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arXiv 2402.02148astro-ph.EPastro-ph.GAastro-ph.SR
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年轻星协中的恒星伴星与类木行星

Stellar companions and Jupiter-like planets in young associations

R. Gratton, M. Bonavita, D. Mesa, S. Desidera, A. Zurlo, S. Marino, V. D'Orazi, E. Rigliaco, V. Nascimbeni, D. Barbato, G. Columba, V. Squicciarini

AI总结:

本研究扩展分析年轻邻近星协,发现恒星伴星和类木行星频率高,分别对应盘碎片化和核吸积,且类木行星频率随星协质量年龄降低。

摘要:

最近,我们结合高对比度成像和空间天体测量,发现类木行星在β Pic移动星群(BPMG)中,围绕那些其轨道可以稳定的恒星周围是频繁存在的,这引发了进一步的分析和讨论。我们将之前的分析扩展到其他年轻的邻近星协,以确定伴星(特别是类木行星)的频率、质量和间距,以及它们与星协质量和年龄的依赖关系。我们收集了关于伴星的可用数据,包括通过视觉观测、掩星、光谱和天体测量所揭示的伴星。我们确定了搜索完备性,发现对于恒星伴星,完备性非常高,而对于类木行星伴星,完备性修正仍然很大。一旦将这些修正考虑在内,我们发现伴星的频率很高,无论是恒星伴星(>0.52±0.03)还是类木行星伴星(0.57±0.11)。这两个群体被一个对应于褐矮星沙漠的间隙所分隔。在大质量伴星群体中,我们发现了频率、间距和质量比随恒星质量的变化趋势。行星伴星堆积在冰线外侧的区域,并且一旦考虑完备性,我们发现它们频繁存在。类木行星的频率随着星协的整体质量以及可能的年龄的增加而降低。我们初步将这两个群体分别归因于盘碎片化和核吸积。半长轴小于1000天文单位的恒星伴星的分布,可以很好地由盘碎片化形成的简单模型所重现。观察到的随恒星质量的变化趋势,可以通过大质量恒星盘上更短但更强烈的吸积阶段,以及太阳型恒星上更稳定和持续的吸积来解释。对于类木行星群体随星协质量和年龄变化的趋势,我们简要讨论了可能的解释。

英文摘要:

Recently, combining high-contrast imaging and space astrometry we found that Jupiter-like (JL) planets are frequent in the beta Pic moving group (BPMG) around those stars where their orbit can be stable, prompting further analysis and discussion. We broaden our previous analysis to other young nearby associations to determine the frequency, mass, and separation of companions in general and JL in particular and their dependencies on the mass and age of the associations. We collected available data about companions including those revealed by visual observations, eclipses, spectroscopy, and astrometry. We determined search completeness and found that it is very high for stellar companions, while completeness corrections are still large for JL companions. Once these corrections are included, we found a high frequency of companions, both stellar (>0.52+/-0.03) and JL (0.57+/-0.11). The two populations are separated by a gap that corresponds to the brown dwarf desert. Within the population of massive companions, we found trends in frequency, separation, and mass ratios with stellar mass. Planetary companions pile up in the region just outside the ice line and we found them to be frequent once completeness was considered. The frequency of JL planets decreases with the overall mass and possibly the age of the association. We tentatively identify the two populations as due to disk fragmentation and core accretion, respectively. The distributions of stellar companions with a semi-major axis <1000 au is well reproduced by a simple model of formation by disk fragmentation. The observed trends with stellar mass can be explained by a shorter but much more intense phase of accretion onto the disk of massive stars and by a more steady and prolonged accretion on solar-type stars. Possible explanations for the trends in the population of JL planets with association mass and age are briefly discussed.

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