Relativistic X-ray reflection from the accreting millisecond X-ray pulsar IGR J17498-2921
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arXiv
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| Natura: | Preprint |
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2024
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| author | Bhattacharya, Mahasweta Mondal, Aditya S. Pahari, Mayukh Raychaudhuri, Biplab Ghosh, Rohit Dewangan, Gulab C. |
| author_facet | Bhattacharya, Mahasweta Mondal, Aditya S. Pahari, Mayukh Raychaudhuri, Biplab Ghosh, Rohit Dewangan, Gulab C. |
| contents | The accreting millisecond X-ray pulsar IGR J17498-2921 went into X-ray outburst on April 13-15, 2023, for the first time since its discovery on August 11, 2011. Here, we report on the first follow-up \nustar{} observation of the source, performed on April 23, 2023, around ten days after the peak of the outburst. The \nustar{} spectrum of the persistent emission ($3-60$ \kev{} band) is well described by an absorbed blackbody with a temperature of $kT_{bb}=1.61\pm 0.04$\kev{}, most likely arising from the NS surface and a Comptonization component with power-law index $Γ=1.79\pm0.02$, arising from a hot corona at $kT_{e}=16\pm 2$ keV. The X-ray spectrum of the source shows robust reflection features which have not been observed before. We use a couple of self-consistent reflection models, {\tt relxill} and {\tt relxillCp}, to fit the reflection features. We find an upper limit to the inner disc radius of $ 6\: R_{ISCO}$ and $ 9\: R_{ISCO}$ from {\tt relxill} and {\tt relxillCp} model, respectively. The inclination of the system is estimated to be $\simeq 40\degr$ from both reflection models. Assuming magnetic truncation of the accretion disc, the upper limit of magnetic field strength at the pole of the NS is found to be $B\lesssim 1.8\times 10^{8}$ G. Furthermore, the \nustar{} observation revealed two type I X-ray bursts and the burst spectroscopy confirms the thermonuclear nature of the burst. The blackbody temperature reaches nearly $2.2$ keV at the peak of the burst. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2408_06193 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Relativistic X-ray reflection from the accreting millisecond X-ray pulsar IGR J17498-2921 Bhattacharya, Mahasweta Mondal, Aditya S. Pahari, Mayukh Raychaudhuri, Biplab Ghosh, Rohit Dewangan, Gulab C. High Energy Astrophysical Phenomena The accreting millisecond X-ray pulsar IGR J17498-2921 went into X-ray outburst on April 13-15, 2023, for the first time since its discovery on August 11, 2011. Here, we report on the first follow-up \nustar{} observation of the source, performed on April 23, 2023, around ten days after the peak of the outburst. The \nustar{} spectrum of the persistent emission ($3-60$ \kev{} band) is well described by an absorbed blackbody with a temperature of $kT_{bb}=1.61\pm 0.04$\kev{}, most likely arising from the NS surface and a Comptonization component with power-law index $Γ=1.79\pm0.02$, arising from a hot corona at $kT_{e}=16\pm 2$ keV. The X-ray spectrum of the source shows robust reflection features which have not been observed before. We use a couple of self-consistent reflection models, {\tt relxill} and {\tt relxillCp}, to fit the reflection features. We find an upper limit to the inner disc radius of $ 6\: R_{ISCO}$ and $ 9\: R_{ISCO}$ from {\tt relxill} and {\tt relxillCp} model, respectively. The inclination of the system is estimated to be $\simeq 40\degr$ from both reflection models. Assuming magnetic truncation of the accretion disc, the upper limit of magnetic field strength at the pole of the NS is found to be $B\lesssim 1.8\times 10^{8}$ G. Furthermore, the \nustar{} observation revealed two type I X-ray bursts and the burst spectroscopy confirms the thermonuclear nature of the burst. The blackbody temperature reaches nearly $2.2$ keV at the peak of the burst. |
| title | Relativistic X-ray reflection from the accreting millisecond X-ray pulsar IGR J17498-2921 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2408.06193 |