done with current data. It is also unlikely to significantly improve in the future, since that would require a substantial improvement in the data quality (e.g. many more XMM-Newton observations). Results (b) and (c) are broadly consistent with popular AGN X-ray variability models, although detailed theoretical predictions need to be compared to my results in order to constrain the models.

Η φυσική και η γεωμετρία της εσωτερικής περιοχής των ενεργών γαλαξιακών πυρήνων (ΕΓΠ) παραπέμενουν ακόμα εν πολλοίς άγνωστες. Σύμφωνα με τη σημερινά αποδεκτή εικόνα, η εσωτερική περιοχή αποτελείται από μία υπέρμαζη μελανή οπή (ΜΟ) που περιβάλλεται από έναν δίσκο προσαύξησης. Ο μόνος τρόπος να ερευνηθεί έμμεσα…

Subjects/Keywords: Δίσκοι προσαύξησης; Ακτίνες-Χ; Σχετικότητα; Ανάλυση δεδομένων; Ανάκτηση δορυφορικών δεδομένων; Ανάλυση δορυφορικών εικόνων; Δορυφορικά δεδομένα; Στατιστικές μέθοδοι; Στατιστικές τεχνικές; Στατιστική βελτιστοποίηση; Αστρονομία; Αστροφυσική; Υπολογιστική αστροφυσική; Accretion; Accretion disc; Accretion disks; X-rays; Relativity; Data analysis; Sattelite data; Statistical analysis; Statistical data analysis; Astronomy; Astrophysics; Computational astrophysics

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

APA (6^th Edition):

Epitropakis, A. (2017). Variability studies of the iron line emission in AGN. (Thesis). University of Crete (UOC); Πανεπιστήμιο Κρήτης. Retrieved from http://hdl.handle.net/10442/hedi/40954

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):

Epitropakis, Anastasios. “Variability studies of the iron line emission in AGN.” 2017. Thesis, University of Crete (UOC); Πανεπιστήμιο Κρήτης. Accessed January 17, 2021. http://hdl.handle.net/10442/hedi/40954.

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

MLA Handbook (7^th Edition):

Epitropakis, Anastasios. “Variability studies of the iron line emission in AGN.” 2017. Web. 17 Jan 2021.

Vancouver:

Epitropakis A. Variability studies of the iron line emission in AGN. [Internet] [Thesis]. University of Crete (UOC); Πανεπιστήμιο Κρήτης; 2017. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/10442/hedi/40954.

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

Council of Science Editors:

Epitropakis A. Variability studies of the iron line emission in AGN. [Thesis]. University of Crete (UOC); Πανεπιστήμιο Κρήτης; 2017. Available from: http://hdl.handle.net/10442/hedi/40954

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

20. Cridland, Alexander. Connecting the Chemical Composition of Planetary Atmospheres with Planet Formation.

Degree: PhD, 2017, McMaster University

URL: http://hdl.handle.net/11375/22005

►

What sets the observable chemical composition of exoplanetary atmospheres? The available chemical abundance of the planet's natal protoplanetary disk gas will have a deciding role… (more)

▼

What sets the observable chemical composition of exoplanetary atmospheres? The available chemical abundance of the planet's natal protoplanetary disk gas will have a deciding role in the bulk abundance of the atmosphere very early in the planet's life. While late accretion of ices and inter-atmosphere physical processing can change the observable chemical abundances. We have developed a theoretical model which connects the chemical and physical evolution of an accretion disk with the growth of a young planet to predict the bulk chemical abundance of the planetary atmosphere that is inherited from the disk. We assess what variation in atmospheric chemical abundances are attributed to different planet formation histories. We find differences in the relative abundances of primary nitrogen carriers NH₃ and N₂ depending on {\it when} the planet accreted its gas. Early (t<1 Myr) accreters predominately accreted warmer gas which tend to have its nitrogen in NH₃, while later protoplanets accrete colder, more N₂ dominated gas. Furthermore we compute the carbon-to-oxygen ratio (C/O) for each planets, which is used to infer {\it where} a planet forms in its accretion disk. We find that each of our planets accrete their gas very close to the water ice line, thereby accreting `pristine' gas with C/O_planet exactly matching its host star. We extend our results by tuning our initial disk parameters to reproduce the properties of the HL Tau disk. We produce three models that span the range of measured gas masses, and one model which studies a UV quiet system. We generally find that planet formation is efficient enough to produce a Jupiter-massed planet within the predicted 1 Myr age of the disk. We find a correspondence between the radial locations of ice lines within our astrochemical model and the set of observed dust gaps in the HL Tau system.

Thesis

Doctor of Philosophy (PhD)

Advisors/Committee Members: Pudritz, Ralph, Physics and Astronomy.

