论文标题
部分可观测时空混沌系统的无模型预测
Cosmic rays from massive star clusters : A close look at Westerlund 1
论文作者
论文摘要
我们研究了宇宙射线（CR）加速度在巨大的紧凑型星簇Westerlund 1中的效果，鉴于其最近在$γ$ rays中的检测。最近的观察结果显示，CR能量密度的$ 1/R $径向分布。在这里，我们从理论上研究了此轮廓是否可以帮助区分（1）Star群集恒星风力驱动的冲击中的连续CR加速度和（2）多个超新星冲击中的离散CR加速度 - 在文献中经常在文献中进行辩论。使用理想化的两流体模拟并探索不同的加速位点和扩散系数，我们获得了CR能量密度曲线和发光度，以找到$γ$ -Ray观测值的最佳匹配。我们发现，从观察到$γ$ ray亮度和质量的观察结果的推断CR能量密度曲线可能与真实的径向谱大不相同。 CR acceleration at either the cluster core region or the wind termination shock can explain the observations, if the diffusion coefficient is $κ_{\rm cr}\sim 10^{27}$ cm$^2$ s$^{-1}$ and a fraction of $\approx 10\%-20\%$ of the shock power/post-shock pressure is deposited into the CR component.我们还研究了导致CR加速度的离散超新星（SN）爆炸的可能性，并发现每$ \ sim 0.03 $ MYR的注入率为1 Sn，人们可以解释观察到的$γ$ ray概况。仅当导热率接近Spitzer值时，这种多种SN方案与X射线观测一致。
We study the effect of cosmic ray (CR) acceleration in the massive compact star cluster Westerlund 1 in light of its recent detection in $γ$-rays. Recent observations reveal a $1/r$ radial distribution of the CR energy density. Here we theoretically investigate whether or not this profile can help to distinguish between (1) continuous CR acceleration in the star cluster stellar wind-driven shocks and (2) discrete CR acceleration in multiple supernovae shocks -- which are often debated in the literature. Using idealized two-fluid simulations and exploring different acceleration sites and diffusion coefficients, we obtain the CR energy density profile and luminosity to find the best match for the $γ$-ray observations. We find that the inferred CR energy density profiles from observations of $γ$-ray luminosity and mass can be much different from the true radial profile. CR acceleration at either the cluster core region or the wind termination shock can explain the observations, if the diffusion coefficient is $κ_{\rm cr}\sim 10^{27}$ cm$^2$ s$^{-1}$ and a fraction of $\approx 10\%-20\%$ of the shock power/post-shock pressure is deposited into the CR component. We also study the possibility of discrete supernovae (SN) explosions being responsible for CR acceleration and find that with an injection rate of 1 SN in every $\sim 0.03$ Myr, one can explain the observed $γ$-ray profile. This multiple SN scenario is consistent with X-ray observations only if the thermal conductivity is close to the Spitzer value.
