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Outbursts in Global Protoplanetary Disk Simulations
The Astrophysical Journal ( IF 4.9 ) Pub Date : 2020-05-22 , DOI: 10.3847/1538-4357/ab8bd8 Kundan Kadam 1 , Eduard Vorobyov 2, 3 , Zsolt Regly 1 , gnes Kspl 1, 4, 5 , Pter brahm 1, 5
The Astrophysical Journal ( IF 4.9 ) Pub Date : 2020-05-22 , DOI: 10.3847/1538-4357/ab8bd8 Kundan Kadam 1 , Eduard Vorobyov 2, 3 , Zsolt Regly 1 , gnes Kspl 1, 4, 5 , Pter brahm 1, 5
Affiliation
While accreting through a circumstellar disk, young stellar objects are observed to undergo sudden and powerful accretion events known as FUor or EXor outbursts. Although such episodic accretion is considered to be an integral part of the star formation process, the triggers and mechanisms behind them remain uncertain. We conducted global numerical hydrodynamics simulations of protoplanetary disk formation and evolution in the thin-disk limit, assuming both magnetically layered and fully magnetorotational instability (MRI)-active disk structure. In this paper, we characterize the nature of the outbursts occurring in these simulations. The instability in the dead zone of a typical layered disk results in "MRI outbursts". We explore their progression and their dependence on the layered disk parameters as well as cloud core mass. The simulations of fully MRI-active disks showed an instability analogous to the classical thermal instability. This instability manifested at two temperatures--above approximately 1400 K and 3500 K--due to the steep dependence of Rosseland opacity on the temperature. The origin of these thermally unstable regions is related to the bump in opacity resulting from molecular absorption by water vapor and may be viewed as a novel mechanism behind some of the shorter duration accretion events. Although we demonstrated local thermal instability in the disk, more investigations are needed to confirm that a large-scale global instability will ensue. We conclude that the magnetic structure of a disk, its composition, as well as the stellar mass, can significantly affect the nature of episodic accretion in young stellar objects.
中文翻译:
全球原行星盘模拟中的爆发
在通过星周盘吸积时,观察到年轻的恒星会经历突然而强大的吸积事件,称为 FUor 或 EXor 爆发。尽管这种偶发性吸积被认为是恒星形成过程的一个组成部分,但其背后的触发因素和机制仍然不确定。我们对原行星盘在薄盘极限内的形成和演化进行了全球数值流体动力学模拟,假设有磁性分层和完全磁旋转不稳定性 (MRI) 活动盘结构。在本文中,我们描述了这些模拟中发生的爆发的性质。典型分层磁盘死区的不稳定性导致“MRI 爆发”。我们探索了它们的进展及其对分层磁盘参数以及云核质量的依赖。完全 MRI 活性磁盘的模拟显示出类似于经典热不稳定性的不稳定性。由于 Rosseland 不透明度对温度的严重依赖,这种不稳定性表现在两个温度(大约 1400 K 和 3500 K 以上)。这些热不稳定区域的起源与水蒸气分子吸收导致的不透明度升高有关,并且可能被视为一些持续时间较短的吸积事件背后的新机制。尽管我们证明了圆盘中的局部热不稳定性,但还需要更多的调查来确认大规模的全球不稳定性将随之而来。我们得出结论,磁盘的磁性结构、其组成以及恒星质量可以显着影响年轻恒星天体中偶发吸积的性质。
更新日期:2020-05-22
中文翻译:
全球原行星盘模拟中的爆发
在通过星周盘吸积时,观察到年轻的恒星会经历突然而强大的吸积事件,称为 FUor 或 EXor 爆发。尽管这种偶发性吸积被认为是恒星形成过程的一个组成部分,但其背后的触发因素和机制仍然不确定。我们对原行星盘在薄盘极限内的形成和演化进行了全球数值流体动力学模拟,假设有磁性分层和完全磁旋转不稳定性 (MRI) 活动盘结构。在本文中,我们描述了这些模拟中发生的爆发的性质。典型分层磁盘死区的不稳定性导致“MRI 爆发”。我们探索了它们的进展及其对分层磁盘参数以及云核质量的依赖。完全 MRI 活性磁盘的模拟显示出类似于经典热不稳定性的不稳定性。由于 Rosseland 不透明度对温度的严重依赖,这种不稳定性表现在两个温度(大约 1400 K 和 3500 K 以上)。这些热不稳定区域的起源与水蒸气分子吸收导致的不透明度升高有关,并且可能被视为一些持续时间较短的吸积事件背后的新机制。尽管我们证明了圆盘中的局部热不稳定性,但还需要更多的调查来确认大规模的全球不稳定性将随之而来。我们得出结论,磁盘的磁性结构、其组成以及恒星质量可以显着影响年轻恒星天体中偶发吸积的性质。