Subjects/Keywords: Planet formation; Astrochemistry; Accretion disk physics; Dust physics; Planetary atmospheres

…what follows we will discuss the theoretical and observational aspects of accretion disk… …relies on the assumption that the disk is accretion material in what is known as a steady disk… …ﬂow. For a steady disk, Σ has no explicit time dependence, which forces the mass accretion… …evolving accretion disk (LyndenBell & Pringle, 1974) acts as a heating source, and… …Goldreich (1997) derived the midplane temperature and SED for a ﬂared accretion disk…

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APA (6^th Edition):

Cridland, A. (2017). Connecting the Chemical Composition of Planetary Atmospheres with Planet Formation. (Doctoral Dissertation). McMaster University. Retrieved from http://hdl.handle.net/11375/22005

Chicago Manual of Style (16^th Edition):

Cridland, Alexander. “Connecting the Chemical Composition of Planetary Atmospheres with Planet Formation.” 2017. Doctoral Dissertation, McMaster University. Accessed January 17, 2021. http://hdl.handle.net/11375/22005.

MLA Handbook (7^th Edition):

Cridland, Alexander. “Connecting the Chemical Composition of Planetary Atmospheres with Planet Formation.” 2017. Web. 17 Jan 2021.

Vancouver:

Cridland A. Connecting the Chemical Composition of Planetary Atmospheres with Planet Formation. [Internet] [Doctoral dissertation]. McMaster University; 2017. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11375/22005.

Council of Science Editors:

Cridland A. Connecting the Chemical Composition of Planetary Atmospheres with Planet Formation. [Doctoral Dissertation]. McMaster University; 2017. Available from: http://hdl.handle.net/11375/22005

McMaster University

21. Hasegawa, Yasuhiro. Planet Traps in Protoplanetary Disks and the Formation and Evolution of Planetary Systems.

Degree: PhD, 2012, McMaster University

URL: http://hdl.handle.net/11375/12569

► One of the most fundamental problems in theories of planet formation in protoplanetary disks is planetary migration that arises from resonant, tidal interactions of… (more)

▼ One of the most fundamental problems in theories of planet formation in protoplanetary disks is planetary migration that arises from resonant, tidal interactions of forming planets with the natal disks. This rapid inward migration, also known as type I migration, leads to the well-known problem that its timescale is about two orders of magnitude shorter than the typical disk lifetime, so that (proto)planets plunge into the host stars within the disk lifetime. This provides a huge hurdle for understanding the statistical properties of observed extra solar planets that now amount to more than 700. In this thesis, we focus on one of the most general properties of protoplanetary disks - inhomogeneities. A large amount of theoretical and observational work currently suggests that protoplanetary disks are most likely to possess several kinds of inhomogeneities. Planetary migration is highly sensitive to the disk properties such as the surface density and temperature of disks, and the sensitivity leads to the formation of trapping sites for rapid type I migration at disk inhomogeneities. These local sites capturing planets undergoing migration are referred to as planet traps. We perform both analytical and numerical studies for exploring formation mechanisms of planet traps at disk inhomogeneities and their consequences for the formation and evolution of planetary systems. We focus on three kinds of the disk inhomogeneities: dead zones, ice lines, and transitions of heat sources in protoplanetary disks we refer to as heat transitions. Dead zones are an inevitable consequence of disk turbulence originating from magnetorotational instabilities (MRIs) that take place in (partially) ionized disks threaded by weak magnetic fields. One of the fundamental properties of the dead zone is a low level of turbulence there, which is the outcome of the high density, preventing the region from being ionized due to X-rays from the central stars and cosmic rays. Ice lines are formed due to low disk temperatures which lead to condensation of specific molecules there. Heat transitions arise as a consequence of the switching of the dominant heating process from viscous heating to stellar irradiation as the distance to the host stars increases. We summarize our major findings. 1) rapid dust settling arising in dead zones leaves a dusty wall at the outer edge of the dead zones beyond which the disks are quite turbulent, so that dust is fully mixed with the gas. Efficient heating of the wall by stellar irradiation and the subsequent backward heating of the dead zones by the wall result in a positive temperature gradient in the dead zones. This inversion in the temperature profiles leads to outward migration there. 2) Any protoplanetary disk is likely to possess up to three types of planet traps that are specified by characteristic disk radii (dead zone, ice line and heat transition traps). Disk evolution, driven by disk viscosity, lowers both the accretion rate and surface density of gas and moves traps inward at different rates.… Advisors/Committee Members: Pudrtiz, Ralph, Physics and Astronomy.

