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Radiative Relativistic Magnetohydrodynamic Simulations of Neutron Star Column Accretion- [electronic resource]
Radiative Relativistic Magnetohydrodynamic Simulations of Neutron Star Column Accretion- [electronic resource]
상세정보
- 자료유형
- 학위논문파일 국외
- 최종처리일시
- 20240214101513
- ISBN
- 9798380616928
- DDC
- 530
- 저자명
- Zhang, Lizhong.
- 서명/저자
- Radiative Relativistic Magnetohydrodynamic Simulations of Neutron Star Column Accretion - [electronic resource]
- 발행사항
- [S.l.]: : University of California, Santa Barbara., 2023
- 발행사항
- Ann Arbor : : ProQuest Dissertations & Theses,, 2023
- 형태사항
- 1 online resource(270 p.)
- 주기사항
- Source: Dissertations Abstracts International, Volume: 85-04, Section: B.
- 주기사항
- Advisor: Blaes, Omer.
- 학위논문주기
- Thesis (Ph.D.)--University of California, Santa Barbara, 2023.
- 사용제한주기
- This item must not be sold to any third party vendors.
- 초록/해제
- 요약Accretion onto a strongly magnetized neutron star at a sufficiently high mass accretion rate results in the formation of a radiation pressure-supported columnar structure near the polar regions. In this region, the accretion inflow is magnetically constrained and shocked above the stellar surface. Below the shock, the accretion column liberates most of the accretion power through the sideways radiation emission in a so-called `fan-beam' pattern, in contrast to the `pencil-beam' emission where radiation leaves directly from the top of the column. The physics of the accretion column plays a defining role in understanding the observations of accretion-powered X-ray pulsars, including pulsating ultraluminous X-ray sources (ULXs). The observed pulsations arise from the misalignment between the anisotropic radiation emission and the spin axis of the rotating neutron star. We perform radiative relativistic MHD simulations to study the nonlinear dynamics of the accretion column. The column structure is extremely dynamical and exhibits kHz quasi-periodic oscillations. The existence of the photon bubble instability is identified in simulated accretion columns but proved to be not responsible for triggering the oscillatory behaviors. Instead, the oscillations originate from the inability of the system to resupply heat and locally balance the sideways cooling. When the oscillation amplitude is sufficiently large, the emergent radiation can exhibit hybrid fan- and pencil-beam patterns. The column structure is very sensitive to the shock geometry, which directly determines the cooling efficiency. A more diverging geometry of the accretion column can provide more heat support through PdV work. The time-averaged column structures from the simulations can be approximately reproduced by a 1D stationary model, given the correction for the actual 2D mound shape of the time-averaged column. The increase in magnetic opacity with temperature below the radiative shock may introduce an additional unstable mechanism in the dynamics of the accretion column. Pair production can boost the opacity above ~4 x 108 K near the base of the column, which is likely to introduce further dynamical effects. To further investigate these problems, we propose an extension of the current numerical framework by incorporating magnetic polarization into the radiation module.
- 일반주제명
- Physics.
- 일반주제명
- Astrophysics.
- 일반주제명
- Computational physics.
- 키워드
- Instabilities
- 키워드
- Radiation
- 키워드
- Stars
- 키워드
- X-rays
- 키워드
- Dynamics
- 키워드
- Neutron
- 키워드
- Binaries
- 기타저자
- University of California, Santa Barbara Physics
- 기본자료저록
- Dissertations Abstracts International. 85-04B.
- 기본자료저록
- Dissertation Abstract International
- 전자적 위치 및 접속
- 로그인 후 원문을 볼 수 있습니다.
MARC
008240612s2023 us |||||||||||||||c||eng d■001000016933976
■00520240214101513
■006m o d
■007cr#unu||||||||
■020 ▼a9798380616928
■035 ▼a(MiAaPQ)AAI30568624
■040 ▼aMiAaPQ▼cMiAaPQ
■0820 ▼a530
■1001 ▼aZhang, Lizhong.
■24510▼aRadiative Relativistic Magnetohydrodynamic Simulations of Neutron Star Column Accretion▼h[electronic resource]
■260 ▼a[S.l.]:▼bUniversity of California, Santa Barbara. ▼c2023
■260 1▼aAnn Arbor :▼bProQuest Dissertations & Theses, ▼c2023
■300 ▼a1 online resource(270 p.)
■500 ▼aSource: Dissertations Abstracts International, Volume: 85-04, Section: B.
■500 ▼aAdvisor: Blaes, Omer.
■5021 ▼aThesis (Ph.D.)--University of California, Santa Barbara, 2023.
■506 ▼aThis item must not be sold to any third party vendors.
■520 ▼aAccretion onto a strongly magnetized neutron star at a sufficiently high mass accretion rate results in the formation of a radiation pressure-supported columnar structure near the polar regions. In this region, the accretion inflow is magnetically constrained and shocked above the stellar surface. Below the shock, the accretion column liberates most of the accretion power through the sideways radiation emission in a so-called `fan-beam' pattern, in contrast to the `pencil-beam' emission where radiation leaves directly from the top of the column. The physics of the accretion column plays a defining role in understanding the observations of accretion-powered X-ray pulsars, including pulsating ultraluminous X-ray sources (ULXs). The observed pulsations arise from the misalignment between the anisotropic radiation emission and the spin axis of the rotating neutron star. We perform radiative relativistic MHD simulations to study the nonlinear dynamics of the accretion column. The column structure is extremely dynamical and exhibits kHz quasi-periodic oscillations. The existence of the photon bubble instability is identified in simulated accretion columns but proved to be not responsible for triggering the oscillatory behaviors. Instead, the oscillations originate from the inability of the system to resupply heat and locally balance the sideways cooling. When the oscillation amplitude is sufficiently large, the emergent radiation can exhibit hybrid fan- and pencil-beam patterns. The column structure is very sensitive to the shock geometry, which directly determines the cooling efficiency. A more diverging geometry of the accretion column can provide more heat support through PdV work. The time-averaged column structures from the simulations can be approximately reproduced by a 1D stationary model, given the correction for the actual 2D mound shape of the time-averaged column. The increase in magnetic opacity with temperature below the radiative shock may introduce an additional unstable mechanism in the dynamics of the accretion column. Pair production can boost the opacity above ~4 x 108 K near the base of the column, which is likely to introduce further dynamical effects. To further investigate these problems, we propose an extension of the current numerical framework by incorporating magnetic polarization into the radiation module.
■590 ▼aSchool code: 0035.
■650 4▼aPhysics.
■650 4▼aAstrophysics.
■650 4▼aComputational physics.
■653 ▼aInstabilities
■653 ▼aRadiation
■653 ▼aStars
■653 ▼aX-rays
■653 ▼aDynamics
■653 ▼aNeutron
■653 ▼aBinaries
■690 ▼a0605
■690 ▼a0596
■690 ▼a0216
■71020▼aUniversity of California, Santa Barbara▼bPhysics.
■7730 ▼tDissertations Abstracts International▼g85-04B.
■773 ▼tDissertation Abstract International
■790 ▼a0035
■791 ▼aPh.D.
■792 ▼a2023
■793 ▼aEnglish
■85640▼uhttp://www.riss.kr/pdu/ddodLink.do?id=T16933976▼nKERIS▼z이 자료의 원문은 한국교육학술정보원에서 제공합니다.
■980 ▼a202402▼f2024
