Revisiting the ultraluminous supersoft source in M 101: An optically thick outflow model
The M 101 galaxy contains the best-known example of an ultraluminous supersoft source (ULS), dominated by a thermal component at kT ≈ 0.1 keV. The origin of the thermal component and the relation between ULSs and standard (broad-band spectrum) ultraluminous X-ray sources are still controversial. We...
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| Format: | Journal Article |
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Oxford University Press
2016
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| Online Access: | http://hdl.handle.net/20.500.11937/44333 |
| _version_ | 1848756970416242688 |
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| author | Soria, Roberto Kong, A. |
| author_facet | Soria, Roberto Kong, A. |
| author_sort | Soria, Roberto |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | The M 101 galaxy contains the best-known example of an ultraluminous supersoft source (ULS), dominated by a thermal component at kT ≈ 0.1 keV. The origin of the thermal component and the relation between ULSs and standard (broad-band spectrum) ultraluminous X-ray sources are still controversial. We re-examined the X-ray spectral and timing properties of the M 101 ULS using archival Chandra and XMM–Newton observations. We show that the X-ray time-variability and spectral properties are inconsistent with standard-disc emission. The characteristic radius Rbb of the thermal emitter varies from epoch to epoch between ≈10 000 and ≈100 000 km; the colour temperature kTbb varies between ≈50 and ≈140 eV and the two quantities scale approximately as R bb ∝T −2 bb Rbb∝Tbb−2. In addition to the smooth continuum, we also find (at some epochs) spectral residuals well fitted with thermal-plasma models and absorption edges: we interpret this as evidence that we are looking at a clumpy, multitemperature outflow. We suggest that at sufficiently high accretion rates and inclination angles, the supercritical, radiatively driven outflow becomes effectively optically thick and completely thermalizes the harder X-ray photons from the inner part of the inflow, removing the hard spectral tail. We develop a simple, spherically symmetric outflow model and show that it is consistent with the observed temperatures, radii and luminosities. A larger, cooler photosphere shifts the emission peak into the far-UV and makes the source dimmer in X-rays but possibly ultraluminous in the UV. We compare our results and interpretation with those of Liu et al. |
| first_indexed | 2025-11-14T09:20:39Z |
| format | Journal Article |
| id | curtin-20.500.11937-44333 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:20:39Z |
| publishDate | 2016 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-443332017-09-13T14:29:23Z Revisiting the ultraluminous supersoft source in M 101: An optically thick outflow model Soria, Roberto Kong, A. The M 101 galaxy contains the best-known example of an ultraluminous supersoft source (ULS), dominated by a thermal component at kT ≈ 0.1 keV. The origin of the thermal component and the relation between ULSs and standard (broad-band spectrum) ultraluminous X-ray sources are still controversial. We re-examined the X-ray spectral and timing properties of the M 101 ULS using archival Chandra and XMM–Newton observations. We show that the X-ray time-variability and spectral properties are inconsistent with standard-disc emission. The characteristic radius Rbb of the thermal emitter varies from epoch to epoch between ≈10 000 and ≈100 000 km; the colour temperature kTbb varies between ≈50 and ≈140 eV and the two quantities scale approximately as R bb ∝T −2 bb Rbb∝Tbb−2. In addition to the smooth continuum, we also find (at some epochs) spectral residuals well fitted with thermal-plasma models and absorption edges: we interpret this as evidence that we are looking at a clumpy, multitemperature outflow. We suggest that at sufficiently high accretion rates and inclination angles, the supercritical, radiatively driven outflow becomes effectively optically thick and completely thermalizes the harder X-ray photons from the inner part of the inflow, removing the hard spectral tail. We develop a simple, spherically symmetric outflow model and show that it is consistent with the observed temperatures, radii and luminosities. A larger, cooler photosphere shifts the emission peak into the far-UV and makes the source dimmer in X-rays but possibly ultraluminous in the UV. We compare our results and interpretation with those of Liu et al. 2016 Journal Article http://hdl.handle.net/20.500.11937/44333 10.1093/mnras/stv2671 Oxford University Press fulltext |
| spellingShingle | Soria, Roberto Kong, A. Revisiting the ultraluminous supersoft source in M 101: An optically thick outflow model |
| title | Revisiting the ultraluminous supersoft source in M 101: An optically thick outflow model |
| title_full | Revisiting the ultraluminous supersoft source in M 101: An optically thick outflow model |
| title_fullStr | Revisiting the ultraluminous supersoft source in M 101: An optically thick outflow model |
| title_full_unstemmed | Revisiting the ultraluminous supersoft source in M 101: An optically thick outflow model |
| title_short | Revisiting the ultraluminous supersoft source in M 101: An optically thick outflow model |
| title_sort | revisiting the ultraluminous supersoft source in m 101: an optically thick outflow model |
| url | http://hdl.handle.net/20.500.11937/44333 |