Hard and soft spectral states of ULXs
I discuss some differences between the observed spectral states of ultraluminous X-ray sources (ULXs) and the canonical scheme of spectral states defined in Galactic black holes. The standard interpretation of ULXs with a curved spectrum, or a moderately steep power-law with soft excess and high-ene...
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| Format: | Journal Article |
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Wiley - V C H Verlag GmbH & Co. KGaA
2011
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| Online Access: | http://hdl.handle.net/20.500.11937/39815 |
| _version_ | 1848755696285253632 |
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| author | Soria, Roberto |
| author_facet | Soria, Roberto |
| author_sort | Soria, Roberto |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | I discuss some differences between the observed spectral states of ultraluminous X-ray sources (ULXs) and the canonical scheme of spectral states defined in Galactic black holes. The standard interpretation of ULXs with a curved spectrum, or a moderately steep power-law with soft excess and high-energy downturn, is that they are an extension of the very high state, up to luminosities ≈1–3L Edd. Two competing models are Comptonization in a warm corona, and slim disk; I suggest bulk motion Comptonization in the radiatively-driven outflow as another possibility. The interpretation of ULXs with a hard power-law spectrum is more problematic. Some of them remain in that state over a large range of luminosities; others switch directly to a curved state without going through a canonical high/soft state. I suggest that those ULXs are in a high/hard state not seen in Galactic black holes; that state may overlap with the low/hard state at lower accretion rates, and extend all the way to Eddington accretion rates. If some black holes can reach Eddington accretion rates without switching to a standard-disk-dominated state, it is also possible that they never quench their steady jets. |
| first_indexed | 2025-11-14T09:00:24Z |
| format | Journal Article |
| id | curtin-20.500.11937-39815 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:00:24Z |
| publishDate | 2011 |
| publisher | Wiley - V C H Verlag GmbH & Co. KGaA |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-398152017-09-13T16:06:54Z Hard and soft spectral states of ULXs Soria, Roberto I discuss some differences between the observed spectral states of ultraluminous X-ray sources (ULXs) and the canonical scheme of spectral states defined in Galactic black holes. The standard interpretation of ULXs with a curved spectrum, or a moderately steep power-law with soft excess and high-energy downturn, is that they are an extension of the very high state, up to luminosities ≈1–3L Edd. Two competing models are Comptonization in a warm corona, and slim disk; I suggest bulk motion Comptonization in the radiatively-driven outflow as another possibility. The interpretation of ULXs with a hard power-law spectrum is more problematic. Some of them remain in that state over a large range of luminosities; others switch directly to a curved state without going through a canonical high/soft state. I suggest that those ULXs are in a high/hard state not seen in Galactic black holes; that state may overlap with the low/hard state at lower accretion rates, and extend all the way to Eddington accretion rates. If some black holes can reach Eddington accretion rates without switching to a standard-disk-dominated state, it is also possible that they never quench their steady jets. 2011 Journal Article http://hdl.handle.net/20.500.11937/39815 10.1002/asna.201011493 Wiley - V C H Verlag GmbH & Co. KGaA unknown |
| spellingShingle | Soria, Roberto Hard and soft spectral states of ULXs |
| title | Hard and soft spectral states of ULXs |
| title_full | Hard and soft spectral states of ULXs |
| title_fullStr | Hard and soft spectral states of ULXs |
| title_full_unstemmed | Hard and soft spectral states of ULXs |
| title_short | Hard and soft spectral states of ULXs |
| title_sort | hard and soft spectral states of ulxs |
| url | http://hdl.handle.net/20.500.11937/39815 |