The vertical structure of T Tauri accretion discs

ABSTRACT Whether tidal disruption events circularize or accrete directly as highly eccentric discs is the subject of current research and appears to depend sensitively on the disc thermodynamics. One aspect of this problem that has not received much attention is that a highly eccentric disc must have a strong, non-hydrostatic variation of the disc scale height around each orbit. As a complement to numerical simulations carried out by other groups, we investigate the dynamical structure of TDE discs using the non-linear theory of eccentric accretion discs. In particular, we study the variation of physical quantities around each elliptical orbit, taking into account the dynamical vertical structure, as well as viscous dissipation and radiative cooling. The solutions include a structure similar to the nozzle-like structure seen in simulations. We find evidence for the existence of the thermal instability in highly eccentric discs dominated by radiation pressure. For thermally stable solutions many of our models indicate a failure of the α-prescription for turbulent stresses. We discuss the consequences of our results for the structure of eccentric TDE discs.

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Alpha Beta Discs

International Astronomical Union Colloquium ◽

10.1017/s0252921100090187 ◽

1983 ◽

Vol 72 ◽

pp. 55-67

Author(s):

G.T. Bath ◽

A.C. Edwards ◽

V.J. Mantle

Keyword(s):

Mass Transfer ◽

Vertical Structure ◽

Accretion Discs ◽

Time Dependent ◽

Simple Method ◽

Dwarf Nova ◽

Physical Conditions ◽

Alpha Beta ◽

Symbiotic Binaries

Following earlier work of Lynden-Bell & Pringle (1974) and Lightman (1974a, 1974b), Bath & Pringle (1981) have presented a simple method for studying the time-dependent evolution of viscous accretion discs. These models are axisymmetrlc, with the vertical structure reduced to integrated averages of local physical conditions. Published work examines models of dwarf nova eruptions driven by mass transfer bursts (Bath & Pringle 1981 – Paper I), eruptions produced by global viscous changes within the disc (Bath & Pringle 1982a Paper II), and the time-dependent properties of giant discs in symbiotic binaries (Bath & Pringle 1982b – Paper III).

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X-Ray Heated Accretion Discs Around Stellar Mass Black Holes

International Astronomical Union Colloquium ◽

10.1017/s0252921100152479 ◽

2004 ◽

Vol 194 ◽

pp. 200-201

Author(s):

Ivan Hubeny ◽

Dayal T. Wickramasinghe

Keyword(s):

Black Holes ◽

Black Hole ◽

Vertical Structure ◽

Black Body ◽

Incident Radiation ◽

Accretion Discs ◽

Distribution Models ◽

Solar Mass ◽

X Ray ◽

Low Mass

We investigate the effects of irradiation on the vertical structure of accretion discs around black holes and its impact on the emergent energy distribution. Models are presented for a 10 Solar mass black hole in a low mass X-ray binary assuming a black body spectrum for the incident radiation. We show that for a disc annulus at a given radius, the spectra become increasingly distorted as the incident flux increases relative to the viscously generated heating flux in the disc. Significant effects are apparent for rings even at distances of ~ 10,000 Schwarzschild radii from the black hole for realistic dilution factors.

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Magnetic fields of T Tauri stars and inner accretion discs

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319003740 ◽

2018 ◽

Vol 14 (A30) ◽

pp. 121-121

Author(s):

Jean-Francois Donati

Keyword(s):

Magnetic Fields ◽

Large Scale ◽

Near Infrared ◽

High Sensitivity ◽

T Tauri Stars ◽

Accretion Discs ◽

High Resolution Spectroscopy ◽

T Tauri ◽

Low Mass ◽

The Impact

AbstractMagnetic fields play a key role in the early life of stars and their planets, as they form from collapsing dense cores that progressively flatten into large-scale accretion discs and eventually settle as young suns orbited by planetary systems. Pre-main-sequence phases, in which central protostars feed from surrounding planet-forming accretion discs, are especially crucial for understanding how worlds like our Solar System are born.Magnetic fields of low-mass T Tauri stars (TTSs) are detected through high-resolution spectroscopy and spectropolarimetry (e.g., Johns Krull 2007), whereas their large-scale topologies can be inferred from time series of Zeeman signatures using tomographic techniques inspired from medical imaging (Donati & Landstreet 2009). Large-scale fields of TTSs are found to depend on the internal structure of the newborn star, allowing quantitative models of how TTSs magnetically interact with their inner accretion discs, and the impact of this interaction on the subsequent stellar evolution (e.g., Romanova et al. 2002, Zanni & Ferreira 2013).With its high sensitivity to magnetic fields, SPIRou, the new near-infrared spectropolarimeter installed in 2018 at CFHT (Donati et al. 2018), should yield new advances in the field, especially for young embedded class-I protostars, thereby bridging the gap with radio observations.

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Magnetic field dragging and the vertical structure of thin accretion discs

Monthly Notices of the Royal Astronomical Society ◽

10.1046/j.1365-8711.2000.03449.x ◽

2000 ◽

Vol 315 (4) ◽

pp. 762-766 ◽

Cited By ~ 10

Author(s):

D. Shalybkov ◽

G. Rudiger

Keyword(s):

Magnetic Field ◽

Vertical Structure ◽

Accretion Discs

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Analytical model for the local vertical structure of thin accretion discs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3052 ◽

2020 ◽

Vol 499 (3) ◽

pp. 3571-3577

Author(s):

J Fukue

Keyword(s):

Radiation Pressure ◽

Vertical Structure ◽

Error Function ◽

Approximate Solutions ◽

Angular Speed ◽

Accretion Discs ◽

Analytical Relation ◽

Viscous Heating ◽

Heating Model ◽

Analytical Relations

ABSTRACT We derive several analytical relations and approximate solutions for the local vertical structure of viscous thin accretion discs. Under the alpha prescription, when the viscous heating is proportional to the gas pressure p, we derive the analytical relation between the radiative flux F and the radiation pressure P: (F/F0)2 = [1 − (P/Pc)5/4]/[1 − (P0/Pc)5/4], where the subscript 0 means the value at the surface and the subscript c is the value at the disc centre. Both F and P are approximately integrated to yield the well-known uniform heating model. In this case, furthermore, the height z and density ρ are approximately fitted as a function of the optical depth τ. When the viscous heating is proportional to the radiation pressure P and the disc is almost isothermal, the flux F is proportional to z as F = (3/2)αΩPz, where α and Ω are the alpha parameter and angular speed, respectively. In this case, moreover, the height and density are analytically solved and expressed as $z=(\sqrt{2}c_{\rm T}/\Omega) {\rm erf}^{-1}(1-\tau /\tau _{\rm c})$ and ρ = ρcexp { − [erf−1(1 − τ/τc)]2}, cT being the isothermal sound speed, and erf−1 the inverse of the error function.

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