What does it take to launch self-confined jets from astrophysical accretion discs?

AbstractIn this contribution we first briefly review our current knowledge on the physics of accretion discs driving self-confined jets. It will be shown that a large scale magnetic field is expected to thread the innermost disc regions, giving rise to a transition from an outer standard accretion disc to an inner jet emitting disc. We then report new progresses on the theory of star-disc interaction, allowing to explain the formation of accretion funnel flows with stellar dipole fields consistent with observational constraints. Such a connection is now not only probed by modern observations but it is also requested for spinning down protostars, which are known to be both actively accreting and contracting. This spin down most probably relies on the angular momentum removal by ejection. Two such scenarios will be addressed here, namely “accretion-powered stellar winds” (Matt & Pudritz 2005) and “Reconnection X-winds” (Ferreira, Pelletier & Appl 2000). The latter can slow down a protostar on time scales shorter or comparable to the embedded phase. It will be shown that these two scenarios are not incompatible and that transitions from one to another may even occur as they mainly depend on the stellar dynamo.

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Accretion Discs in AGN, Viscosity and Structure of Accretion Disks

EAS Publications Series ◽

10.1051/eas:2001008 ◽

2001 ◽

Vol 1 ◽

pp. 53-61

Author(s):

J.-M. Hure ◽

D. Richard

Keyword(s):

Accretion Disks ◽

Accretion Discs

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Vertical structure of accretion discs in LMXB

The multi-messenger astronomy: gamma-ray bursts, search for electromagnetic counterparts to neutrino events and gravitational waves. Proceedings of the International Conference. ◽

10.26119/sao.2019.1.35553 ◽

2019 ◽

Author(s):

A. Tavleev ◽

K. Malanchev ◽

G. Lipunova

Keyword(s):

Vertical Structure ◽

Accretion Discs

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The Physics of Accretion Discs, Winds and Jets in Tidal Disruption Events

Space Science Reviews ◽

10.1007/s11214-020-00747-x ◽

2021 ◽

Vol 217 (1) ◽

Author(s):

Jane Lixin Dai ◽

Giuseppe Lodato ◽

Roseanne Cheng

Keyword(s):

Accretion Discs ◽

Tidal Disruption

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Dynamical structure of highly eccentric discs with applications to tidal disruption events

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3459 ◽

2020 ◽

Vol 500 (3) ◽

pp. 4110-4125

Author(s):

Elliot M Lynch ◽

Gordon I Ogilvie

Keyword(s):

Thermal Instability ◽

Vertical Structure ◽

Scale Height ◽

Accretion Discs ◽

Radiative Cooling ◽

Dynamical Structure ◽

Tidal Disruption ◽

The Subject ◽

Stable Solutions ◽

Physical Quantities

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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No-z Model for Magnetic Fields of Different Astrophysical Objects and Stability of the Solutions

Data ◽

10.3390/data6010004 ◽

2021 ◽

Vol 6 (1) ◽

pp. 4

Author(s):

Evgeny Mikhailov ◽

Daniela Boneva ◽

Maria Pashentseva

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Large Scale ◽

Point Of View ◽

Accretion Discs ◽

Wide Range ◽

Astrophysical Objects ◽

Alpha Effect ◽

The Stability ◽

The Magnetic Field

A wide range of astrophysical objects, such as the Sun, galaxies, stars, planets, accretion discs etc., have large-scale magnetic fields. Their generation is often based on the dynamo mechanism, which is connected with joint action of the alpha-effect and differential rotation. They compete with the turbulent diffusion. If the dynamo is intensive enough, the magnetic field grows, else it decays. The magnetic field evolution is described by Steenbeck—Krause—Raedler equations, which are quite difficult to be solved. So, for different objects, specific two-dimensional models are used. As for thin discs (this shape corresponds to galaxies and accretion discs), usually, no-z approximation is used. Some of the partial derivatives are changed by the algebraic expressions, and the solenoidality condition is taken into account as well. The field generation is restricted by the equipartition value and saturates if the field becomes comparable with it. From the point of view of mathematical physics, they can be characterized as stable points of the equations. The field can come to these values monotonously or have oscillations. It depends on the type of the stability of these points, whether it is a node or focus. Here, we study the stability of such points and give examples for astrophysical applications.

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Nuclear burning in collapsar accretion discs

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3002 ◽

2020 ◽

Vol 499 (3) ◽

pp. 4097-4113 ◽

Cited By ~ 1

Author(s):

Yossef Zenati ◽

Daniel M Siegel ◽

Brian D Metzger ◽

Hagai B Perets

Keyword(s):

Angular Momentum ◽

Gamma Ray ◽

Nuclear Reactions ◽

Reaction Network ◽

Accretion Discs ◽

Late Time ◽

Rotating Stars ◽

Stellar Envelope ◽

Nuclear Burning ◽

R Process

ABSTRACT The core collapse of massive, rapidly-rotating stars are thought to be the progenitors of long-duration gamma-ray bursts (GRB) and their associated hyperenergetic supernovae (SNe). At early times after the collapse, relatively low angular momentum material from the infalling stellar envelope will circularize into an accretion disc located just outside the black hole horizon, resulting in high accretion rates necessary to power a GRB jet. Temperatures in the disc mid-plane at these small radii are sufficiently high to dissociate nuclei, while outflows from the disc can be neutron-rich and may synthesize r-process nuclei. However, at later times, and for high progenitor angular momentum, the outer layers of the stellar envelope can circularize at larger radii ≳ 107 cm, where nuclear reactions can take place in the disc mid-plane (e.g. 4He + 16O → 20Ne + γ). Here we explore the effects of nuclear burning on collapsar accretion discs and their outflows by means of hydrodynamical α-viscosity torus simulations coupled to a 19-isotope nuclear reaction network, which are designed to mimic the late infall epochs in collapsar evolution when the viscous time of the torus has become comparable to the envelope fall-back time. Our results address several key questions, such as the conditions for quiescent burning and accretion versus detonation and the generation of 56Ni in disc outflows, which we show could contribute significantly to powering GRB SNe. Being located in the slowest, innermost layers of the ejecta, the latter could provide the radioactive heating source necessary to make the spectral signatures of r-process elements visible in late-time GRB-SNe spectra.

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