Optical counterpart of HLX-1 during the 2010 outburst
We studied the optical counterpart of the intermediate-mass black hole candidate HLX-1 in ESO 243-49. We used a set of Very Large Telescope imaging observations from 2010 November, integrated by Swift X-ray data from the same epoch. We measured standard Vega brightnesses U= 23.89 ± 0.18 mag, B= 25.1...
| Main Authors: | , , , , |
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| Format: | Journal Article |
| Published: |
Wiley-Blackwell Publishing Ltd.
2012
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| Online Access: | http://hdl.handle.net/20.500.11937/3803 |
| _version_ | 1848744331496652800 |
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| author | Soria, Roberto Hakala, P. Hau, G. Gladstone, J. Kong, A. |
| author_facet | Soria, Roberto Hakala, P. Hau, G. Gladstone, J. Kong, A. |
| author_sort | Soria, Roberto |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | We studied the optical counterpart of the intermediate-mass black hole candidate HLX-1 in ESO 243-49. We used a set of Very Large Telescope imaging observations from 2010 November, integrated by Swift X-ray data from the same epoch. We measured standard Vega brightnesses U= 23.89 ± 0.18 mag, B= 25.19 ± 0.30 mag, V= 24.79 ± 0.34 mag and R= 24.71 ± 0.40 mag. Therefore, the source was ˜1 mag fainter in each band than in a set of Hubble Space Telescope images taken a couple of months earlier, when the X-ray flux was a factor of 2 higher. We conclude that during the 2010 September observations, the optical counterpart was dominated by emission from an irradiated disc (which responds to the varying X-ray luminosity), rather than by a star cluster around the black hole (which would not change). We modelled the Comptonized, irradiated X-ray spectrum of the disc, and found that the optical luminosity and colours in the 2010 November data are still consistent with emission from the irradiated disc, with a characteristic outer radius rout˜ 2800rin˜ 1013 cm and a reprocessing fraction ˜2 × 10-3. The optical colours are also consistent with a stellar population with age ?6 Myr (at solar metallicity) and mass ˜104 Msun; this is only an upper limit to the mass, if there is also a significant contribution from an irradiated disc. We strongly rule out the presence of a young superstar cluster, which would be too bright. An old globular cluster might be associated with HLX-1, as long as its mass ?2 × 106 Msun for an age of 10 Gyr, but it cannot significantly contribute to the observed very blue and variable optical/ultraviolet emission. |
| first_indexed | 2025-11-14T05:59:46Z |
| format | Journal Article |
| id | curtin-20.500.11937-3803 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T05:59:46Z |
| publishDate | 2012 |
| publisher | Wiley-Blackwell Publishing Ltd. |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-38032017-09-13T14:33:02Z Optical counterpart of HLX-1 during the 2010 outburst Soria, Roberto Hakala, P. Hau, G. Gladstone, J. Kong, A. We studied the optical counterpart of the intermediate-mass black hole candidate HLX-1 in ESO 243-49. We used a set of Very Large Telescope imaging observations from 2010 November, integrated by Swift X-ray data from the same epoch. We measured standard Vega brightnesses U= 23.89 ± 0.18 mag, B= 25.19 ± 0.30 mag, V= 24.79 ± 0.34 mag and R= 24.71 ± 0.40 mag. Therefore, the source was ˜1 mag fainter in each band than in a set of Hubble Space Telescope images taken a couple of months earlier, when the X-ray flux was a factor of 2 higher. We conclude that during the 2010 September observations, the optical counterpart was dominated by emission from an irradiated disc (which responds to the varying X-ray luminosity), rather than by a star cluster around the black hole (which would not change). We modelled the Comptonized, irradiated X-ray spectrum of the disc, and found that the optical luminosity and colours in the 2010 November data are still consistent with emission from the irradiated disc, with a characteristic outer radius rout˜ 2800rin˜ 1013 cm and a reprocessing fraction ˜2 × 10-3. The optical colours are also consistent with a stellar population with age ?6 Myr (at solar metallicity) and mass ˜104 Msun; this is only an upper limit to the mass, if there is also a significant contribution from an irradiated disc. We strongly rule out the presence of a young superstar cluster, which would be too bright. An old globular cluster might be associated with HLX-1, as long as its mass ?2 × 106 Msun for an age of 10 Gyr, but it cannot significantly contribute to the observed very blue and variable optical/ultraviolet emission. 2012 Journal Article http://hdl.handle.net/20.500.11937/3803 10.1111/j.1365-2966.2011.20281.x Wiley-Blackwell Publishing Ltd. fulltext |
| spellingShingle | Soria, Roberto Hakala, P. Hau, G. Gladstone, J. Kong, A. Optical counterpart of HLX-1 during the 2010 outburst |
| title | Optical counterpart of HLX-1 during the 2010 outburst |
| title_full | Optical counterpart of HLX-1 during the 2010 outburst |
| title_fullStr | Optical counterpart of HLX-1 during the 2010 outburst |
| title_full_unstemmed | Optical counterpart of HLX-1 during the 2010 outburst |
| title_short | Optical counterpart of HLX-1 during the 2010 outburst |
| title_sort | optical counterpart of hlx-1 during the 2010 outburst |
| url | http://hdl.handle.net/20.500.11937/3803 |