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arXiv · 2502.09147

PSR J1231-1411 revisited: Pulse Profile Analysis of X-ray Observation

Liqiang Qi·Shijie Zheng·Juan Zhang·Mingyu Ge·Ang Li·Shuang-Nan Zhang·Fang-Jun Lu·Han-Long Peng·Liang Zhang·Hua Feng·Zhen Zhang·Yupeng Xu·Zheng-Wei Li·Li-Ming Song·Shu Zhang·Lian Tao·Wentao Ye
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Abstract

One of the primary goals of Neutron Star Interior Composition Explorer (NICER)-like X-ray missions is to impose stringent constraints on the neutron star equation of state by precisely measuring their masses and radii. NICER has recently expanded the dataset of inferred mass-radius relations for neutron stars, including four rotation-powered millisecond pulsars PSR J0030+0451, PSR J0740+6620, PSR J0437-4715, and PSR J1231-1411. In this work, the mass-radius relation and X-ray emitting region properties of PSR J1231-1411 are inferred with an independent pulse profile modeling based on the spherical star Schwarzschild-spacetime and Doppler approximation. With one single-temperature elongated hot spot and one single-temperature crescent hot spot, the inferred gravitational mass is $M = 1.12 \pm 0.07 M_{\odot}$ and the inferred equatorial radius is $R_{eq} = 9.91_{-0.86}^{+0.88}$ km (68% credible intervals). It provides an alternative geometry configuration of the X-ray emitting region for PSR J1231-1411 to sufficiently explain the observation data of NICER and XMM-Newton. The inferred radius is smaller than that derived by \citet{salmi2024nicer} ($M = 1.04_{-0.03}^{+0.05} M_{\odot}$, $R_{eq} = 12.6 \pm 0.3$ km), and the inferred mass is slightly higher in this work. The inferred geometry configurations of the X-ray emitting region in both works are non-antipodal, which is not consistent with a centered dipole magnetic field and suggests a complex magnetic field structure.

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Liqiang Qi, Shijie Zheng, Juan Zhang, Mingyu Ge, Ang Li, Shuang-Nan Zhang, Fang-Jun Lu, Han-Long Peng, Liang Zhang, Hua Feng, Zhen Zhang, Yupeng Xu, Zheng-Wei Li, Li-Ming Song, Shu Zhang, Lian Tao, Wentao Ye. 2025-02-13. PSR J1231-1411 revisited: Pulse Profile Analysis of X-ray Observation. https://doi.org/10.3847/1538-4357/adb42f

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