基于网格和SPH的二元传质和合并模拟的比较
A Comparison of Grid-Based and SPH Binary Mass-Transfer and Merger Simulations
摘要：
目前，人们对双简并双星合并的结果和天体物理意义产生了极大的兴趣。在通常采用的近似中，这类双星的组成部分用指数n=3/2的多面体表示。我们提出了详细的比较恒星质量转移和合并模拟的多变双星，已经进行了两个非常不同的数值算法-有限体积的“网格”代码和光滑粒子流体动力学（SPH）代码。我们发现，有协议的演变和中间阶段的最终结果，如果每个代码的初始条件被选择为尽可能接近匹配。我们发现，即使有密切匹配的初始设置，它所需要的时间，以达到一个和谐的演变不同的两个代码之间，因为接触的初始深度不能完全匹配。SPH一般倾向于产生更高的传质速率和更快的最终结果。我们还提出了从两个不同的能量方程计算的模拟的比较：在一个系列中，我们假设一个多方状态方程和在其他系列的理想气体状态方程。在后一系列的模拟中，大气层在吸积体周围形成，可以交换角动量并导致轨道角动量更快地损失。在这里提出的模拟中，理想状态方程的效果是使SPH和网格模拟中的二进制不稳定，但该效果在网格代码中更明显。
英文摘要：
Currently there is great interest in the outcomes and astrophysical implications of mergers of double degenerate binaries. In a commonly adopted approximation, the components of such binaries are represented by polytropes with an index n=3/2. We present detailed comparisons of stellar mass-transfer and merger simulations of polytropic binaries that have been carried out using two very different numerical algorithms --- a finite-volume "grid" code and a smoothed-particle hydrodynamics (SPH) code. We find that there is agreement in both the ultimate outcomes of the evolutions and the intermediate stages if the initial conditions for each code are chosen to match as closely as possible. We find that even with closely matching initial setups, the time it takes to reach a concordant evolution differs between the two codes because the initial depth of contact cannot be matched exactly. There is a general tendency for SPH to yield higher mass transfer rates and faster evolution to the final outcome. We also present comparisons of simulations calculated from two different energy equations: in one series we assume a polytropic equation of state and in the other series an ideal gas equation of state. In the latter series of simulations an atmosphere forms around the accretor which can exchange angular momentum and cause a more rapid loss of orbital angular momentum. In the simulations presented here, the effect of the ideal equation of state is to de-stabilize the binary in both SPH and grid simulations, but the effect is more pronounced in the grid code.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
