White dwarf (WD) binary mergers are possible progenitors to a number of unusual stars and transient phenomena, including type Ia supernovae. To date, simulations of mergers have not included magnetic fields, even though they are believed to play a significant role in the evolution of the merger remnant. We simulated a 0.625 - 0.65 $M_{\odot}$ carbon-oxygen WD binary merger in the magnetohydrodynamic moving mesh code Arepo. Each WD was given an initial dipole field with a surface value of $\sim10^3$ G. As in simulations of merging double neutron star binaries, we find exponential field growth within Kelvin-Helmholtz instability-generated vortices during the coalescence of the two stars. The final field has complex geometry, and a strength $>10^{10}$ G at the center of the merger remnant. Its energy is $\sim2\times10^{47}$ ergs, $\sim0.2$% of the remnant's total energy. The strong field likely influences further evolution of the merger remnant by providing a mechanism for angular momentum transfer and additional heating, potentially helping to ignite carbon fusion.
Protostellar disks in their natural habitat -- the formation of protostars and their accretion disks in the turbulent and magnetized interstellar medium
Double White Dwarf Mergers as Progenitors of Long-Period Transients
Instituto Tecnológico de Aeronáutica（巴西航空研究院）；University of Wisconsin-Milwaukee（威斯康星大学密尔沃基分校）；Universidade Federal do Espírito Santo（圣埃斯皮里图联邦大学）；Instituto Nacional de Pesquisas Espaciais（国家空间研究所）；Centro Brasileiro de Pesquisas Físicas（巴西物理研究中心）；ICRANet（国际相对论天体物理中心网络）；Universidade Federal do Cariri（卡鲁里联邦大学）；ICRA（国际相对论天体物理中心）；INAF（意大利国家天体物理研究所）；Universidade de São Paulo（圣保罗大学）；San Diego State University（圣地亚哥州立大学）
No double detonations but core carbon ignitions in high-resolution, grid-based simulations of binary white dwarf mergers
我们研究了大质量双星白矮星系统合并的剧烈相。我们的目标是描述爆炸燃烧发生的条件，并确定Ia型超新星可能的爆炸机制。我们的模型系统的主要成分是碳氧（C/O）白矮星，而次要成分是由C/O或纯氦组成。我们占潮汐的影响，在初始条件下，在一个自洽的方式，并考虑最初良好分离的系统缓慢的inspiral率。我们研究了合并的演变使用自适应网格细化，反应，欧拉代码在三维空间，假设对称的轨道平面。我们使用一个同向旋转的参考系，以尽量减少数值扩散的影响，并使用多重网格的方法解决自重。我们发现了一种新的爆轰机制，在C/O合并与大量的初级。在这里，爆炸发生在原核的核心，并依赖于潮汐加热，吸积加热和自加热的综合作用，由于核燃烧。爆炸结构的成分分层，与一个反向冲击形成的密集喷出物的表面。在其他地方没有报道过这种冲击的存在。爆炸能量（$1.6\times 10^{51}$ erg）和$^{56}$ Ni质量（0.86 M $_\odot$）与超新星Ia在光度分布的亮端一致，近似下降率为$Δm_{15}(B)\approx 0.99$。我们的研究不支持双爆轰的情况下，0.6 M $_\odot$氦次级和0.9 M $_\odot$主要的系统。虽然吸积的氦爆炸，但它未能点燃边界层底部或原爆堆芯的碳。
