Spectra of black hole accretion models of ultraluminous X-ray sources
© 2017 The Authors. We present general relativistic radiation magnetohydrodynamics simulations of super- Eddington accretion on a 10M ☉ 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 fu...
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| Format: | Journal Article |
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Oxford University Press
2017
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| Online Access: | http://hdl.handle.net/20.500.11937/68572 |
| _version_ | 1848761836339462144 |
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| author | Narayan, R. Sadowski, A. Soria, Roberto |
| author_facet | Narayan, R. Sadowski, A. Soria, Roberto |
| author_sort | Narayan, R. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | © 2017 The Authors. We present general relativistic radiation magnetohydrodynamics simulations of super- Eddington accretion on a 10M ☉ 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 10 40 erg s -1 for pole-on observers. However, the angle-integrated radiative luminosities rarely exceed 2.5 × 10 39 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 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. |
| first_indexed | 2025-11-14T10:38:00Z |
| format | Journal Article |
| id | curtin-20.500.11937-68572 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T10:38:00Z |
| publishDate | 2017 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-685722018-09-25T06:16:33Z Spectra of black hole accretion models of ultraluminous X-ray sources Narayan, R. Sadowski, A. Soria, Roberto © 2017 The Authors. We present general relativistic radiation magnetohydrodynamics simulations of super- Eddington accretion on a 10M ☉ 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 10 40 erg s -1 for pole-on observers. However, the angle-integrated radiative luminosities rarely exceed 2.5 × 10 39 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 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. 2017 Journal Article http://hdl.handle.net/20.500.11937/68572 10.1093/mnras/stx1027 Oxford University Press fulltext |
| spellingShingle | Narayan, R. Sadowski, A. Soria, Roberto Spectra of black hole accretion models of ultraluminous X-ray sources |
| title | Spectra of black hole accretion models of ultraluminous X-ray sources |
| title_full | Spectra of black hole accretion models of ultraluminous X-ray sources |
| title_fullStr | Spectra of black hole accretion models of ultraluminous X-ray sources |
| title_full_unstemmed | Spectra of black hole accretion models of ultraluminous X-ray sources |
| title_short | Spectra of black hole accretion models of ultraluminous X-ray sources |
| title_sort | spectra of black hole accretion models of ultraluminous x-ray sources |
| url | http://hdl.handle.net/20.500.11937/68572 |