GENERALIZED SIMILARITY FOR ACCRETION/DECRETION DISKS
GENERALIZED SIMILARITY FOR ACCRETION/DECRETION DISKS
复制标题
吸积盘/吸积盘的广义相似性
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
R. Rafikov
中科院分区：
文献类型：
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作者：
R. Rafikov
排气（或外）盘是由于内应力而自由膨胀到大半径的气体盘。它们预计会在潮汐破坏事件中自然出现，在Be恒星周围，在质量损失后的主序双星中，由于超新星后退等。它们的演化在理论上有两种情况：当中心物体不对圆盘施加扭矩时（传统吸积盘的标准假设），或者当圆盘中心没有质量流入（或流出）时。然而，许多天体物理对象——环双星盘、Be星、以螺旋桨方式吸积的中子星等——在盘中心的非零吸积（或质量抛射）同时具有非零扭矩。我们给出了这类圆盘（线性和非线性）在自相似状态下的演化的一般描述，该状态下圆盘应随时间渐近收敛。我们确定了一个相似参数λ，它与中心质量吸积被非零中心扭矩抑制的程度唯一相关。已知的圆盘解对应于λ的两个离散值，而我们的新解涵盖了其物理允许值的连续体，对应于中心物体的吸积或质量抛射。λ与中心和转矩之间也建立了直接关系。我们描述了不同λ下吸积盘各种特征的时间演化，并表明吸积盘的可观测性质（光谱和光度演化）总体上不同于没有中心转矩的标准吸积盘。
Decretion (or external) disks are gas disks freely expanding to large radii due to their internal stresses. They are expected to naturally arise in tidal disruption events, around Be stars, in mass-losing post-main-sequence binaries, as a result of supernova fallback, etc. Their evolution is theoretically understood in two regimes: when the central object does not exert torque on the disk (a standard assumption for conventional accretion disks) or when no mass inflow (or outflow) occurs at the disk center. However, many astrophysical objects—circumbinary disks, Be stars, neutron stars accreting in a propeller regime, etc.—feature non-zero torque simultaneously with the non-zero accretion (or ejection of mass) at the disk center. We provide a general description for the evolution of such disks (both linear and nonlinear) in the self-similar regime, to which the disk should asymptotically converge with time. We identify a similarity parameter λ, which is uniquely related to the degree, to which the central mass accretion is suppressed by the non-zero central torque. The known decretion disk solutions correspond to the two discrete values of λ, while our new solutions cover a continuum of its physically allowed values, corresponding to either accretion or mass ejection by the central object. A direct relationship between λ and central and torque is also established. We describe the time evolution of the various disk characteristics for different λ, and show that the observable properties (spectrum and luminosity evolution) of the decretion disks, in general, are different from the standard accretion disks with no central torque.