论文标题
GRB 180325a：灰尘粒度分布和星际铁纳米颗粒的贡献
GRB 180325A: dust grain-size distribution and interstellar iron nanoparticles contribution
论文作者
论文摘要
我们在$γ$ ray爆发（GRB）Afterglow的环境中为碳质和硅酸盐以及自由飞行的铁纳米颗粒建模了灰尘粒度分布，GRB 180325a。此GRB为$ z = 2.2486 $，具有对2175Å灭绝功能的明确检测，其中$ r_v = 4.58 $和$ a_v = 1.58 $。除了硅酸盐，多环芳烃（PAH）和石墨外，我们首次使用了铁纳米粒子晶粒大小分布来对观察到的GRB 180325a的灭绝曲线进行建模。我们使用232组硅酸盐，石墨，碳酸分子中的碳丰度（$ b_c $）以及自由飞行的纳米颗粒中的铁丰度（$ b _ {\ text {fe}} $）中，使用232组硅酸盐，石墨，碳丰度（$ b_c $）（$ B _ {\ text {fe}} $）。选择了这四个不同的排列以测试碳氢化合物中的铁纳米颗粒的显着性和碳丰度。我们的结果表明，铁纳米颗粒的贡献微不足道，并且存在碳丰富度的退化性，范围为$（0.0 \ leq b_c \ leq 0.7）\ times10^{ - 5} $，为观察到的GRB 180325A的灭绝曲线提供了最佳拟合。因此，我们赞成最简单的硅酸盐和多环芳烃模型。硅酸盐具有主导性，并有助于GRB灭绝曲线的整个波长范围，而石墨又有助于2175Å的凸起和紫外线灭绝。余辉的峰值光度（$ 1.5 \ times10^{51} $ ergs/s）表明可能发生了尘埃破坏。我们得出的结论是，有必要对其他潜在灭绝贡献者进行进一步的研究，特别是对于陡峭的紫外线灭绝。
We modelled dust grain-size distributions for carbonaceous and silicates dust, as well as for free-flying iron nanoparticles in the environment of a $γ$-ray burst (GRB) afterglow, GRB 180325A. This GRB, at $z=2.2486$, has an unambiguous detection of the 2175 Å extinction feature with $R_V=4.58$ and $A_V=1.58$. In addition to silicates, polycyclic aromatic hydrocarbons (PAH), and graphite, we used iron nanoparticles grain-size distributions for the first time to model the observed extinction curve of GRB 180325A. We fit the observed extinction for four model permutations, using 232 sets of silicates, graphite, carbon abundance in hydrocarbon molecules ($b_C$), and fraction of iron abundance in free-flying nanoparticles ($b_{\text{Fe}}$). These four different permutations were chosen to test iron nanoparticles significance and carbon abundance in hydrocarbons. Our results indicate that iron nanoparticles contribution is insignificant and there is a degeneracy of carbon abundances, with the range $(0.0 \leq b_C \leq 0.7)\times10^{-5}$ providing the best-fit to the observed extinction curve of GRB 180325A. We therefore favour the simplest model of silicates and polycyclic aromatic hydrocarbons. The silicates are dominant and contribute to the entire wavelength range of the GRB extinction curve while graphite contributes towards both the 2175 Å bump and the UV extinction. The afterglow peak luminosity ($1.5\times10^{51}$ ergs/s) indicates dust destruction may have taken place. We conclude that further investigations into other potential contributors of extinction are warranted, particularly for steep UV extinction.
