Birthplaces of X-ray emission lines in Cygnus X-3
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arXiv
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2025
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| author | Vilhu, Osmi Koljonen, Karri I. I. |
| author_facet | Vilhu, Osmi Koljonen, Karri I. I. |
| contents | We investigate the formation of X-ray emission lines in the wind of the Wolf-Rayet (WR) companion in Cyg X-3 by analyzing their orbital dynamics using Chandra High Energy Transmission Grating (HEG) observations during a hypersoft state. Our goal is to constrain the X-ray transparency of the recently discovered funnel-like structure surrounding the compact star, as revealed by X-ray polarimetry. All lines exhibit sinusoidal orbital modulation, with the velocity amplitude generally increasing and the orbital phase with the highest blueshift generally decreasing for ions with a higher ionisation potential. The {Fe}{xxvi}-line displays velocity extremes at phase 0.25 (blueshift) and 0.75 (redshift), indicating that the line-emitting region is close to the compact component (disc or corona) and thus reflects the orbital motion. The {Fe}{xxv}-line shows a complex behaviour that cannot be fully resolved with the Chandra/HEG resolution. Other lines display velocity extremes scattered around phase 0.5 (blueshift) and 0.0 (redshift), with velocity amplitudes of 100--300 km/s, suggesting their origin in the WR stellar wind between the two components along 3D ξ-surfaces. Parts of the emission lines of {Ar}{xviii} and {Ca}{xx} originated around the compact star (disc or corona). The recent polarisation funnel-modelling is consistent with the present results during the hypersoft state. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2506_19380 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Birthplaces of X-ray emission lines in Cygnus X-3 Vilhu, Osmi Koljonen, Karri I. I. High Energy Astrophysical Phenomena Solar and Stellar Astrophysics We investigate the formation of X-ray emission lines in the wind of the Wolf-Rayet (WR) companion in Cyg X-3 by analyzing their orbital dynamics using Chandra High Energy Transmission Grating (HEG) observations during a hypersoft state. Our goal is to constrain the X-ray transparency of the recently discovered funnel-like structure surrounding the compact star, as revealed by X-ray polarimetry. All lines exhibit sinusoidal orbital modulation, with the velocity amplitude generally increasing and the orbital phase with the highest blueshift generally decreasing for ions with a higher ionisation potential. The {Fe}{xxvi}-line displays velocity extremes at phase 0.25 (blueshift) and 0.75 (redshift), indicating that the line-emitting region is close to the compact component (disc or corona) and thus reflects the orbital motion. The {Fe}{xxv}-line shows a complex behaviour that cannot be fully resolved with the Chandra/HEG resolution. Other lines display velocity extremes scattered around phase 0.5 (blueshift) and 0.0 (redshift), with velocity amplitudes of 100--300 km/s, suggesting their origin in the WR stellar wind between the two components along 3D ξ-surfaces. Parts of the emission lines of {Ar}{xviii} and {Ca}{xx} originated around the compact star (disc or corona). The recent polarisation funnel-modelling is consistent with the present results during the hypersoft state. |
| title | Birthplaces of X-ray emission lines in Cygnus X-3 |
| topic | High Energy Astrophysical Phenomena Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2506.19380 |