Subjects/Keywords: accretion disks; turbulence; planets and satellites: formation; protoplanetary disks; Planet-disk interactions; Astrophysics and Astronomy; Physical Sciences and Mathematics; Astrophysics and Astronomy

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

APA (6^th Edition):

Hasegawa, Y. (2012). Planet Traps in Protoplanetary Disks and the Formation and Evolution of Planetary Systems. (Doctoral Dissertation). McMaster University. Retrieved from http://hdl.handle.net/11375/12569

Chicago Manual of Style (16^th Edition):

Hasegawa, Yasuhiro. “Planet Traps in Protoplanetary Disks and the Formation and Evolution of Planetary Systems.” 2012. Doctoral Dissertation, McMaster University. Accessed January 17, 2021. http://hdl.handle.net/11375/12569.

MLA Handbook (7^th Edition):

Hasegawa, Yasuhiro. “Planet Traps in Protoplanetary Disks and the Formation and Evolution of Planetary Systems.” 2012. Web. 17 Jan 2021.

Vancouver:

Hasegawa Y. Planet Traps in Protoplanetary Disks and the Formation and Evolution of Planetary Systems. [Internet] [Doctoral dissertation]. McMaster University; 2012. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/11375/12569.

Council of Science Editors:

Hasegawa Y. Planet Traps in Protoplanetary Disks and the Formation and Evolution of Planetary Systems. [Doctoral Dissertation]. McMaster University; 2012. Available from: http://hdl.handle.net/11375/12569

22. Malmrose, Michael Paul. Thermal emission signatures in non-thermal blazars.

Degree: PhD, Astronomy, 2016, Boston University

URL: http://hdl.handle.net/2144/19757

► Blazars, a subclass of active galactic nuclei with powerful relativistic plasma jets, are among the most luminous and violently variable objects in the universe. They… (more)

▼ Blazars, a subclass of active galactic nuclei with powerful relativistic plasma jets, are among the most luminous and violently variable objects in the universe. They emit radiation across the entire electromagnetic spectrum, and often change in brightness over the course of hours or days. Different emission mechanisms are necessary in order to explain the observed flux in different frequency ranges. In the ultraviolet-optical- infrared regime these include components that arise from: 1) polarized synchrotron radiation emanating from a powerful parsec-scale jet flowing from near the central accreting black hole, 2) a multi-temperature accretion disk emitting thermal radia- tion, and 3) an optically thick dusty torus located several parsecs from the central engine that absorbs and re-emits, at infrared wavelengths, radiation originating in the accretion disk. The goal of this study is to determine the relative importance of these spectral components in the spectra of blazars. I use data from the Spitzer Space Telescope in order to search for the presence of the dusty torus surrounding four blazars, as well as to determine its luminosity and temperature. In two of the observed sources, 1222+216 and CTA102, I determine that the torus can be modeled as a 1200 K blackbody emitting at nearly 10 46 erg s −1 . Furthermore, I determine the relative variability of the accretion disk of a sample of blazars by using spec- tropolarimetry observations to separate the optical-UV spectrum into a polarized viiicomponent, consisting of radiation described by a power-law F ν ∝ ν −α , and an ac- cretion disk which consists of a thin disk described by the power-law F disk ∝ ν 1/3 plus a hot-spot of variable temperature. The spectra of several blazars are explained by a version of this model in which the thin disk component is held constant, while the blackbody varies on timescales of approximately years resulting with a flux of the blackbody component comparable to the power-law disk component. I find that variations in the emission from the hot-spot occurs approximately within 100 days of γ-ray variations.

Subjects/Keywords: Astronomy; AGN; Blazars; Dust; Accretion disk; Supermassive black holes

…temperature accretion disk emitting thermal radiation, and 3) an optically thick dusty torus… …wavelengths, radiation originating in the accretion disk. The goal of this study is to determine the… …law Fν ∝ ν −α , and an accretion disk which consists of a thin disk described by the power… …Ray Variability of a Sample of Blazars Compared to Variability of the Accretion Disk 153 6.1… …accretion disk model modiﬁed to include a hot blackbody . . . . . . . . . . . . . . . . . . 80…

9 more images…

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APA (6^th Edition):

Malmrose, M. P. (2016). Thermal emission signatures in non-thermal blazars. (Doctoral Dissertation). Boston University. Retrieved from http://hdl.handle.net/2144/19757

Chicago Manual of Style (16^th Edition):

Malmrose, Michael Paul. “Thermal emission signatures in non-thermal blazars.” 2016. Doctoral Dissertation, Boston University. Accessed January 17, 2021. http://hdl.handle.net/2144/19757.

MLA Handbook (7^th Edition):

Malmrose, Michael Paul. “Thermal emission signatures in non-thermal blazars.” 2016. Web. 17 Jan 2021.

Vancouver:

Malmrose MP. Thermal emission signatures in non-thermal blazars. [Internet] [Doctoral dissertation]. Boston University; 2016. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2144/19757.

