Probing burst-disc interaction and disc reflection in SAX J1808.4$-$3658 with NICER, XMM-Newton, and NuSTAR
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2026
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| _version_ | 1866917368759844864 |
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| author | Mandal, Manoj Naik, Sachindra Chhotaray, Birendra |
| author_facet | Mandal, Manoj Naik, Sachindra Chhotaray, Birendra |
| contents | We performed a comprehensive study of thermonuclear bursts from the millisecond X-ray pulsar SAX J1808.4$-$3658 with XMM-Newton and NICER. We report the results from the analysis of an intense burst with NICER using a self-consistent and physically motivated disc reflection modeling approach and investigate the burst-disc interaction. The dynamic evolution of the spectral parameters suggested evidence of photospheric radius expansion (PRE) of the neutron star using the disc reflection modeling approach, which indicates a maximum expansion of the photosphere up to 14.8$\pm$0.7 km. The corresponding blackbody temperature drops to a minimum of 1.9 keV. In addition, an emission line at 1 keV is observed, possibly originating from the Ne or Fe L-band transition as a result of the reprocessing of burst photons by cold gas in the accretion disc. The 1 keV emission line flux is found to be strongly correlated with the flux of the reflection component. We also investigated a thermonuclear burst observed with XMM-Newton EPIC-PN from SAX J1808.4$-$3658 using the variable persistent emission method and the disc reflection modeling approach. The X-ray reflection feature is also investigated in persistent emission using a NuSTAR observation. The best-fitting results provide an inner disc radius of $14_{-5.9}^{+9.7}$ $R_g$ and an inclination of $ 38^\circ-60^\circ$ during the NuSTAR observation. The magnetic field is estimated to be $\simeq$3.7 $\times$10$^8$ G at the poles of the neutron star. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_28189 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Probing burst-disc interaction and disc reflection in SAX J1808.4$-$3658 with NICER, XMM-Newton, and NuSTAR Mandal, Manoj Naik, Sachindra Chhotaray, Birendra High Energy Astrophysical Phenomena We performed a comprehensive study of thermonuclear bursts from the millisecond X-ray pulsar SAX J1808.4$-$3658 with XMM-Newton and NICER. We report the results from the analysis of an intense burst with NICER using a self-consistent and physically motivated disc reflection modeling approach and investigate the burst-disc interaction. The dynamic evolution of the spectral parameters suggested evidence of photospheric radius expansion (PRE) of the neutron star using the disc reflection modeling approach, which indicates a maximum expansion of the photosphere up to 14.8$\pm$0.7 km. The corresponding blackbody temperature drops to a minimum of 1.9 keV. In addition, an emission line at 1 keV is observed, possibly originating from the Ne or Fe L-band transition as a result of the reprocessing of burst photons by cold gas in the accretion disc. The 1 keV emission line flux is found to be strongly correlated with the flux of the reflection component. We also investigated a thermonuclear burst observed with XMM-Newton EPIC-PN from SAX J1808.4$-$3658 using the variable persistent emission method and the disc reflection modeling approach. The X-ray reflection feature is also investigated in persistent emission using a NuSTAR observation. The best-fitting results provide an inner disc radius of $14_{-5.9}^{+9.7}$ $R_g$ and an inclination of $ 38^\circ-60^\circ$ during the NuSTAR observation. The magnetic field is estimated to be $\simeq$3.7 $\times$10$^8$ G at the poles of the neutron star. |
| title | Probing burst-disc interaction and disc reflection in SAX J1808.4$-$3658 with NICER, XMM-Newton, and NuSTAR |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2603.28189 |