标题： 伽马射线暴余辉的吸收特性测量结果由BeppoSAX获得 显示英文标题

标题： The absorption properties of gamma-ray burst afterglows measured by BeppoSAX

摘要： 我们对利用BeppoSAX测量的6个伽马射线暴（GRB）余辉的X射线吸收特性进行了分析。在初始GRB触发后的8小时到20小时之间，单独的光谱可以用一个光子指数约为2的幂律来描述，吸收程度与银河系值略有相符。综合来看，数据在>99.999置信水平上与零吸收不一致。这些数据仅与柱密度分布随每个爆发方向的总银河系吸收变化的分布略有相符（chi^2=9.6，自由度为6）。数据与GRB发生在宿主星系中的宇宙学模型一致。通过同时拟合一个吸收固定为银河系值的幂律光谱模型以及所有6个余辉光谱的额外红移吸收，发现宿主天体内的最佳拟合平均吸收为（1.01 ^0.28_0.51）10^22原子cm^-2。这个值与从光学数据推断的GRB970508、GRB971214和GRB980329的宿主星系柱密度相容，支持GRB发生在其宿主星系中高度吸收的恒星形成区域的假说。 显示英文摘要

摘要： We present an analysis of the X-ray absorption properties of 6 gamma-ray burst (GRB) afterglows measured with BeppoSAX. Between 8 hrs and 20 hrs after the initial GRB trigger, individual spectra can be described by a power-law with a photon index of ~2 and absorption marginally consistent with the galactic value. Taken collectively, the data are inconsistent with zero absorption at the >99.999 confidence level. The data are only marginally consistent with a distribution of column densities varying as the total galactic absorption in the direction of each of the bursts (chi^2 =9.6 for 6 degrees of freedom). The data are consistent with cosmological models in which GRB occur within host galaxies. By simultaneously fitting a power-law spectral model with absorption fixed at the galactic value and additional, redshifted, absorption to all 6 afterglow spectra, the best-fit average absorption within the host objects is found to be (1.01 ^0.28_0.51) 10^22 atom cm^-2. This value is compatible with the host galaxy column densities inferred from optical data for GRB970508, GRB971214 and GRB980329, supporting the hypothesis that GRB occur within heavily absorbed star forming regions of their host galaxies.