Council of Science Editors:

Malmrose MP. Thermal emission signatures in non-thermal blazars. [Doctoral Dissertation]. Boston University; 2016. Available from: http://hdl.handle.net/2144/19757

George Mason University

23. Makeev, Andrey. Formation of the Power Density Spectrum in the Accreting Compact X-Ray Objects .

Degree: 2010, George Mason University

URL: http://hdl.handle.net/1920/6026

► One of the remarkable phenomena, characterizing both Galactic and extra-Galactic Xray binary systems, is the substantial variability of a photon ux, detectable in a very… (more)

▼ One of the remarkable phenomena, characterizing both Galactic and extra-Galactic Xray binary systems, is the substantial variability of a photon ux, detectable in a very broad range of timescales. For instance, the accretion ow near a black hole event horizon can produce X-ray variability on a millisecond timescale. At the same time aperiodic changes from the extended accretion disk formed around the same black hole can occur on timescales of order of several months to years. A complex structure, involving high and low frequency nearly periodic oscillations and aperiodic features, observed in X-ray lightcurves, is the subject of intensive studies. The characteristic quantities, extracted from temporal analysis, carry speci c physical meaning and contain direct observational information about dynamics of the accreting X-ray source. It is the established fact that X-ray spectral and timing properties are tightly correlated. Combined together, the photon energy spectrum and the power density spectrum analyses, form a powerful framework that brings up the complete (in the energy/space domain) picture of the physical processes at work in the accreting system. Simultaneous study of spectral and timing characteristics allows for comprehensive probing of the geometry of accretion ows, reliable identi cation of the type of an X-ray source (black hole vs neutron star), constraining mass, size, and spin of accreting stellar-mass compact objects. Up until now there is no self-consistent physical model of the formation and evolution of the X-ray variability. This leaves a relative freedom in interpretation of the characteristic quantities obtained from the timing analysis. The current work aims at development of the physical alternative to the commonplace ad hoc description of the Fourier power density spectrum of X-ray timing signal. In the following study we employ the di usion theory to directly solve for the X-ray luminosity uctuations. The basic underlying physical assumption is that the observed variability of Xray luminosity originates as the result of local uctuations of the accretion rate, at all radii in the disk, that di usively propagate outward. Energy dissipation (and X-ray emission) occurs in a narrow, shock-like region, called the transition layer, where the Keplerian ow becomes non-Keplerian in order to adjust itself to the slowly-rotating surface of a neutron star or the innermost stable orbit around a black hole. The X-ray time signal from the transition region, as seen by a remote observer, is obtained by integrating over the emission zone. The signal's power spectrum is then calculated and analyzed. Our di usion model of the power spectrum formation operates with parameters that are physical characteristics of the accretion ow: the di usion time scale, the Reynolds number (which is connected to the viscosity -parameter), Keplerian and magnetosonic quasi-periodic oscillation frequencies, radial size of the transition layer, and viscosity index, related to the… Advisors/Committee Members: Becker, Peter A (advisor).

Subjects/Keywords: accretion disk; power spectrum; x-ray binary; x-ray luminosity; x-ray variability

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APA (6^th Edition):

Makeev, A. (2010). Formation of the Power Density Spectrum in the Accreting Compact X-Ray Objects . (Thesis). George Mason University. Retrieved from http://hdl.handle.net/1920/6026

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):

Makeev, Andrey. “Formation of the Power Density Spectrum in the Accreting Compact X-Ray Objects .” 2010. Thesis, George Mason University. Accessed January 17, 2021. http://hdl.handle.net/1920/6026.

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

MLA Handbook (7^th Edition):

Makeev, Andrey. “Formation of the Power Density Spectrum in the Accreting Compact X-Ray Objects .” 2010. Web. 17 Jan 2021.

Vancouver:

Makeev A. Formation of the Power Density Spectrum in the Accreting Compact X-Ray Objects . [Internet] [Thesis]. George Mason University; 2010. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/1920/6026.

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

Council of Science Editors:

Makeev A. Formation of the Power Density Spectrum in the Accreting Compact X-Ray Objects . [Thesis]. George Mason University; 2010. Available from: http://hdl.handle.net/1920/6026

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

Louisiana State University

24. Megevand, Miguel. Matter sources interacting with a black hole: dynamics and observable signatures.

Degree: PhD, Physical Sciences and Mathematics, 2009, Louisiana State University

URL: etd-11032009-142431 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2763

► Dynamical systems involving black holes are one of the most promising sources of detectable gravitational waves. Additionally, one expects strong electromagnetic signals whenever matter sources… (more)

Subjects/Keywords: black hole; shocks; kicks; scalar field; galaxy; gravitational waves; accretion disk

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

APA (6^th Edition):

Megevand, M. (2009). Matter sources interacting with a black hole: dynamics and observable signatures. (Doctoral Dissertation). Louisiana State University. Retrieved from etd-11032009-142431 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2763

Chicago Manual of Style (16^th Edition):

Megevand, Miguel. “Matter sources interacting with a black hole: dynamics and observable signatures.” 2009. Doctoral Dissertation, Louisiana State University. Accessed January 17, 2021. etd-11032009-142431 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2763.

