利用热核暴集束约束中子星性质：应用于SRGA J144459.2-604207
Constraining neutron-star properties with ensembles of thermonuclear bursts: application to SRGA J144459.2-604207
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中文总结 AI 辅助
本文开发BEANSP软件包的“集束”分析模式，将其应用于SRGA J144459.2-604207，约束其系统性质，发现其氢丰度超限制，距离可能为6-11千秒差距。
中文摘要 AI 辅助
从热核（I型）X射线暴推导其宿主中子星的性质仍是一项挑战，原因在于数据不完整、参数空间为多维，且缺乏合适的模型与分析工具。本文介绍BEANSP软件包的进一步开发，新增“集束”分析模式，该模式利用部分天体展现的一致且规则的“周期性”暴发现象；此模式每周期仅需一次模型评估，因此比之前的“训练”模式高效得多。我们将该代码应用于最知名的展现“周期性”爆发的天体GS 1826-24，利用为此预先计算的KEPLER模型网格，发现与先前研究吻合良好。我们对模拟数据开展实验，以合理精度恢复了与暴发起爆相关的输入参数，但对系统距离、发射各向异性及中子星质量和半径的恢复精度较低。最后，我们收集了14个每日爆发周期，覆盖吸积驱动毫秒脉冲星SRGA J144459.2-604207的2024年爆发，并通过与SETTLE模型预测对比尝试约束该天体的系统性质。我们发现，对于略低于太阳丰度的燃料成分，氢丰度X≈0.54、CNO金属丰度Z_CNO≈0.01，观测结果与模型预测吻合良好；然而，我们注意到推导的氢丰度超出了单独确定的0.4的限制，且采用的模型可能无法为该暴发起爆机制提供足够准确的预测。推导的距离取决于对系统倾角及对应持续发射各向异性的假设，可能处于6-11千秒差距范围内。未来采用更具物理真实性的模型应用于该天体及其他富氢爆发天体，是一条有前景的途径。
英文摘要
Deducing the properties of the host neutron stars from thermonuclear (type-I) X-ray bursts remains a challenge, due to incomplete data, multidimensional parameter space, and dearth of suitable models and analysis tools. Here we describe further development of the BEANSP package, with a new "ensemble" analysis mode utilising the consistent and regular "clocked" bursting exhibited by some sources. This mode requires only one model evaluation per epoch, and so is much more efficient than the previous "train" mode. We apply the code to the best-known source exhibiting "clocked" bursting, GS 1826-24, utilising a grid of KEPLER models pre-calculated for this purpose, and find good agreement with a previous study. We performed experiments on simulated data, and recovered input parameters related to the burst ignition with reasonable accuracy, but less so for the system distance, emission anisotropy and neutron star mass and radius. Finally, we assembled a set of 14 daily burst epochs covering the 2024 outburst of the accretion-powered millisecond pulsar SRGA J144459.2-604207, and attempted to constrain the system properties of this object by comparing to SETTLE model predictions. We find reasonably good agreement between the observations and model predictions for a mildly sub-solar fuel composition, with H-fraction $X\approx0.54$ and CNO metallicity $Z_{\rm CNO}\approx0.01$. However, we note that the inferred H-fraction is in excess of the limit of 0.4 established separately, and the adopted model may not provide sufficiently accurate predictions for this burst ignition regime. The inferred distance depends on assumptions about the system inclination and corresponding anisotropy of the persistent emission, and is likely in the range 6-11 kpc. Future applications with more physically realistic models are a promising avenue for this and other sources with H-rich bursts.
