Gaia 中子星：星族统计、诞生率及其与其他中子星群体的联系
Gaia neutron stars: demographics, birth rates, and connections to other neutron star populations
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中文总结 AI 辅助
本研究通过建模 Gaia 选择函数并运用分层贝叶斯推断，揭示了 Gaia 中子星的内在星族特征（周期、质量、偏心率分布），并估算其空间密度与诞生率，发现其诞生率远低于高质量 X 射线双星，为理解其形成机制提供了关键约束。
中文摘要 AI 辅助
Gaia DR3 揭示了一类新的中子星（NS），它们处于天文单位（au）尺度的轨道上，并与太阳型伴星相伴。这些“Gaia 中子星”如何形成仍不清楚，而约束其内在星族属性是理解其起源的必要步骤。然而，目前由 27 个 Gaia 中子星候选体组成的样本受到 Gaia 天体测量灵敏度的强烈偏差影响。在本工作中，我们仔细建模了 Gaia 的选择函数，并将其纳入分层贝叶斯框架中，以推断 Gaia 中子星星族的内在（intrinsic）统计特征。我们发现，该星族倾向于周期分布呈幂律下降，幂律斜率为 $\alpha_P=-0.75 \pm 0.35$；可见恒星质量分布峰值位于 $M_1\approx 0.85~{\rm M_\odot}$ 附近（$\sigma_{M_1} \approx 0.2~{\rm M_\odot}$）；中子星质量分布峰值位于 $M_{\rm NS}\approx 1.3~{\rm M_\odot}$ 附近，并带有向高质量端的拖尾；偏心率分布则偏向中等至较大的偏心率。内在空间密度为 $n\approx120~{\rm kpc^{-3}}$（在 2 kpc 范围内），这意味着目前仅发现了本地 Gaia 中子星星族的约 $\sim3\\%$。我们的预测表明，Gaia DR4 将把样本增加到约 $\sim300$–650 个中子星候选体，包括能够触及更长轨道周期的样本，这将为形成模型提供直接检验。最后，我们将 Gaia 中子星置于更广泛的银河系中子星星族背景下，通过比较其内在诞生率、寿命和规模与其他孤立及双星中子星类别，发现仅有 0.01%–1% 的中子星诞生于具有太阳型伴星的 au 尺度轨道上，这使得 Gaia 中子星的诞生率比高质量 X 射线双星低 10–100 倍，但与共生 X 射线双星的诞生率大致相当。
英文摘要
Gaia DR3 revealed a new class of neutron stars (NSs) in au-scale orbits with solar-type companions. How these 'Gaia NSs' form remains unclear, and constraining their intrinsic population properties is a necessary step toward understanding their origin. However, the current sample of 27 Gaia NS candidates is strongly biased by Gaia's astrometric sensitivity. In this work, we carefully model the Gaia selection function and incorporate it into a hierarchical Bayesian framework to infer the \textit{intrinsic} demographics of the Gaia NS population. We find that the population favors a decreasing period distribution with power-law slope $α_P=-0.75 \pm 0.35$, a visible-star mass distribution peaked near $M_1\approx 0.85~{\rm M_\odot}$ ($σ_{M_1} \approx 0.2~{\rm M_\odot}$), an NS mass distribution peaked near $M_{\rm NS}\approx 1.3~{\rm M_\odot}$ with a tail towards higher masses, and an eccentricity distribution weighted toward moderate-to-large eccentricities. The intrinsic space density is $n\approx120~{\rm kpc^{-3}}$ within 2 kpc, implying that only $\sim3\%$ of the local Gaia NS population has been discovered so far. Our forecasts predict that Gaia DR4 will increase the sample to $\sim300$-650 NS candidates, including access to longer orbital periods that will provide direct tests of formation models. Finally, we place Gaia NSs in the context of the broader Galactic NS population by comparing their intrinsic birth rate, lifetime, and size to other classes of isolated and binary NSs. Only 0.01% - 1% of all NSs are born into au-scale orbits with solar-type companions, making the birth rate of Gaia NSs 10 - 100 times smaller than that of high-mass X-ray binaries and broadly comparable to symbiotic X-ray binaries.
发表机构
- California Institute of Technology（加州理工学院）
- Texas Tech University（德克萨斯理工大学）
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