Investigating the Lower Mass Gap with Low-mass X-Ray Binary Population Synthesis
Investigating the Lower Mass Gap with Low-mass X-Ray Binary Population Synthesis
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DOI：
10.3847/1538-4357/ace9d9
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发表时间：
2022-09
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影响因子：
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通讯作者：
Jared C. Siegel;Ilia Kiato;V. Kalogera;C. Berry;T. Maccarone;K. Breivik;J. Andrews;S. Bavera
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作者：
Jared C. Siegel;Ilia Kiato;V. Kalogera;C. Berry;T. Maccarone;K. Breivik;J. Andrews;S. Bavera
低质量黑洞x射线双星（lmxb）和射电脉冲星的质量测量已经被用来确定最大质量中子星（NSs）和最小质量黑洞（BHs）之间的差距。lmxb的黑洞质量测量通常只能用于瞬态系统：爆发期可以通过全天x射线监测器进行检测，而静止期可以测量低质量供体的径向速度。我们定量地研究了由于黑洞质量测量的瞬态行为要求而产生的选择偏差。利用快速人口综合模拟（COSMIC）、详细的双星演化模型（MESA）和瞬态行为的盘不稳定性模型，我们证明了瞬态LMXB选择效应引入了观测偏差，并可以抑制观测样本中的质量间隙黑洞。然而，我们发现在LMXB阶段，通过吸积引起的NS坍缩形成了具有质量间隙的瞬态LMXB，这与观测结果不一致。这些结果对二元演化处方的变化具有鲁棒性。这种吸积引起的坍缩种群的重要性取决于最大NS出生质量MNS，出生- max。为了反映观测到的低质量黑洞的缺乏，COSMIC和MESA模型倾向于MNS，birth - max > 2M⊙。在没有进一步的观测偏差的情况下，我们的结果表明，需要额外的物理与LMXB的形成和演化建模有关。
Mass measurements from low-mass black hole X-ray binaries (LMXBs) and radio pulsars have been used to identify a gap between the most massive neutron stars (NSs) and the least massive black holes (BHs). BH mass measurements in LMXBs are typically only possible for transient systems: outburst periods enable detection via all-sky X-ray monitors, while quiescent periods enable radial velocity measurements of the low-mass donor. We quantitatively study selection biases due to the requirement of transient behavior for BH mass measurements. Using rapid population synthesis simulations (COSMIC), detailed binary stellar-evolution models (MESA), and the disk instability model of transient behavior, we demonstrate that transient LMXB selection effects introduce observational biases, and can suppress mass-gap BHs in the observed sample. However, we find a population of transient LMXBs with mass-gap BHs form through accretion-induced collapse of an NS during the LMXB phase, which is inconsistent with observations. These results are robust against variations of binary evolution prescriptions. The significance of this accretion-induced collapse population depends upon the maximum NS birth mass MNS,birth−max . To reflect the observed dearth of low-mass BHs, COSMIC and MESA models favor MNS,birth−max≲2M⊙ . In the absence of further observational biases against LMXBs with mass-gap BHs, our results indicate the need for additional physics connected to the modeling of LMXB formation and evolution.