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arXiv 1909.07977astro-ph.HE
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多历元X射线爆发模拟:具有1D模拟大网格的MCMC

Multi-epoch X-ray burst modelling: MCMC with large grids of 1D simulations

Zac Johnston, Alexander Heger, Duncan K. Galloway

摘要:

I型X射线爆发是在吸积的中子星表面反复发生的热核爆炸。将观测到的爆发与计算模型相匹配有助于限制系统特性,例如中子星的质量和半径、地壳加热速率和吸积燃料成分,但迄今为止系统的参数研究有限。我们首次将马尔可夫链蒙特卡罗方法应用于一维突发模型,通过同时拟合多个观测历元,获得了“时钟突发”GS 1826 $-$ 238的系统参数估计。我们探讨了经常保持不变的多个参数,包括中子星质量,地壳加热速率和氢成分。为了提高计算效率,我们预先计算了3840个KEPLER模型的网格-迄今为止最大的一维爆发模拟集-通过在模型网格上插值,我们可以快速采样爆发预测。我们得到的CNO金属丰度的$Z_\mathrm{CNO} = 0.010^{+0.005}_{-0.004}$,氢分数的$X_0 = 0.74^{+0.02}_{-0.03}$,距离$d \sqrt{ξ_\mathrm{b}} = 6.5^{+0.4}_{-0.6}\, \mathrm{kpc}$,和系统的倾斜度$i = {69^{+2}_{-3}}^{\circ}$的估计。

英文摘要:

Type-I X-ray bursts are recurring thermonuclear explosions on the surface of accreting neutron stars. Matching observed bursts to computational models can help to constrain system properties, such as the neutron star mass and radius, crustal heating rates, and the accreted fuel composition, but systematic parameter studies to date have been limited. We apply Markov chain Monte Carlo methods to 1D burst models for the first time, and obtain system parameter estimations for the `Clocked Burster', GS 1826$-$238, by fitting multiple observed epochs simultaneously. We explore multiple parameters which are often held constant, including the neutron star mass, crustal heating rate, and hydrogen composition. To improve the computational efficiency, we precompute a grid of 3840 KEPLER models - the largest set of 1D burst simulations to date - and by interpolating over the model grid, we can rapidly sample burst predictions. We obtain estimates for a CNO metallicity of $Z_\mathrm{CNO} = 0.010^{+0.005}_{-0.004}$, a hydrogen fraction of $X_0 = 0.74^{+0.02}_{-0.03}$, a distance of $d \sqrt{ξ_\mathrm{b}} = 6.5^{+0.4}_{-0.6}\, \mathrm{kpc}$, and a system inclination of $i = {69^{+2}_{-3}}^{\circ}$.

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