论文标题
观察性的约束在$^{26} $ Al在行星形成环境中的可能性
Observational constraints on the likelihood of $^{26}$Al in planet-forming environments
论文作者
论文摘要
最近的工作表明，$^{26} $ al可能会确定地面系外行星中的水预算，因为其放射性衰减脱水的行星可能会导致岩石成分。在这里，我考虑了在星系和典型的星形形成环境中观察到的$^{26} $ al的分布，以估计行星形成期间$^{26} $ allichment的可能性。我不假定太阳系特定的约束，因为我对通常对系外行星的富集感兴趣。观察结果表明，高质量恒星主导着$^{26} $ al的产量，其风和超新星的贡献几乎相等。 $^{26} $ al的丰度可与高质量恒星形成区域的早期太阳系中的丰度相媲美，大多数恒星（以及大多数行星）形式。这些高丰度似乎维持了几名MYR，比0.7 Myr半衰期更长。观察到的散装$^{26} $ al速度比风和超新星预期的速度要慢。这些观察结果与典型的模型假设不一致，即$^{26} $ al是由于超新星和风的高速质量损失即时提供的。定期补充$^{26} $ al，尤其是当与高质量星形成络合物中常见的小年龄差异相结合时，可能会大大增加暴露于$^{26} $ al的恒星/行星形成系统的数量。曝光并不意味着富集，而是$^{26} $ al的速度较慢的速度可能会更改纳入行星形成材料的分数。总之，这表明岩石行星形成的条件并不罕见，也不是无处不在的，因为像金牛座这样的小区域缺乏高质量的恒星来产生$^{26} $ al可能不太可能形成岩石行星。我以建议未来研究的建议指导结束。
Recent work suggests that $^{26}$Al may determine the water budget in terrestrial exoplanets as its radioactive decay dehydrates planetesimals leading to rockier compositions. Here I consider the observed distribution of $^{26}$Al in the Galaxy and typical star-forming environments to estimate the likelihood of $^{26}$Al enrichment during planet formation. I do not assume Solar-System-specific constraints as I am interested in enrichment for exoplanets generally. Observations indicate that high-mass stars dominate the production of $^{26}$Al with nearly equal contributions from their winds and supernovae. $^{26}$Al abundances are comparable to those in the early Solar System in the high-mass star-forming regions where most stars (and thereby most planets) form. These high abundances appear to be maintained for a few Myr, much longer than the 0.7 Myr half-life. Observed bulk $^{26}$Al velocities are an order of magnitude slower than expected from winds and supernovae. These observations are at odds with typical model assumptions that $^{26}$Al is provided instantaneously by high velocity mass loss from supernovae and winds. Regular replenishment of $^{26}$Al especially when coupled with the small age differences that are common in high-mass star-forming complexes, may significantly increase the number of star/planet-forming systems exposed to $^{26}$Al. Exposure does not imply enrichment, but the order of magnitude slower velocity of $^{26}$Al may alter the fraction that is incorporated into planet-forming material. Together, this suggests that the conditions for rocky planet formation are not rare, nor are they ubiquitous, as small regions like Taurus that lack high-mass stars to produce $^{26}$Al may be less likely to form rocky planets. I conclude with suggested directions for future studies.
