Super-Eddington accretion discs around Kerr black holes

Beloborodov, Andrei M.

doi:10.1046/j.1365-8711.1998.01530.x

Cited by 110 publications

(116 citation statements)

References 15 publications

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“…For higher values of α their range of applicability is limited to lower luminosities (e.g., to 0.5L Edd for α = 0.1). Kerr-metric slim disks with low effective optical depth were discussed by Beloborodov (1998), who finds them to be significantly hotter than the optically thick ones. We have already started implementing a radiative transfer scheme valid for disks with small effective optical depths into the scheme introduced in this work.…”

Section: Discussionmentioning

confidence: 99%

Relativistic slim disks with vertical structure

Sądowski

Abramowicz

Bursa

et al. 2011

A&A

137

149

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We report on a scheme for incorporating vertical radiative energy transport into a fully relativistic, Kerr-metric model of optically thick, advective, transonic alpha disks. Our code couples the radial and vertical equations of the accretion disk. The flux was computed in the diffusion approximation, and convection is included in the mixing-length approximation. We present the detailed structure of this "two-dimensional" slim-disk model for α = 0.01. We then calculated the emergent spectra integrated over the disk surface. The values of surface density, radial velocity, and the photospheric height for these models differ by 20%-30% from those obtained in the polytropic, height-averaged slim disk model considered previously. However, the emission profiles and the resulting spectra are quite similar for both types of models. The effective optical depth of the slim disk becomes lower than unity for high values of the alpha parameter and for high accretion rates.

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Section: Discussionmentioning

confidence: 99%

Relativistic slim disks with vertical structure

Sądowski

Abramowicz

Bursa

et al. 2011

A&A

137

149

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“…1. (i) In the innermost regions (R < R ph,in ), the wind is essentially transparent (τ ≤ 1) and so the emission will appear as a distorted 'hot disc', peaking at a characteristic temperature, T in (modified by some colour temperature correction, spin and overheating; see Beloborodov 1998;Suleimanov et al 2002;Kawaguchi 2003).…”

Section: T H E S U P E R C R I T I C a L M O D E L O F Ac C R E T I O Nmentioning

confidence: 99%

“…Schematic representation of the supercritical model for bright (>3 × 10 39 erg s −1 ) ULXs (P07) where an optically thick wind is launched from the surface of a large scaleheight flow. This flow is driven from the disc from R sph (≈ṁ 0 R in ; Shakura & Sunyaev 1973) down to R ph,in within which the outflow is effectively transparent and the underlying disc emission can emerge (which may be further distorted by advection, spin and overheating; P07, Beloborodov 1998;Suleimanov et al 2002;Kawaguchi 2003). Variability due to obscuration/scattering can be introduced when the wind is inhomogeneous -expected on large scales via radial propagation of flux (Lyubarskii 1997) and seen on small scales in 2D MHD simulations (Takeuchi et al 2013(Takeuchi et al , 2014.…”

Section: T H E S U P E R C R I T I C a L M O D E L O F Ac C R E T I O Nmentioning

