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| Main Authors: | , , , , , , |
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| Format: | Preprint |
| Published: |
2025
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| Subjects: | |
| Online Access: | https://arxiv.org/abs/2503.07987 |
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| _version_ | 1866910911543902208 |
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| author | Yu, Wenhui Li, Zhaosheng Pan, Yuanyue Yang, Xuejuan Chen, Yupeng Zhang, Shu Falanga, Maurizio |
| author_facet | Yu, Wenhui Li, Zhaosheng Pan, Yuanyue Yang, Xuejuan Chen, Yupeng Zhang, Shu Falanga, Maurizio |
| contents | We analyze the emission and absorption lines during photospheric radius expansion (PRE) X-ray bursts from the ultracompact binary 4U 1820--30, observed with the Neutron Star Interior Composition Explorer (NICER). Using Monte Carlo simulations to estimate the significance, we identified a 1 keV emission line from 14 bursts, a 3 keV absorption line from 12 bursts, and 1.6 keV absorption from one burst. By coadding the burst spectra at the maximum radius phase, we detected a 1.034 keV emission line with significance of $14.2σ$, and absorption lines at 1.64 and 3 keV with significances of $10.8σ$ and $11.7σ$, respectively. The observed energy shifts are consistent with the prediction from the burst-driven wind model, indicating that all three spectral features are produced by the PRE wind. Analysis of the ratios between the emission and absorption line energies suggests that the 1 keV feature is a superposition of several narrower Fe L-shell lines. To evaluate the scientific capabilities of the Hot Universe Baryon Surveyor (HUBS), we simulated mock observations of multiple narrow lines near 1 keV. The results demonstrate that HUBS is well suited for detailed studies of the 1 keV emission line during bursts, offering significant potential to advance our understanding of these phenomena. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_07987 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Emission and Absorption Lines in Photospheric Radius Expansion Bursts of 4U 1820$-$30 Yu, Wenhui Li, Zhaosheng Pan, Yuanyue Yang, Xuejuan Chen, Yupeng Zhang, Shu Falanga, Maurizio High Energy Astrophysical Phenomena We analyze the emission and absorption lines during photospheric radius expansion (PRE) X-ray bursts from the ultracompact binary 4U 1820--30, observed with the Neutron Star Interior Composition Explorer (NICER). Using Monte Carlo simulations to estimate the significance, we identified a 1 keV emission line from 14 bursts, a 3 keV absorption line from 12 bursts, and 1.6 keV absorption from one burst. By coadding the burst spectra at the maximum radius phase, we detected a 1.034 keV emission line with significance of $14.2σ$, and absorption lines at 1.64 and 3 keV with significances of $10.8σ$ and $11.7σ$, respectively. The observed energy shifts are consistent with the prediction from the burst-driven wind model, indicating that all three spectral features are produced by the PRE wind. Analysis of the ratios between the emission and absorption line energies suggests that the 1 keV feature is a superposition of several narrower Fe L-shell lines. To evaluate the scientific capabilities of the Hot Universe Baryon Surveyor (HUBS), we simulated mock observations of multiple narrow lines near 1 keV. The results demonstrate that HUBS is well suited for detailed studies of the 1 keV emission line during bursts, offering significant potential to advance our understanding of these phenomena. |
| title | Emission and Absorption Lines in Photospheric Radius Expansion Bursts of 4U 1820$-$30 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2503.07987 |