圆盘不稳定性形成的巨行星的演化轨迹
Evolutionary tracks of giant planets formed by disk instability
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中文总结 AI 辅助
本研究通过MESPA代码模拟圆盘不稳定性形成的巨行星演化，发现金属丰度是质量推断的关键不确定性来源，其演化轨迹与部分实测巨行星质量一致，且无法仅靠光度区分两种形成途径。
中文摘要 AI 辅助
巨行星的演化取决于其形成历史。尽管已有若干演化模型将核吸积形成行星的过程与长期演化自洽地关联起来，但针对圆盘不稳定性形成的行星的此类模型仍有所欠缺。我们对圆盘不稳定性形成的巨行星的演化进行模拟，在统一数值框架中追踪其演化过程，包括坍缩前阶段、动力学坍缩及长期收缩阶段。我们使用MESPA代码进行演化模拟，该代码经过修改后可对坍缩前阶段的气体团块进行建模。我们考虑的行星质量范围为1至12倍木星质量，金属丰度范围为原太阳值的0.5至2倍。我们证实，坍缩前时标强烈依赖于行星质量，且动力学坍缩后，这些天体进入持续数十亿年的长期收缩状态。我们表明，金属丰度是由年龄-光度关系推导质量时不确定性的主要来源。对于此处考虑的金属丰度范围，我们发现，在给定年龄和光度测量值的情况下，推断质量的差异可达1.5倍木星质量。我们发现，我们的演化轨迹预测的质量与HR 8799 e、AF Lep b、Beta Pic b及Beta Pic c的实测动力学质量约束一致。我们还表明，核吸积和圆盘不稳定性均可导致非常相似的长期演化轨迹。我们的模型与动力学质量测量结果的一致性表明，圆盘不稳定性仍是巨系外行星的可行形成途径。仅靠光度演化无法区分两种形成途径。最后，我们建议，从年轻巨行星的光度推断其质量时，必须考虑行星金属丰度，因为它会显著影响行星的演化。
英文摘要
The evolution of giant planets depends on their formation history. While several evolutionary models self-consistently link planet formation by core accretion to long-term evolution, such models for planets formed by disk instability are lacking. We simulate the evolution of giant planets formed by disk instability and follow their evolution including the pre-collapse phase, dynamical collapse, and long-term contraction in a unified numerical framework. The evolution is simulated using the MESPA code with modifications that allow us to model gas clumps in the pre-collapse phase. We consider masses between 1 and 12 Jupiter masses and metallicities ranging from 0.5 to 2 times the protosolar value. We confirm that the pre-collapse timescale strongly depends on the planetary mass, and that after dynamical collapse the objects reach a state of long-term contraction which lasts for billions of years. We show that metallicity is a major source of uncertainty in mass estimates derived from the age-luminosity relations. For the metallicity range considered here, we find that for a given measurement of age and luminosity the difference in the inferred mass can be up to 1.5 Jupiter masses. We find that our evolution tracks predict masses that are consistent with the measured dynamical mass constraints for HR 8799 e, AF Lep b, Beta Pic b and Beta Pic c. We also show that both core accretion and disk instability can lead to very similar long-term evolutionary tracks. The agreement between our models and dynamical mass measurements suggests that disk instability remains a viable formation pathway for giant exoplanets. The luminosity evolution alone cannot distinguish between the two formation pathways. Finally, we suggest that planetary metallicity must be taken into account when inferring the masses of young giant planets from their luminosities, as it significantly affects their evolution.