confidence: 99%

A spectral-timing model for ULXs in the supercritical regime

Middleton¹,

Heil

Pintore

et al. 2015

Monthly Notices of the Royal Astronomical Society

188

298

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Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. ABSTRACTUltraluminous X-ray sources (ULXs) with luminosities lying between ∼3 × 10 39 and 2 × 10 40 erg s −1 represent a contentious sample of objects as their brightness, together with a lack of unambiguous mass estimates for the vast majority of the central objects, leads to a degenerate scenario where the accretor could be a stellar remnant (black hole or neutron star) or intermediate-mass black hole (IMBH). Recent, high-quality observations imply that the presence of IMBHs in the majority of these objects is unlikely unless the accretion flow somehow deviates strongly from expectation based on objects with known masses. On the other hand, physically motivated models for supercritical inflows can re-create the observed X-ray spectra and their evolution, although have been lacking a robust explanation for their variability properties. In this paper, we include the effect of a partially inhomogeneous wind that imprints variability on to the X-ray emission via two distinct methods. The model is heavily dependent on both inclination to the line of sight and mass accretion rate, resulting in a series of qualitative and semiquantitative predictions. We study the time-averaged spectra and variability of a sample of well-observed ULXs, finding that the source behaviours can be explained by our model in both individual cases as well as across the entire sample, specifically in the trend of hardness-variability power. We present the covariance spectra for these sources for the first time, which shed light on the correlated variability and issues associated with modelling broad ULX spectra.Key words: accretion, accretion discs -X-rays: binaries. I N T RO D U C T I O NUltraluminous X-ray sources (ULXs) have been widely observed in the local Universe, with inferred isotropic luminosities above 10 39 erg s −1 (Roberts 2007;Feng & Soria 2011). Those below ∼3 × 10 39 erg s −1 can be readily associated with accretion on to stellar mass black holes (BHs) (∼10 M ) accreting close to or at their Eddington limit (see Sutton, Roberts & Middleton 2013, and references therein). There is now strong evidence to support this assertion, with the discovery of extremely bright ballistic jets from a ULX in M31 Middleton, Miller-Jones & Fender 2014b), which unambiguously links the flow with Eddington rate accretion (Fender, Belloni & Gallo 2004), and the first dynamical mass measurement of the compact object in a ULX, from M101 E-mail: mjm@ast.cam.ac.uk ULX-1 (Liu et al. 2013). Ob...

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“…However, whether the Eddington limit should be applied or not needs to be further investigated, since the luminosity generated by accretion in excess of this limit might be carried away from the system via a strong wind, or transfered to a disc. SuperEddington accretion rates may be important for the formation of low-mass X-ray binaries and millisecond pulsars (Webbink & Kalogera 1997) and also for modeling X-ray emission from quasars due to accretion from a disc onto a fast rotating black hole (Beloborodov 1998). Imposing the limit diminishes the birth rate of type Ia supernovae (Livio 2000).…”

Section: Mass Transfer In Compact Binariesmentioning

confidence: 99%

The gravitational wave signal from diverse populations of double white dwarf binaries in the Galaxy

Jeffery

2010

A&A

130

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Context. The gravitational wave (GW) background in the range 0.01−30 mHz has been assumed to be dominated by unresolved radiation from double white dwarf binaries (DWDs). Recent investigations indicate that, at short periods, a number of DWDs should be resolvable sources of GW. Aims. We characterize the GW signal which would be detected by LISA from DWDs in the Galaxy. Methods. We have constructed a Galactic model in which we consider distinct contributions from the bulge, thin disc, thick disc, and halo, and subsequently executed a population synthesis approach to determine the birth rates, numbers, and period distributions of DWDs within each component. Results. In the Galaxy as a whole, our model predicts the current birth rate of DWDs to be 3.21 × 10 −2 yr −1 , the local density to be 2.2 × 10 −4 pc −3 and the total number to be 2.76 × 10 8 . Assuming SNIa are formed from the merger of two CO white dwarfs, the SNIa rate should be 0.0013 yr −1 . The frequency spectra of DWD strain amplitude and number distribution are presented as a function of galactic component, DWD type, formation channel, and metallicity. Conclusions. We confirm that CO+He and He+He white dwarf (WD) pairs should dominate the GW signal at very high frequencies (log f Hz −1 > −2.3), while CO+CO and ONeMg WD pairs have a dominant contribution at log f Hz −1 ≤ −2.3. Formation channels involving two common-envelope (CE) phases or a stable Roche lobe overflow phase followed by a CE phase dominate the production of DWDs detectable by LISA at log f Hz −1 > −4.5. DWDs with the shortest orbital periods will come from the CE+CE channel. The Exposed Core plus CE channel is a minor channel. A number of resolved DWDs would be detected, making up 0.012% of the total number of DWDs in the Galaxy. The majority of these would be CO+He and He+He pairs formed through the CE+CE channel.

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Super-Eddington accretion discs around Kerr black holes

Cited by 110 publications

References 15 publications

Relativistic slim disks with vertical structure

Relativistic slim disks with vertical structure

A spectral-timing model for ULXs in the supercritical regime

The gravitational wave signal from diverse populations of double white dwarf binaries in the Galaxy

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