Discovery of two eclipsing X-ray binaries in M51
We discovered eclipses and dips in two luminous (and highly variable) X-ray sources in M 51. One (CXOM51 J132943.3+471135) is an ultraluminous supersoft source, with a thermal spectrum at a temperature of about 0.1 keV and characteristic blackbody radius of about 104 km. The other (CXOM51 J132946.1+...
| Main Authors: | , , , |
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| Format: | Journal Article |
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Oxford University Press
2018
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| Online Access: | http://hdl.handle.net/20.500.11937/69233 |
| _version_ | 1848762003275907072 |
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| author | Wang, S. Soria, Roberto Urquhart, Ryan Liu, J. |
| author_facet | Wang, S. Soria, Roberto Urquhart, Ryan Liu, J. |
| author_sort | Wang, S. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | We discovered eclipses and dips in two luminous (and highly variable) X-ray sources in M 51. One (CXOM51 J132943.3+471135) is an ultraluminous supersoft source, with a thermal spectrum at a temperature of about 0.1 keV and characteristic blackbody radius of about 104 km. The other (CXOM51 J132946.1+471042) has a two-component spectrum with additional thermal-plasma emission; it approached an X-ray luminosity of 1039 erg s−1 during outbursts in 2005 and 2012. From the timing of three eclipses in a series of Chandra observations, we determine the binary period (52.75 ± 0.63 h) and eclipse fraction (22±0.1 per cent ) of CXOM51 J132946.1+471042. We also identify a blue optical counterpart in archival Hubble Space Telescope images, consistent with a massive donor star (mass of ∼20–35 M⊙). By combining the X-ray light-curve parameters with the optical constraints on the donor star, we show that the mass ratio in the system must be M2 /M1 >~ 18 and therefore the compact object is most likely a neutron star (exceeding its Eddington limit in outburst). The general significance of our result is that we illustrate one method (applicable to high-inclination sources) of identifying luminous neutron star X-ray binaries, in the absence of X-ray pulsations or phase-resolved optical spectroscopy. Finally, we discuss the different X-ray spectral appearance expected from super-Eddington neutron stars and black holes at high viewing angles. |
| first_indexed | 2025-11-14T10:40:39Z |
| format | Journal Article |
| id | curtin-20.500.11937-69233 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T10:40:39Z |
| publishDate | 2018 |
| publisher | Oxford University Press |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-692332018-09-25T06:49:27Z Discovery of two eclipsing X-ray binaries in M51 Wang, S. Soria, Roberto Urquhart, Ryan Liu, J. We discovered eclipses and dips in two luminous (and highly variable) X-ray sources in M 51. One (CXOM51 J132943.3+471135) is an ultraluminous supersoft source, with a thermal spectrum at a temperature of about 0.1 keV and characteristic blackbody radius of about 104 km. The other (CXOM51 J132946.1+471042) has a two-component spectrum with additional thermal-plasma emission; it approached an X-ray luminosity of 1039 erg s−1 during outbursts in 2005 and 2012. From the timing of three eclipses in a series of Chandra observations, we determine the binary period (52.75 ± 0.63 h) and eclipse fraction (22±0.1 per cent ) of CXOM51 J132946.1+471042. We also identify a blue optical counterpart in archival Hubble Space Telescope images, consistent with a massive donor star (mass of ∼20–35 M⊙). By combining the X-ray light-curve parameters with the optical constraints on the donor star, we show that the mass ratio in the system must be M2 /M1 >~ 18 and therefore the compact object is most likely a neutron star (exceeding its Eddington limit in outburst). The general significance of our result is that we illustrate one method (applicable to high-inclination sources) of identifying luminous neutron star X-ray binaries, in the absence of X-ray pulsations or phase-resolved optical spectroscopy. Finally, we discuss the different X-ray spectral appearance expected from super-Eddington neutron stars and black holes at high viewing angles. 2018 Journal Article http://hdl.handle.net/20.500.11937/69233 10.1093/mnras/sty872 Oxford University Press fulltext |
| spellingShingle | Wang, S. Soria, Roberto Urquhart, Ryan Liu, J. Discovery of two eclipsing X-ray binaries in M51 |
| title | Discovery of two eclipsing X-ray binaries in M51 |
| title_full | Discovery of two eclipsing X-ray binaries in M51 |
| title_fullStr | Discovery of two eclipsing X-ray binaries in M51 |
| title_full_unstemmed | Discovery of two eclipsing X-ray binaries in M51 |
| title_short | Discovery of two eclipsing X-ray binaries in M51 |
| title_sort | discovery of two eclipsing x-ray binaries in m51 |
| url | http://hdl.handle.net/20.500.11937/69233 |