SIMBAD references

2017MNRAS.469.2997N - Mon. Not. R. Astron. Soc., 469, 2997-3014 (2017/August-2)

Spectra of black hole accretion models of ultraluminous X-ray sources.


Abstract (from CDS):

We present general relativistic radiation magnetohydrodynamics simulations of super-Eddington accretion on a 10 M black hole. We consider a range of mass accretion rates, black hole spins and magnetic field configurations. We compute the spectra and images of the models as a function of viewing angle and compare them with the observed properties of ultraluminous X-ray sources (ULXs). The models easily produce apparent luminosities in excess of 1040 erg s–1 for pole-on observers. However, the angle-integrated radiative luminosities rarely exceed 2.5 x 1039 erg s–1 even for mass accretion rates of tens of Eddington. The systems are thus radiatively inefficient, though they are energetically efficient when the energy output in winds and jets is also counted. The simulated models reproduce the main empirical types of spectra - disc-like, supersoft, soft, hard - observed in ultraluminous X-ray sources (ULXs). The magnetic field configuration, whether 'standard and normal evolution' (SANE) or 'magnetically arrested disc' (MAD), has a strong effect on the results. In SANE models, the X-ray spectral hardness is almost independent of accretion rate, but decreases steeply with increasing inclination. MAD models with non-spinning black holes produce significantly softer spectra at higher values of {dot}M, even at low inclinations. MAD models with rapidly spinning black holes are unique. They are radiatively efficient (efficiency factor ∼10-20 per cent), superefficient when the mechanical energy output is also included (70 per cent) and produce hard blazar-like spectra. In all models, the emission shows strong geometrical beaming, which disagrees with the more isotropic illumination favoured by observations of ULX bubbles.

Abstract Copyright: © 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society

Journal keyword(s): accretion, accretion discs - black hole physics - radiative transfer - methods: numerical - X-rays: binaries - X-rays: binaries

Simbad objects: 9

goto Full paper

goto View the reference in ADS

To bookmark this query, right click on this link: simbad:2017MNRAS.469.2997N and select 'bookmark this link' or equivalent in the popup menu


© Université de Strasbourg/CNRS

    • Contact