The nature of the companion star in Circinus X-1
© 2015 The Authors. We present optical spectra and images of the X-ray binary Circinus X-1. The optical light curve of Cir X-1 is strongly variable, changing in brightness by 1.2 mag in the space of four days. The shape of the light curve is consistent with that seen in the 1980s, when the X-ray and...
| Main Authors: | , , |
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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/20.500.11937/45808 |
| _version_ | 1848757387958157312 |
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| author | Johnston, H. Soria, Roberto Gibson, J. |
| author_facet | Johnston, H. Soria, Roberto Gibson, J. |
| author_sort | Johnston, H. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | © 2015 The Authors. We present optical spectra and images of the X-ray binary Circinus X-1. The optical light curve of Cir X-1 is strongly variable, changing in brightness by 1.2 mag in the space of four days. The shape of the light curve is consistent with that seen in the 1980s, when the X-ray and radio counterparts of the source were at least ten times as bright as they are currently. We detect strong, variable H a emission lines, consisting of multiple components which vary with orbital phase. We estimate the extinction to the source from the strength of the diffuse interstellar bands and the Balmer decrement; the two methods give AV = 7.6 ± 0.6mag and AV > 9.1 mag, respectively. The optical light curve can be modelled as arising from irradiation of the companion star by the central X-ray source, where a low-temperature star fills its Roche lobe in an orbit of moderate eccentricity (e ~ 0.4). We suggest that the companion star is overluminous and underdense, due to the impact of the supernova which occurred less than 5000 yr ago. |
| first_indexed | 2025-11-14T09:27:18Z |
| format | Journal Article |
| id | curtin-20.500.11937-45808 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T09:27:18Z |
| publishDate | 2016 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-458082017-09-13T14:24:47Z The nature of the companion star in Circinus X-1 Johnston, H. Soria, Roberto Gibson, J. © 2015 The Authors. We present optical spectra and images of the X-ray binary Circinus X-1. The optical light curve of Cir X-1 is strongly variable, changing in brightness by 1.2 mag in the space of four days. The shape of the light curve is consistent with that seen in the 1980s, when the X-ray and radio counterparts of the source were at least ten times as bright as they are currently. We detect strong, variable H a emission lines, consisting of multiple components which vary with orbital phase. We estimate the extinction to the source from the strength of the diffuse interstellar bands and the Balmer decrement; the two methods give AV = 7.6 ± 0.6mag and AV > 9.1 mag, respectively. The optical light curve can be modelled as arising from irradiation of the companion star by the central X-ray source, where a low-temperature star fills its Roche lobe in an orbit of moderate eccentricity (e ~ 0.4). We suggest that the companion star is overluminous and underdense, due to the impact of the supernova which occurred less than 5000 yr ago. 2016 Journal Article http://hdl.handle.net/20.500.11937/45808 10.1093/mnras/stv2669 Oxford University Press fulltext |
| spellingShingle | Johnston, H. Soria, Roberto Gibson, J. The nature of the companion star in Circinus X-1 |
| title | The nature of the companion star in Circinus X-1 |
| title_full | The nature of the companion star in Circinus X-1 |
| title_fullStr | The nature of the companion star in Circinus X-1 |
| title_full_unstemmed | The nature of the companion star in Circinus X-1 |
| title_short | The nature of the companion star in Circinus X-1 |
| title_sort | nature of the companion star in circinus x-1 |
| url | http://hdl.handle.net/20.500.11937/45808 |