MLA Handbook (7^th Edition):

Megevand, Miguel. “Matter sources interacting with a black hole: dynamics and observable signatures.” 2009. Web. 17 Jan 2021.

Vancouver:

Megevand M. Matter sources interacting with a black hole: dynamics and observable signatures. [Internet] [Doctoral dissertation]. Louisiana State University; 2009. [cited 2021 Jan 17]. Available from: etd-11032009-142431 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2763.

Council of Science Editors:

Megevand M. Matter sources interacting with a black hole: dynamics and observable signatures. [Doctoral Dissertation]. Louisiana State University; 2009. Available from: etd-11032009-142431 ; https://digitalcommons.lsu.edu/gradschool_dissertations/2763

25. Schilbach, Tyson. Accretion Disk Contributions to the Diffuse Neutrino Background.

Degree: MS, Department of Physics, 2018, University of Guelph

URL: https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14280

► Predictions for AD neutrino detection at Super Kamiokande and Hyper Kamiokande are made. Concepts related to the diffuse neutrino background for accretion disks are introduced.… (more)

Subjects/Keywords: Physics; Nuclear; Astrophysics; Neutrino; Diffuse Background; Accretion Disk

…work will focus on three accretion disk sources. Neutron star - neutron star mergers, black… …accretion disk neutrinos as it is already calibrated for supernova neutrinos. The primary range of… …neutrino spectra for a single accretion disk is reviewed. From here, two red shifts are… …detection in a Earth-based water Cherenkov detector can be found. 2.1 Disk Models Accretion… …thermodynamical properties of the accretion disk relative to distance from the black hole. The model…

10 more images…

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

APA (6^th Edition):

Schilbach, T. (2018). Accretion Disk Contributions to the Diffuse Neutrino Background. (Masters Thesis). University of Guelph. Retrieved from https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14280

Chicago Manual of Style (16^th Edition):

Schilbach, Tyson. “Accretion Disk Contributions to the Diffuse Neutrino Background.” 2018. Masters Thesis, University of Guelph. Accessed January 17, 2021. https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14280.

MLA Handbook (7^th Edition):

Schilbach, Tyson. “Accretion Disk Contributions to the Diffuse Neutrino Background.” 2018. Web. 17 Jan 2021.

Vancouver:

Schilbach T. Accretion Disk Contributions to the Diffuse Neutrino Background. [Internet] [Masters thesis]. University of Guelph; 2018. [cited 2021 Jan 17]. Available from: https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14280.

Council of Science Editors:

Schilbach T. Accretion Disk Contributions to the Diffuse Neutrino Background. [Masters Thesis]. University of Guelph; 2018. Available from: https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14280

26. Isogai, Keisuke. Observational Research on Dwarf Novae: Superoutburst, Evolution, and Development of a Classification Method Using Gaia DR2 .

Degree: 2019, Kyoto University

URL: http://hdl.handle.net/2433/242610

Subjects/Keywords: accretion disk; cataclysmic variable; dwarf nova; superoutburst; AM CVn star

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

APA (6^th Edition):

Isogai, K. (2019). Observational Research on Dwarf Novae: Superoutburst, Evolution, and Development of a Classification Method Using Gaia DR2 . (Thesis). Kyoto University. Retrieved from http://hdl.handle.net/2433/242610

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):

Isogai, Keisuke. “Observational Research on Dwarf Novae: Superoutburst, Evolution, and Development of a Classification Method Using Gaia DR2 .” 2019. Thesis, Kyoto University. Accessed January 17, 2021. http://hdl.handle.net/2433/242610.

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

MLA Handbook (7^th Edition):

Isogai, Keisuke. “Observational Research on Dwarf Novae: Superoutburst, Evolution, and Development of a Classification Method Using Gaia DR2 .” 2019. Web. 17 Jan 2021.

Vancouver:

Isogai K. Observational Research on Dwarf Novae: Superoutburst, Evolution, and Development of a Classification Method Using Gaia DR2 . [Internet] [Thesis]. Kyoto University; 2019. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2433/242610.

