星际无碰撞激波的Balmer双线结构

Balmer Double Line Produced by Collisionless Shock in Supernova Remnants

Balmer发射线是研究星际无碰撞激波物理性质的重要途径之一。星际无碰撞激波的Balmer发射线包括宽线和窄线两个明显的成分。通常认为,这种双线成分是与激波联系在一起的,宽线产生于激波前慢中性粒子与激波后高能质子的电荷交换,反映了激波后粒子的热运动状况,而窄线则产生于激波前慢中性粒子的激发,反映了激波前粒子的热运动状况。但是,近来更细致的观测和理论计算表明,超新星遗迹中Balmer发射线的双线结构很可能还要受到其他因素的影响,并且与激波速度和电子-质子的热平衡有着密切的关系。该文将讨论影响Balmer双线结构的各种因素,并讨论Balmer双线结构在超新星遗迹研究中的一些应用。

Bahner line is an important way for studying the interstellar collisionless shock. In the optical spectra of some young supernova remnants, Bahner line is often observed to have two components： a broad component produced by charge exchange between cold neutral atoms and high energy protons, and a narrow component produced mainly by collisional excitation of preshoek cold neutral atoms. Recently, more precise observations and theoretical calculations show that this kind of Bahner double line may be influenced by some other processes, and may be related to shock velocity and electron-proton equilibrium. In this paper, the physical processes which could influence Bahner double line and the use of Balmer double line in studying supernova remnants will be discussed. In section 2, we will first introduce the essential model of Balmer double-line only considering about collisional excitation of cold neutral atoms and charge exchange between cold neutral atoms and high energy protons. Then we will discuss other processes which will influence Bahner double line, including Lyman line trapping and different kinds of precursors. In section 3, the use of Bahner double line in studying supernova remnants will be discussed. Bahner double line can be used to determine the shock velocity and the angle between the shock propagating direction and the line of sight. It can also be used to determine the state of e-p equilibrium. The anti-correlation between shock velocity and the degree of e-p equilibrium is also discussed in section 3.4. This anti-correlation can be either intrinsic or due to the evolution of supernova remnants. Finally, in section 4, we will discuss some recent observations about the Bahner double line discovered in SN 1987A. Also we will briefly look into the future about the research in this field.