Context: White dwarf - Brown dwarf short period binaries (P$_{\rm orb}$ $\lesssim$ 2 hours) are some of the most extreme irradiated atmospheric environments known. These systems offer an opportunity to explore theoretical and modelling efforts of irradiated atmospheres different to typical hot Jupiter systems. Aims: We aim to investigate the three dimensional atmospheric structural and dynamical properties of the Brown dwarf WD0137-349B. Methods: We use the three dimensional GCM model Exo-FMS, with a dual-band grey radiative-transfer scheme to model the atmosphere of WD0137-349B. The results of the GCM model are post-processed using the three dimensional Monte Carlo radiative-transfer model \textsc{cmcrt}. Results: Our results suggest inefficient day-night energy transport and a large day-night temperature contrast for WD0137-349B. Multiple flow patterns are present, shifting energy asymmetrically eastward or westward depending on their zonal direction and latitude. Regions of overturning are produced on the western terminator. We are able to reproduce the start of the system near-IR emission excess at $\gtrsim$ 1.95 $\mu$m as observed by the GNIRS instrument. Our model over predicts the IR phase curve fluxes by factors of $\approx$1-3, but generally fits the shape of the phase curves well. Chemical kinetic modelling using \textsc{vulcan} suggests a highly ionised region at high altitudes can form on the dayside of the Brown dwarf. Conclusions: We present a first attempt at simulating the atmosphere of a short period White dwarf - Brown dwarf binary in a 3D setting. Further studies into the radiative and photochemical heating from the UV irradiation is required to more accurately capture the energy balance inside the Brown dwarf atmosphere. Cloud formation may also play an important role in shaping the emission spectra of the Brown dwarf.

中文翻译：

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受辐射褐矮星 WD 0137−349B 的简化 3D GCM 建模

背景：白矮星 - 褐矮星短周期双星（P$_{\rm orb}$ $\lesssim$ 2 小时）是已知的最极端的辐射大气环境之一。这些系统为探索不同于典型热木星系统的受辐射大气的理论和建模工作提供了机会。目的：我们旨在研究褐矮星 WD0137-349B 的三维大气结构和动力学特性。方法：我们使用三维 GCM 模型 Exo-FMS，采用双波段灰色辐射传输方案来模拟 WD0137-349B 的大气。GCM 模型的结果使用三维蒙特卡罗辐射传递模型 \textsc{cmcrt} 进行后处理。结果：我们的结果表明 WD0137-349B 的昼夜能量传输效率低下，并且昼夜温差较大。存在多种流动模式，根据其纬向和纬度向东或向西不对称地转移能量。在西部终结者上产生了翻转区域。正如 GNIRS 仪器所观察到的，我们能够在 $\gtrsim$ 1.95 $\mu$m 处重现系统的近红外发射过量的开始。我们的模型通过大约 1-3 美元的因子过度预测 IR 相位曲线通量，但通常很好地拟合相位曲线的形状。使用 \textsc{vulcan} 的化学动力学模型表明，在棕矮星的日侧可以形成高海拔的高度电离区域。结论：我们首次尝试在 3D 环境中模拟短期白矮星 - 褐矮星双星的大气。需要进一步研究来自紫外线照射的辐射和光化学加热，以更准确地捕捉褐矮星大气内部的能量平衡。云的形成也可能在塑造棕矮星的发射光谱方面发挥重要作用。