超越观测所见：Gaia天体测量致密天体双星的分层推断
Beyond what's observed: hierarchical inference of Gaia astrometric compact-object binaries
- California Institute of Technology（加州理工学院）
- University of Toronto（多伦多大学）
- Max-Planck Institute for Astronomy（马克斯·普朗克天文学研究所）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究开发分层贝叶斯模型，利用Gaia天体测量数据推断白矮星-主序星双星的内在性质，发现轨道周期幂律分布、白矮星质量峰值及非零偏心率，为双星演化提供经验基准。
AI中文摘要：
Gaia任务的天体测量揭示了大量且均匀的包含致密天体的双星种群，其中包括超过3000个轨道周期为$P_{\rm orb}\sim100$--$1000$天的白矮星-主序星（WDMS）双星。这些双星中的大多数可能经历了来自渐近巨分支星的物质转移，但其演化历史仍不确定。我们开发了一个分层贝叶斯推断模型，在考虑测量不确定性和巡天选择函数的同时，约束Gaia WDMS双星种群的内在性质。我们推断出轨道周期、组分质量和偏心率的分布，以及总空间密度。我们发现内在轨道周期分布遵循下降的幂律，$p(P_{\rm orb})\propto P_{\rm orb}^{-0.445\pm0.048}$，白矮星质量分布在$0.6\\,M_\odot$附近尖锐峰值，只有约1%的系统拥有质量大于$0.8\\,M_\odot$的白矮星。推断的主序星质量分布相对平坦，直至约$0.3\\,M_{\odot}$，如果该种群主要由具有固定临界质量比的稳定物质转移产物主导，这是出乎意料的。偏心率分布在非零值$e=0.046\pm0.001$处达到峰值，表明不完整的圆化或偏心率激发。我们推断在Gaia DR3探测的参数空间中，WDMS双星的银道面空间密度约为$3\times10^4\\,{\rm kpc}^{-3}$。这些性质为未来约束双星演化模型的工作提供了经验基准。我们还将该框架应用于Gaia黑洞和中子星双星，推断出在2 kpc内分别存在$30^{+66}_{-20}$和$614^{+203}_{-149}$个这样的系统。该框架将能够对从Gaia DR4预期获得的更大天体测量轨道目录中识别出的广泛系统进行详细的种群级约束。
英文摘要：
Astrometry from the Gaia mission has revealed a large and homogeneous population of binaries containing compact objects, including more than 3000 white dwarf--main sequence (WDMS) binaries with orbital periods of $P_{\rm orb}\sim100$--$1000$ d. Most of these binaries likely underwent mass transfer from asymptotic giant branch donors, but their evolutionary histories remain uncertain. We develop a hierarchical Bayesian inference model to constrain the intrinsic properties of the Gaia WDMS binary population while accounting for measurement uncertainties and the survey selection function. We infer the distributions of orbital period, component masses, and eccentricity, as well as the total space density. We find that the intrinsic orbital-period distribution follows a declining power law, $p(P_{\rm orb})\propto P_{\rm orb}^{-0.445\pm0.048}$, and the WD mass distribution is sharply peaked near $0.6\,M_\odot$, with only ~1% of systems hosting WDs more massive than $0.8\,M_\odot$. The inferred MS-star mass distribution is relatively flat down to ~$0.3\,M_{\odot}$, which is unexpected if the population is dominated by products of stable mass transfer with a fixed critical mass ratio. The eccentricity distribution peaks at a nonzero value, $e=0.046\pm0.001$, suggesting incomplete circularization or eccentricity excitation. We infer a midplane space density of ~$3\times10^4\,{\rm kpc}^{-3}$ for WDMS binaries in the parameter space probed by Gaia DR3. These properties provide empirical benchmarks for future work to constrain binary evolution models. We also apply the framework to Gaia black hole and neutron star binaries, inferring that $30^{+66}_{-20}$ and $614^{+203}_{-149}$ such systems exist within 2 kpc, respectively. This framework will enable detailed population-level constraints on a wide range of systems identified from the much larger catalog of astrometric orbits expected from Gaia DR4.
