标题： 软X射线吸收过量在伽马射线暴余辉光谱中的吸收：湍流星系际介质的吸收 显示英文标题

标题： Soft X-ray absorption excess in gamma-ray burst afterglow spectra: Absorption by turbulent ISM

摘要： 三分之二的长时伽马射线暴（GRB）在软X射线吸收方面表现出超过银河系的过量吸收。 从紫外和光学光谱推断出的金属柱密度与从软X射线光谱得出的柱密度有时相差一个数量级，后者更高。 在GRB X射线余辉光谱中观察到的软X射线吸收过量的起源仍然是一个备受争议的问题，这导致了对热物质在GRB宿主星系内部和外部对我们的X射线余辉观测的影响的大量研究。 然而，迄今为止提出的所有模型要么只能解释我们观测中的一小部分（即红移z > 2），要么它们要求吸收物质中存在相当极端的条件。 在本文中，我们研究了由碰撞电离和湍流的星际介质（ISM）对GRB余辉的吸收。 我们发现，密集（每立方厘米3个）的碰撞电离ISM可以产生UV/光学和软X射线吸收柱密度相差10倍，然而对于这样的视线方向，UV/光学和软X射线吸收柱密度比GRB余辉光谱低2-3个数量级。 对于那些软X射线过量达到一个数量级的GRBs，这里考虑的湍流ISM的吸收贡献将减轻额外吸收组分（如GRB周边介质和星系际介质）所需的条件。 显示英文摘要

摘要： Two-thirds of long duration gamma-ray bursts (GRBs) show soft X-ray absorption in excess of the Milky Way. The column densities of metals inferred from UV and optical spectra differ from those derived from soft X-ray spectra, at times by an order of magnitude, with the latter being higher. The origin of the soft X-ray absorption excess observed in GRB X-ray afterglow spectra remains a heavily debated issue, which has resulted in numerous investigations on the effect of hot material both internal and external to the GRB host galaxy on our X-ray afterglow observations. Nevertheless, all models proposed so far have either only been able to account for a subset of our observations (i.e. at z > 2), or they have required fairly extreme conditions to be present within the absorbing material. In this paper, we investigate the absorption of the GRB afterglow by a collisionally ionised and turbulent interstellar medium (ISM). We find that a dense (3 per cubic centimeters) collisionally ionised ISM could produce UV/optical and soft X-ray absorbing column densities that differ by a factor of 10, however the UV/optical and soft X-ray absorbing column densities for such sightlines and are 2-3 orders of magnitude lower in comparison to the GRB afterglow spectra. For those GRBs with a larger soft X-ray excess of up to an order of magnitude, the contribution in absorption from a turbulent ISM as considered here would ease the required conditions of additional absorbing components, such as the GRB circumburst medium and intergalactic medium.