切仑科夫铁Kα和Kβ发射线的强度比和本征红移比的计算及其在活动星系核中的可能应用  

The Calculation of the Ratios of Intensities and the Intrinsic Redshifts of Cerenkov Iron Kα and Kβ Lines and Its Possible Application in the Researches Towards Active galactic Nuclei

作　　者：刘当波[1] 陈磊[2] 尤峻汉[1] 

机构地区：[1]上海交通大学物理系空间与天体物理研究所,上海200240 [2]中国科学院上海天文台,上海200030

出　　处：《天文学报》2007年第3期269-279,共11页Acta Astronomica Sinica

基　　金：国家自然科学基金(No.10373010;10778621);高校博士点科研基金(No.20030248012)资助项目

摘　　要：当具有各向同性速度分布的相对论电子穿过稠密气体区,或者轰击稠密气体区的表面时,切仑科夫效应将会产生一种特殊的原子或离子发射线,称做切仑科夫线状发射.这一预言在光学波段已由实验室的实验所证实.把线状发射理论推广到X射线波段,给出计算切仑科夫铁Kα和Kβ发射线的强度比和本征红移比的基本公式,列出了不同价次铁线的强度比和本征红移比.这一计算结果在活动星系核中有可能找到潜在的应用.最近观测发现源NGC3783,除存在着6.4 keV的铁Kα发射线,还存在着很强的7.0 keV的铁Kβ发射线,且两者等值宽度之比为EW_(Kα)/EW_(Kβ)≈3.43,这很难用传统的"光电吸收-莹光机制"来解释.切仑科夫线状发射机制可为解决这一困惑提供一条新途径.此外,期待切仑科夫铁Kα和Kβ线的本征红移比也会在以后的观测中能得到检验.假如切仑科夫线状辐射的设想得到观测的进一步支持,则对中央大质量黑洞周围物理环境的传统认识将有大的修改-活动更加剧烈,而且更加高能,其中气体也更加稠密.We mentioned that, when the thermal relativistic electrons with isotropic distribution of velocities move through a dense gas region, or impinge upon the surface of a cloud of dense gas, the Cerenkov effect will produce peculiar atomic or ionic emission lines, which we call the ＇Cerenkov line-like radiation＇. This prediction has been verified by the laboratory experiments in the optical waveband. In this paper, we present the basic formula for calculating the intensity ratio and the intrinsic redshift ratio of the Cerenkov iron Kα and Kβ lines. Using these formulae, we calculate the intensity ratios and the redshift ratios of the Cerenkov iron Kα and Kβ lines for different valences of iron ions, which can be examined by the observations of AGNs. The recent observations show that, except for the iron Kα line at ～ 6.4 keV, there is also an apparent iron Kβ line at ～ 7.0 keV in NGC 3783 with intensity markedly higher than the predicted one by the traditional fluorescence emission. We argue that, the Cerenkov line-like radiation can provide a way to solve the puzzle of the observed anomalous ratio of the equivalent widths EWKα/EWKβ≈3.43, which is difficult to understand from the conventional ＇photoelectric absorption-fluorescence emission＇ mechanism. Besides, we expected that the intrinsic redshift ratio of the Cerenkov iron Kα and Kβ lines could be verified in future observations. If our suggestion is further supported by observations, the conventional scenario around the central super massive black hole of AGNs would need to be modified to accommodate more energetic, more violent and much denser environment than previously thought.

关 键 词：辐射机制 通论 谱线:形成 X-射线 星系 星系赛弗特 类星体 普通 黑洞物理 

分 类 号：P158[天文地球—天文学]