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arXiv 1204.6322astro-ph.EP
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碎片盘的无行星流体动力学模型中的尖偏心环

Sharp eccentric rings in planetless hydrodynamical models of debris disks

Wladimir Lyra, Marc J. Kuchner

摘要:

碎片盘不应完全没有气体,因为微行星和尘埃颗粒通过升华、光致解吸或碰撞放气产生了第二代气体,产生了一个尘埃与气体之比接近1的系统,其中流体动力学不能忽略。在这种结构中存在一种聚集不稳定性,迄今为止,这种不稳定性仅在一维不可压缩模型中进行了探索。我们进行了2D数值可压缩模型的磁盘与可比数量的气体和尘埃,以研究这种不稳定性的增长和发展。我们的模型解决了气体和尘埃的动量方程,以及能量和连续性方程。我们发现,从气体到尘埃牧羊人环的阻力的反作用,类似于碎片盘中观察到的,通常归因于假设的未被发现的行星的存在。我们还发现,这些环的偏心率,通常作为行星存在的令人信服的证据,实际上可以简单地解释为沿环传播的驻波。环支持一系列的振荡,其中一种特定的模式代表周转运动。表观偏心率与观测系统中的偏心率相匹配。这表明,行星的可能性,虽然令人兴奋,不一定需要解释这些系统。

英文摘要:

Debris disks should not be completely gas-free, since there is second generation gas from outgassing of planetesimals and dust grains via sublimation, photodesorption, or collisions, generating a system of dust-to-gas ratio close to unity, where hydrodynamics cannot be ignored. A clumping instability exists in this configuration, that has been hitherto explored only in one-dimensional, incompressible models. We performed 2D numerical compressible models of a disk with comparable amounts of gas and dust to study the growth and development of this instability. Our model solves the momentum equation for the gas and dust, together with energy and continuity equations. We uncover that the backreaction of the drag force from the gas onto the dust shepherds rings, similar to those observed in debris disks and usually attributed to the presence of hypothetical undetected planets. We also uncover that the eccentricity of these rings, usually presented as convincing evidence for the presence of a planet, can actually be simply explained by a standing wave propagating along the ring. The rings support a spectrum of oscillations, with one particular mode representing epicyclic motion. The apparent eccentricity matches the eccentricity in observed systems. This suggests that the planet possibility, though thrilling, is not necessarily required to explain these systems.

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