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

Council of Science Editors:

Isogai K. Observational Research on Dwarf Novae: Superoutburst, Evolution, and Development of a Classification Method Using Gaia DR2 . [Thesis]. Kyoto University; 2019. Available from: http://hdl.handle.net/2433/242610

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

The Ohio State University

27. Poindexter, Shawn David. Sharpening The Tools of Gravitational Microlensing.

Degree: PhD, Astronomy, 2009, The Ohio State University

URL: http://rave.ohiolink.edu/etdc/view?acc_num=osu1258766992

► We attempt to identify all microlensing parallax events for which the parallax fit improves ΔΧ² > 100 relative to a standard microlensing model. We… (more)

▼ We attempt to identify all microlensing parallax events for which the parallax fit improves ΔΧ² > 100 relative to a standard microlensing model. We outline a procedure to identify three types of discrete degeneracies and find many new degenerate solutions in 16 previously published and 6 unpublished events. The lens of event OGLE-2003-BLG-84 may be a Jupiter-mass free-floating planet candidate based on a weak 3σ detection of finite-source effects. These events were examined for xallarap, which can mimic parallax. We find that 23% of these events are strongly affected by xallarap. The mid-IR flux ratios of the two images of the gravitationally lensed quasar HE 1104-1805 show no wavelength dependence to within 3% across 3.6-8.0 microns, no time dependence over 6 months and agree with the broad emission line flux ratios. This indicates that the mid-IR emission likely comes from scales large enough to be little affected by microlensing and that there is little differential extinction between the images. We measure a revised time-delay between these two images. We also observed uncorrelated variations of ~ 0.05 mag/yr^-1 which we attribute to microlensing of the optical emission from the accretion disk. The optical colors have also changed significantly in the sense that image A is now redder than image B, rather than bluer as it was in 1993. Based on the microlensing variability of the two-image gravitational lens HE 1104-1805 observed between 0.4 and 8 microns, we have measured the size and wavelength-dependent structure of the quasar accretion disk. Modeled as a power law in temperature, we measure a B-band half-light radius of R = 6.7(+6.2)(-3.2)x10¹⁵ cm (68% CL) and a logarithmic slope of 0.61(+0.21)(-0.17) (68% CL) for our standard model with a logarithmic prior on the disk size. Both the scale and the slope are consistent with simple thin disk models. The observed fluxes favor a slightly shallower temperature profile. Using 11-years of OGLE V-band photometry of Q2237+0305, we measure the transverse velocity of the lens galaxy and the mean mass of its stars. We measure the inclination i of the accretion disk to be cos i > 0.63 at 68% confidence. Very edge on (cos i < 0.34) solutions are ruled out at 95% confidence. For the first time, we fully include the random motions of the stars in the lens galaxy in the analysis of the light curves. We find the best fit transverse velocity of the lens galaxy is ~ 420 km/s to the Northeast. There is no strong correlation between the direction of motion of the lens galaxy and the orientation of the disk. The mean stellar mass is 0.37(+1.07)(-0.26) solar masses after including a well-defined velocity prior. We measure the V-band radius of the accretion disk. We also show for the first time that analyzing subsets of a microlensing light curve, in this case the first and second halves of the OGLE V-band light curve, give mutually consistent physical results. Advisors/Committee Members: Kochanek, Christopher (Advisor).

Subjects/Keywords: Astronomy; gravitational lensing; microlensing; parallax; xallarap; quasar microlensing; accretion disk

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

APA (6^th Edition):

Poindexter, S. D. (2009). Sharpening The Tools of Gravitational Microlensing. (Doctoral Dissertation). The Ohio State University. Retrieved from http://rave.ohiolink.edu/etdc/view?acc_num=osu1258766992

Chicago Manual of Style (16^th Edition):

Poindexter, Shawn David. “Sharpening The Tools of Gravitational Microlensing.” 2009. Doctoral Dissertation, The Ohio State University. Accessed January 17, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1258766992.

MLA Handbook (7^th Edition):

Poindexter, Shawn David. “Sharpening The Tools of Gravitational Microlensing.” 2009. Web. 17 Jan 2021.

Vancouver:

Poindexter SD. Sharpening The Tools of Gravitational Microlensing. [Internet] [Doctoral dissertation]. The Ohio State University; 2009. [cited 2021 Jan 17]. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1258766992.

Council of Science Editors:

Poindexter SD. Sharpening The Tools of Gravitational Microlensing. [Doctoral Dissertation]. The Ohio State University; 2009. Available from: http://rave.ohiolink.edu/etdc/view?acc_num=osu1258766992

University of Texas – Austin

28. Bayless, Amanda Jo. Accretion disks in low-mass X-ray binaries in ultraviolet and optical wavelengths.

Degree: PhD, Astronomy, 2010, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2010-08-1727

► We present new models for two low-mass X-ray binaries (LMXB), 4U 1822-371 and V1408 Aql (= 4U 1957+115). The eclipsing LMXB 4U 1822-371 is the… (more)

