Two-Dimensional Numerical Simulations of Supercritical Accretion Flows Revisited

Yang, Xiaohong; Yuan, Feng; Ohsuga, Ken; Bu, De-Fu

doi:10.1088/0004-637x/780/1/79

Cited by 44 publications

(73 citation statements)

References 56 publications

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“…Hence, the value of s for a disc with = 1 lies between 0 and 1/2. Since the power law index s for a case with α = 0.1 cannot be greater than 0.4 (Yang et al 2014), we assume that the value of s is in the range of 0.0 (a case without outflow) to 0.3 (a case with moderate outflow). In top left panel, the dimensionless thickness of disc H/r is illustrated.…”

Section: Resultsmentioning

confidence: 99%

“…Ohsuga et al 2005;Yuan et al 2012b;2012a;Bu et al 2013;Yang et al 2014;Bu & Gan 2018). Although recent theoretical studies showed that the power index can lie between 0.4 and 1.0 (Yuan, Wu, & Bu 2012a;Bu et al 2013;Yang et al 2014), the observations of Sgr A * combined with the radiatively inefficient accretion model have predicted a range of 0.3 < s < 0.4 (Yuan, Quataert, & Narayan 2003).…”

Section: Introductionmentioning

confidence: 99%

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Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field

Ghoreyshi

2020

Publ. Astron. Soc. Aust.

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The observations and simulations have revealed that large-scale magnetic field and outflows can exist in the inner regions of an advection-dominated accretion disc where the resistive diffusion may also be important. In the present paper, the roles of large-scale magnetic field and outflows in the structure of resistive advection-dominated accretion discs are explored by assuming that the accretion flow is radially self-similar. In the non-ideal magnetohydrodynamic (MHD) approximation, the results show that the angular velocity is always sub-Keplerian when both the outflow and the large-scale magnetic field are taken into account. A stronger toroidal field component leads to faster rotation, while the disc rotates with faster rate if the vertical field component is weaker. The increase of magnetic diffusivity causes the infall velocity to be close to Keplerian velocity. Although the previous studies in the ideal MHD approximation have shown that the disc temperature decreases due to the vertical field component, we find that the effect of vertical field component on the temperature of a resistive disc depends on the magnetic diffusivity. When the magnetic diffusivity is high, the more efficient mechanism for decreasing the disc temperature can be the outflows, and not the large-scale magnetic field. In such a limit of the magnetic diffusivity, the components of the large-scale magnetic field enhance the gas temperature. The increase of temperature can lead to heating and acceleration of the electrons and help us to explain the origin of phenomena such as the flares in Sgr A*. On the other hand, the infall velocity in such a limit rises as the temperature increases, and therefore the surface density falls to too low values. Any change in the density profile can alter the structure and the emitted spectrum of disc.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field

Ghoreyshi

2020

Publ. Astron. Soc. Aust.

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“…There is observational evidence of outflows from super-Eddington accretion disks (e.g., Gladstone et al 2009;Middleton et al 2011;Du et al 2015), which is also confirmed by numerical simulations (e.g., Yang et al 2014;Jiang et al 2014;. The theoretical works also suggest that outflows may be driven from the surface of a slim disk (McClintock et al 2006;Gu & Lu 2007;Jiao et al 2009;Gu 2012;Cao & Gu 2015).…”

Section: Introductionmentioning

confidence: 82%

A Global Solution to a Slim Accretion Disk with Radiation-driven Outflows

Feng

Cao

et al. 2019

ApJ

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The thickness of a slim disk is determined by the balance between the radiation force and the vertical component of the gravity of the black hole (BH). It was found that vertical gravity increases with the disk height, and it will decrease with the disk height if the disk thickness is above a critical value, which implies that gas at the disk surface may be driven into outflows by radiation force when the disk thickness surpasses the critical value. In this work, we derive a global solution to a slim disk with radiation-driven outflows. We find that the outflows are driven from the disk surface if the mass accretion rateṁ 1.78 − 1.91 (ṁ =Ṁ /Ṁ Edd , andṀ Edd = L Edd /0.1c 2 ) depending on BH mass, while the outflows are suppressed when the mass accretion rate is lower than this critical value. The mass accretion rate decreases with decreasing radius in the disk with outflows, and the rate of the gas swallowed by the BH is always limited toṁ in ∼ 1.78 − 1.91 even if the mass accretion rate at the outer edge of the disk is very high. This may set constraints on the massive BH growth through accretion in the early Universe. Due to the presence of outflows, there is an upper limit on the radiation flux of the disk, which leads to saturation of the continuum spectra of the disk with outflows at the high energy band. This may be tested by the observations of quasars or/and BH X-ray binaries.

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“…In previous studies (e.g., McKernan et al 2020b;Yang et al 2020b;Tagawa et al 2020aTagawa et al ,b, 2021Gilbaum & Stone 2021), an Eddington accretion rate or a Bondi accretion rate is usually assumed, which makes model predictions that are sensentive to the accretion rate highly uncertain. As shown in many analytic models (Blandford & Begelman 1999Begelman 2012) and numerical simulations (Yuan et al 2012a,b;Sadowski et al 2014;McKinney et al 2014;Yang et al 2014;Takahashi et al 2018), outflow naturally emerges in cases of supercritical accretion of compact objects, such that only a (small) fraction of inflowing gas at the outer boundary finally accretes onto the central compact object. In this paper, we aim to build a relativistic supercritical inflow-outflow model of BHs and apply this model to study the mass and spin evolution of sBHs embedded in AGN disks, along with EM emissions.…”

Section: Introductionmentioning

confidence: 95%

Supercritical accretion of stellar-mass compact objects in active galactic nuclei

Pan,

Yang

2021

Preprint

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Accretion disks of active galactic nuclei (AGN) have been proposed as promising sites for producing both (stellar-mass) compact object mergers and extreme mass ratio inspirals. Along with the disk-assisted migration/evolution process, ambient gas materials inevitably accrete onto the compact objects. The description of this process is subject to significant theoretical uncertainties in previous studies. It was commonly assumed that either an Eddington accretion rate or a Bondi accretion rate (or any rate in between) takes place, although these two rates can differ from each other by several orders of magnitude. As a result, the mass and spin evolution of compact objects within AGN disks are essentially unknown. In this work, we construct a relativistic supercritical inflow-outflow model for black hole (BH) accretion. We show that the radiation efficiency of the supercritical accretion of a stellar-mass BH (sBH) is generally too low to explain the proposed electromagnetic counterpart of GW190521. Applying this model to sBHs embedded in AGN disks, we find that, although the gas inflow rates at Bondi radii of these sBHs are in general highly super-Eddington, a large fraction of inflowing gas eventually escapes as outflows so that only a small fraction accretes onto the sBH, resulting in mildly super-Eddington BH absorption in most cases. We also implement this inflow-outflow model to study the evolution of neutron stars (NS) and white dwarfs (WD) in AGN disks, taking into account corrections from star sizes and star magnetic fields. It turns out to be difficult for WDs to grow to the Chandrasekhar limit via accretion because WDs are spun up more efficiently to reach the shedding limit before the Chandrasekhar limit. For NSs the accretion-induced collapse is possible if NS magnetic fields are sufficiently strong to guide the accretion flow outside the NS surface, keeping the NS in a slow rotation state during the whole accretion process.

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Two-Dimensional Numerical Simulations of Supercritical Accretion Flows Revisited

Cited by 44 publications

References 56 publications

Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field

Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field

A Global Solution to a Slim Accretion Disk with Radiation-driven Outflows

Supercritical accretion of stellar-mass compact objects in active galactic nuclei

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