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arXiv 2306.02453astro-ph.HEastro-ph.SR
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含热传导的热吸积流的全局跨声速解

Global Transonic Solution of Hot Accretion Flow with Thermal Conduction

Samik Mitra, Sayyedeh Masoumeh Ghoreyshi, Amin Mosallanezhad, Shahram Abbassi, Santabrata Das

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12 pages, 8 figures; accepted for publication in MNRAS
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AI总结：

本研究针对低吸积率非旋转黑洞的低角动量热吸积流，采用饱和热传导通量与数值方法求解动力学方程，探究热传导对吸积流跨声速特性等的影响，并对比全局解与自相似解的差异，为解释盘外流提供参考。

摘要：

我们研究了热传导对以极低速率吸积质量的非旋转黑洞周围低角动量热吸积流（HAF）的影响。在此过程中，我们采用饱和形式的传导热通量，并利用数值方法求解了对应于稳态、轴对称、黏滞平流吸积流的动力学方程组。我们根据输入参数，即能量（$\varepsilon_0$）、角动量（$\ell_0$）、黏滞参数（$α$）以及调节热传导效应的饱和常数（$Φ_{\rm s}$），研究了吸积物质的动力学和热力学特性。我们发现，$Φ_{\rm s}$在决定全局吸积解的跨声速特性方面起着关键作用。一般而言，当$Φ_{\rm s}$增大时，临界点（$r_{\rm c}$）会远离黑洞，且流动变量会发生改变，尤其是在盘的外部区域。为了量化$Φ_{\rm s}$的物理可接受范围，我们将全局跨声速解与自相似解进行了比较，并观察到从全局解估算出的最大饱和常数（$Φ^{\rm max}_{\rm s}$）超过了由自相似形式体系推导出的饱和热传导极限（$Φ_{\rm sc}$）。此外，我们计算了$α$与$Φ^{\rm max}_{\rm s}$之间的相关性，发现全局解与自相似解之间存在大量不一致之处。进一步地，利用全局流动变量，我们计算了伯努利参数（$Be$），该参数在整个盘内始终为正，不过对于更高的$Φ_{\rm s}$，流动会变为弱束缚状态。最后，我们指出了这项工作在天体物理背景下解释非束缚盘发生质量损失/外流可能性的相关意义。

英文摘要：

We examine the effect of thermal conduction on the low-angular momentum hot accretion flow (HAF) around non-rotating black holes accreting mass at very low rate. While doing so, we adopt the conductive heat flux in the saturated form, and solve the set of dynamical equations corresponding to a steady, axisymmetric, viscous, advective accretion flow using numerical methods. We study the dynamical and thermodynamical properties of accreting matter in terms of the input parameters, namely energy ($\varepsilon_0$), angular momentum ($\ell_0$), viscosity parameter ($α$), and saturation constant ($Φ_{\rm s}$) regulating the effect of thermal conduction. We find that $Φ_{\rm s}$ plays a pivotal role in deciding the transonic properties of the global accretion solutions. In general, when $Φ_{\rm s}$ is increased, the critical point ($r_{\rm c}$) is receded away from the black hole, and flow variables are altered particularly in the outer part of the disc. To quantify the physically acceptable range of $Φ_{\rm s}$, we compare the global transonic solutions with the self-similar solutions, and observe that the maximum saturation constant ($Φ^{\rm max}_{\rm s}$) estimated from the global solutions exceeds the saturated thermal conduction limit ($Φ_{\rm sc}$) derived from the self-similar formalism. Moreover, we calculate the correlation between $α$ and $Φ^{\rm max}_{\rm s}$ and find ample disagreement between global solutions and self-similar solutions. Further, using the global flow variables, we compute the Bernoulli parameter ($Be$) which remains positive all throughout the disc, although flow becomes loosely unbound for higher $Φ_{\rm s}$. Finally, we indicate the relevance of this work in the astrophysical context in explaining the possibility of massloss/outflows from the unbound disc.

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