▼ We present new models for two low-mass X-ray binaries (LMXB), 4U 1822-371 and V1408 Aql (= 4U 1957+115). The eclipsing LMXB 4U 1822-371 is the prototypical accretion disk corona (ADC) system. We have obtained new time-resolved UV spectroscopy of 4U 1822-371 with the Advanced Camera for Surveys/Solar Blind Channel on the Hubble Space Telescope and new V- and J- band photometry with the 1.3-m SMARTS telescope at Cerro Tololo Inter-American Observatory. We use the new data to construct the UV/optical spectral energy distribution of 4U 1822-371 and its orbital light curve in the UV, V , and J bands. We derive an improved ephemeris for the optical eclipses and confirm that the orbital period is changing rapidly, indicating extremely high rates of mass flow in the system; and we show that the accretion disk in the system has a strong wind with projected radial velocities up to 4400 km s⁻¹. We show that the disk has a vertically extended, optically thick component at optical wavelengths. This component extends almost to the edge of the disk and has a height equal to ~0.5 of the disk radius. As it has a low brightness temperature, we identify it as the optically thick base of the disk wind, not as the optical counterpart of the ADC. Like previous models of 4U 1822-371, ours needs a tall obscuring wall near the edge of the accretion disk, but we interpret the wall as a layer of cooler material at the base of the disk wind, not as a tall, luminous disk rim. V1408 Aql is a black hole candidate. We have obtained new optical photometry of this system in 2008 and 2009 with the Argos photometer on the 2.1-m Otto Struve telescope and optical spectra with the low resolution spectrometer on the Hobby Eberly telescope. From the data we derive an improved optical orbital ephemeris and a new geometric model for the system. The model uses only a simple thin disk without the need for a warped disk or a large disk rim. The orbital variation is produced by the changing aspect of the irradiated secondary star with orbital phase. The new model leaves the orbital inclination unconstrained and allows for inclinations as low as 20 degrees. The spectra is largely featureless continuum with He II and occasionally H[alpha] emission lines, and an absorption line from Na D. The lines are highly variable in strength and wavelength, but the variations do not correlate with orbital phase. Advisors/Committee Members: Robinson, Edward Lewis, 1945- (advisor), Hynes, Robert I. (committee member), Milosavljevic, Milos (committee member), Sneden, Christopher (committee member), Wheeler, Craig (committee member).

Subjects/Keywords: X-ray binaries; Eclipsing binaries; Compact objects; Accretion disk corona

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APA (6^th Edition):

Bayless, A. J. (2010). Accretion disks in low-mass X-ray binaries in ultraviolet and optical wavelengths. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2010-08-1727

Chicago Manual of Style (16^th Edition):

Bayless, Amanda Jo. “Accretion disks in low-mass X-ray binaries in ultraviolet and optical wavelengths.” 2010. Doctoral Dissertation, University of Texas – Austin. Accessed January 17, 2021. http://hdl.handle.net/2152/ETD-UT-2010-08-1727.

MLA Handbook (7^th Edition):

Bayless, Amanda Jo. “Accretion disks in low-mass X-ray binaries in ultraviolet and optical wavelengths.” 2010. Web. 17 Jan 2021.

Vancouver:

Bayless AJ. Accretion disks in low-mass X-ray binaries in ultraviolet and optical wavelengths. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2010. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2152/ETD-UT-2010-08-1727.

Council of Science Editors:

Bayless AJ. Accretion disks in low-mass X-ray binaries in ultraviolet and optical wavelengths. [Doctoral Dissertation]. University of Texas – Austin; 2010. Available from: http://hdl.handle.net/2152/ETD-UT-2010-08-1727

29. Nauta, Michiel Doede. Two-dimensional vortices and accretion disks.

Degree: 2000, University Utrecht

URL: https://dspace.library.uu.nl/handle/1874/639 ; URN:NBN:NL:UI:10-1874-639 ; 1874/639 ; URN:NBN:NL:UI:10-1874-639 ; https://dspace.library.uu.nl/handle/1874/639

► Observations show that there are disks around certain stars that slowly rain down on the central (compact) object: accretion disks. The rate of depletion of… (more)

▼ Observations show that there are disks around certain stars that slowly rain down on the central (compact) object: accretion disks. The rate of depletion of the disk might be slow but is still larger than was expected on theoretical grounds. That is why it has been suggested that the disks are turbulent. Because the disk is thin and rotating this turbulence might be related to two-dimensional (2D) turbulence which is characterized by energy transfers towards small wave numbers and the formation of 2D-vortices. This hypothesis is investigated in this thesis by numerical simulations. After an introduction, the numerical algorithm that was inplemented is discussed together with its relation to an accretion disk. It performs well under the absence of discontinuities. The code is used to study 2D-turbulence under the influence of background rotation with compressibility and a shearing background flow. The first is found to be of little consequence but the shear flow alters 2D-turbulence siginificantly. Only prograde vortices of enough strength are able to withstand the shear flow. The size of the vortices in the cross stream direction is also found to be smaller than the equivalent of the thickness of an accretion disk. These circulstances imply that the assumption of two-dimensionality is questionable so that 2D-vortices might not abound in accretion disks. However, the existence of such vortices is not ruled out and one such a cortex is studied in detail in chapter 4. The internal structure of the vortex is well described by a balance between Coriolis, centrifugal and pressure forces. The vortex is also accompanied by two spiral compressible waves. These are not responsible for the azimuthal drift of the vortex, which results from secondary vortices, but they might be related to the small radial drift that is observed. Radial drift leads to accretion but it is not very efficient. Multiple vortex interactions are the topic of tha last chapter and though interesting the increase in accretion grows only linearly with the number of vortices.

