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arXiv 1601.03009astro-ph.EP
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螺旋密度波驱动下的原行星盘加热与演化

Protoplanetary Disk Heating and Evolution Driven by the Spiral Density Waves

Roman R. Rafikov

摘要:

一些原行星盘在散射光下的高分辨率成像显示,存在着明显振幅的全球螺旋臂,可能是由大质量行星或恒星伴星激发的。假设这些武器的密度波,演变成螺旋冲击,我们评估其对热力学,吸积和全球的磁盘演变的影响。我们推导出的直接(不可逆)加热,角动量输运,和质量吸积率引起的磁盘冲击的任意强度的解析表达式。我们发现这些过程是非常敏感的冲击振幅。集中在中等强度的波(密度跳跃的冲击$ΔΣ/Σ\sim 1$),我们表明相关的磁盘加热是可以忽略不计的(在$\sim 1\%$水平的能量预算)在被动的,照射的原行星盘上$\sim 100$ AU尺度,但变得重要的几个AU从恒星。与此同时,激波加热可能是激变变星、恒星X射线双星和超大质量黑洞双星盘中的一个重要(甚至是主导)能源,主要由粘性耗散加热。由整体螺旋激波引起的质量吸积相当于(或超过)由于粘性应力引起的质量流入。在$\sim 100$ AU的$\lesssim 0.5$ Myr中,以突出的全球螺旋为特征的原行星盘必须迅速演变。直接上限的磁盘演变的时间尺度可以建立通过测量的重力扭矩,由于从成像数据的螺旋臂。我们的研究结果表明,无论其起源,全球螺旋波必须是重要的代理商的原行星盘的演变。它们可能是盘扩散的一种有效机制,并可能与过渡盘现象有关。

英文摘要:

High-resolution imaging of some protoplanetary disks in scattered light reveals presence of the global spiral arms of significant amplitude, likely excited by massive planets or stellar companions. Assuming that these arms are density waves, evolving into spiral shocks, we assess their effect on the thermodynamics, accretion, and global evolution of the disk. We derive analytical expressions for the direct (irreversible) heating, angular momentum transport, and mass accretion rate induced by the disk shocks of arbitrary strength. We find these processes to be very sensitive to the shock amplitude. Focusing on the waves of moderate strength (density jump at the shock $ΔΣ/Σ\sim 1$) we show the associated disk heating to be negligible (contributing at $\sim 1\%$ level to the energy budget) in passive, irradiated protoplanetary disks on $\sim 100$ AU scales, but becoming important within several AU from the star. At the same time, shock heating can be a significant (or even dominant) energy source in disks of cataclysmic variables, stellar X-ray binaries, and supermassive black hole binaries, heated mainly by viscous dissipation. Mass accretion induced by the global spiral shocks is comparable to (or exceeds) the mass inflow due to viscous stresses. Protoplanetary disks featuring prominent global spirals must be evolving rapidly, in $\lesssim 0.5$ Myr at $\sim 100$ AU. A direct upper limit on the disk evolution timescale can be established via the measurement of the gravitational torque due to the spiral arms from the imaging data. Our findings suggest that, regardless of their origin, global spiral waves must be important agents of the protoplanetary disk evolution. They may serve as an effective mechanism of disk dispersal and could be related to the transitional disk phenomenon.

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