Numerical $\texttt{AXP4}$ Simulations of Pulse Profiles for Binary Accreting X-ray Pulsars $-$ II: A Case Study of Centaurus X-3
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arXiv
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| Natura: | Preprint |
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2024
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| _version_ | 1866916357136711680 |
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| author | Shirke, Parisee S. Dewangan, Gulab C. |
| author_facet | Shirke, Parisee S. Dewangan, Gulab C. |
| contents | The pulse shapes simulated in the accompanying paper Part $-$ I are compared with observations of a model binary accreting X-ray pulsar, Centaurus X-3. With known Cen X-3 inclination angles provided as input to the $\texttt{AXP4}$ code, the generated pulse profile is suitably compared with the corresponding observed energy-resolved $\textit{AstroSat}$/LAXPC pulse profile. The pulsed fraction is proposed as a robust, quantitative measure for estimating the size of the emission region of Centaurus X-3 by extending the simulations to include spherical caps of varying fractional surface coverage of the neutron star $-$ over the full range of $0-100\%$, up to very large caps (with polar half angle $> 30^{\circ}$). The hotspot radius thus derived drops by an order of magnitude from $12.27$ km to $1.36^{+0.29}_{-0.26}$ km, within the ballpark of the standard model value of $\sim$$1$ km, after including the effect of gravitational light bending, lending further weight to its routine emphasis in the literature. The energy- and luminosity-dependence of the composite gravitationally bent and slab-integrated pulse profiles is further studied. As the pulse profile is sensitive to luminosity variations, the correlation of the size of a finite polar cap and its dependence on X-ray luminosity $-$ through the rate and subsequently, the geometry of accretion $-$ is discussed. Although a single, model pulsar was chosen for this work to exhibit the depth of the physical and astrophysical prospects of such a probe, this exercise can be extended to a wide range of existing X-ray pulse profiles of known binary accreting pulsars available in galactic catalogs, especially, with the possible inclusion of accretion columns (with cylindrical co-ordinate transformation) in the future. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2408_07504 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Numerical $\texttt{AXP4}$ Simulations of Pulse Profiles for Binary Accreting X-ray Pulsars $-$ II: A Case Study of Centaurus X-3 Shirke, Parisee S. Dewangan, Gulab C. High Energy Astrophysical Phenomena The pulse shapes simulated in the accompanying paper Part $-$ I are compared with observations of a model binary accreting X-ray pulsar, Centaurus X-3. With known Cen X-3 inclination angles provided as input to the $\texttt{AXP4}$ code, the generated pulse profile is suitably compared with the corresponding observed energy-resolved $\textit{AstroSat}$/LAXPC pulse profile. The pulsed fraction is proposed as a robust, quantitative measure for estimating the size of the emission region of Centaurus X-3 by extending the simulations to include spherical caps of varying fractional surface coverage of the neutron star $-$ over the full range of $0-100\%$, up to very large caps (with polar half angle $> 30^{\circ}$). The hotspot radius thus derived drops by an order of magnitude from $12.27$ km to $1.36^{+0.29}_{-0.26}$ km, within the ballpark of the standard model value of $\sim$$1$ km, after including the effect of gravitational light bending, lending further weight to its routine emphasis in the literature. The energy- and luminosity-dependence of the composite gravitationally bent and slab-integrated pulse profiles is further studied. As the pulse profile is sensitive to luminosity variations, the correlation of the size of a finite polar cap and its dependence on X-ray luminosity $-$ through the rate and subsequently, the geometry of accretion $-$ is discussed. Although a single, model pulsar was chosen for this work to exhibit the depth of the physical and astrophysical prospects of such a probe, this exercise can be extended to a wide range of existing X-ray pulse profiles of known binary accreting pulsars available in galactic catalogs, especially, with the possible inclusion of accretion columns (with cylindrical co-ordinate transformation) in the future. |
| title | Numerical $\texttt{AXP4}$ Simulations of Pulse Profiles for Binary Accreting X-ray Pulsars $-$ II: A Case Study of Centaurus X-3 |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2408.07504 |