AI 中文总结
本文通过二维NLTE辐射转移模拟研究Ia型超新星双爆模型光球层阶段的多维与NLTE效应，发现NLTE处理可改善与正常Ia型超新星的符合度，但当前氦壳质量过大导致多数视线上存在过度线遮蔽问题。
AI 中文摘要
以往的辐射转移计算表明，多维性和非局部热动平衡（NLTE）效应都会影响Ia型超新星爆炸模型合成可观测量的预测。本文针对一个具有1倍太阳质量（M$_{\rm{\u2299}}$）碳氧核心和0.02倍太阳质量（M$_{\rm{\u2299}}$）氦壳的双爆模型，开展了光球层阶段的二维NLTE辐射转移模拟。预测的可观测量显示，与观测比较相关的尺度上，偏离球对称性和局部热动平衡的效应均十分显著。NLTE处理会导致光谱能量分布更蓝、光学波段光变曲线衰减更慢、近红外光变曲线形状发生变化，以及关键光谱特征的演化出现差异。尽管该模型预测存在显著的观测视角变化，但在峰值前，变化幅度并未受到NLTE效应的显著影响；然而在峰值后，本文的二维NLTE模拟在光谱中仍保留着强烈的观测视角依赖性，而采用近似NLTE处理对相同抛射体模型开展的模拟则预测光谱观测视角变化显著降低。NLTE处理主要由于模拟中电离态升高，使得与正常Ia型超新星的符合度得到改善，但近红外次极大的缺失表明，峰值后抛射体相对于观测仍处于过电离状态。尽管符合度有所提升，但仍有大量观测视角表现出过度的线遮蔽，表明当前模型的0.02倍太阳质量氦壳质量过大，无法在大多数视线上复现正常Ia型超新星。
英文摘要
Previous radiative transfer calculations have shown that both multi-dimensionality and NLTE (non local thermodynamic equilibrium) effects impact the synthetic observables predicted for Type Ia supernova explosion models. Here we carry out a 2D NLTE radiative transfer simulation in the photospheric phase for a double detonation model with a 1 M$_{\odot}$ carbon-oxygen core and 0.02 M$_{\odot}$ helium shell. The predicted observables demonstrate that departures from both spherical symmetry and local thermodynamic equilibrium are significant on scales relevant to comparisons with observations. The NLTE treatment leads to a bluer spectral energy distribution, more slowly declining optical-band light curves, changes to the near-infrared light curve shapes, and differences in the evolution of key spectral features. Although substantial viewing-angle variation is predicted for the model, the scale of the variation is not significantly impacted by NLTE effects up to peak. However, after peak, our 2D NLTE simulation retains a strong viewing-angle dependence in its spectra whereas our simulation of the same ejecta model using an approximate NLTE treatment predicts significantly reduced spectroscopic viewing-angle variation. The NLTE treatment leads to improved agreement with normal Type Ia supernovae, primarily due to the increased ionisation state of the simulation, although the absence of a secondary near-infrared maximum suggests that the ejecta remain over-ionised relative to observations after peak. Despite the improved agreement, many viewing angles still show excessive line blanketing, suggesting that the 0.02 M$_{\odot}$ helium-shell mass of the current model is too large to reproduce normal Type Ia supernovae over the majority of lines of sight.
Comments18 pages, 12 figures. Submitted to MNRAS