Subjects/Keywords: accretion disk; VORTEX; geophysical fluid dynamics; two-dimensional turbulence; shocks; angular momentum transport

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

APA (6^th Edition):

Nauta, M. D. (2000). Two-dimensional vortices and accretion disks. (Doctoral Dissertation). University Utrecht. Retrieved from https://dspace.library.uu.nl/handle/1874/639 ; URN:NBN:NL:UI:10-1874-639 ; 1874/639 ; URN:NBN:NL:UI:10-1874-639 ; https://dspace.library.uu.nl/handle/1874/639

Chicago Manual of Style (16^th Edition):

Nauta, Michiel Doede. “Two-dimensional vortices and accretion disks.” 2000. Doctoral Dissertation, University Utrecht. Accessed January 17, 2021. https://dspace.library.uu.nl/handle/1874/639 ; URN:NBN:NL:UI:10-1874-639 ; 1874/639 ; URN:NBN:NL:UI:10-1874-639 ; https://dspace.library.uu.nl/handle/1874/639.

MLA Handbook (7^th Edition):

Nauta, Michiel Doede. “Two-dimensional vortices and accretion disks.” 2000. Web. 17 Jan 2021.

Vancouver:

Nauta MD. Two-dimensional vortices and accretion disks. [Internet] [Doctoral dissertation]. University Utrecht; 2000. [cited 2021 Jan 17]. Available from: https://dspace.library.uu.nl/handle/1874/639 ; URN:NBN:NL:UI:10-1874-639 ; 1874/639 ; URN:NBN:NL:UI:10-1874-639 ; https://dspace.library.uu.nl/handle/1874/639.

Council of Science Editors:

Nauta MD. Two-dimensional vortices and accretion disks. [Doctoral Dissertation]. University Utrecht; 2000. Available from: https://dspace.library.uu.nl/handle/1874/639 ; URN:NBN:NL:UI:10-1874-639 ; 1874/639 ; URN:NBN:NL:UI:10-1874-639 ; https://dspace.library.uu.nl/handle/1874/639

30. E. Ragusa. THE EVOLUTION OF BINARY SYSTEMS IN GASEOUS ENVIRONMENTS.

Degree: 2018, Università degli Studi di Milano

URL: http://hdl.handle.net/2434/604177

► Systems where a binary, that is two gravitationally bound objects orbiting their centre of mass, interacts with the surrounding gas or dust are extremely common… (more)

Subjects/Keywords: Protoplanetary discs; Planet formation; Black hole binaries; Satellite-disc interaction; Accretion discs; satellite migration; eccentricity evolution; non-axisymmetric features; Settore FIS/05 - Astronomia e Astrofisica

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

APA (6^th Edition):

Ragusa, E. (2018). THE EVOLUTION OF BINARY SYSTEMS IN GASEOUS ENVIRONMENTS. (Thesis). Università degli Studi di Milano. Retrieved from http://hdl.handle.net/2434/604177

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):

Ragusa, E.. “THE EVOLUTION OF BINARY SYSTEMS IN GASEOUS ENVIRONMENTS.” 2018. Thesis, Università degli Studi di Milano. Accessed January 17, 2021. http://hdl.handle.net/2434/604177.

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

MLA Handbook (7^th Edition):

Ragusa, E.. “THE EVOLUTION OF BINARY SYSTEMS IN GASEOUS ENVIRONMENTS.” 2018. Web. 17 Jan 2021.

Vancouver:

Ragusa E. THE EVOLUTION OF BINARY SYSTEMS IN GASEOUS ENVIRONMENTS. [Internet] [Thesis]. Università degli Studi di Milano; 2018. [cited 2021 Jan 17]. Available from: http://hdl.handle.net/2434/604177.

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

Council of Science Editors:

Ragusa E. THE EVOLUTION OF BINARY SYSTEMS IN GASEOUS ENVIRONMENTS. [Thesis]. Università degli Studi di Milano; 2018. Available from: http://hdl.handle.net/2434/604177

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

Open Access Theses and Dissertations