arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1007.5357astro-ph.HE
收藏

GRB 090926 A余辉的VLT/X-射手光谱

VLT/X-shooter spectroscopy of the GRB 090926A afterglow

V. D'Elia, J. P. U. Fynbo, S. Covino, P. Goldoni, P. Jakobsson, F. Matteucci, S. Piranomonte, J. Sollerman, C. C. Thoene, S. D. Vergani, P. M. Vreeswijk, D. J. … 展开作者

V. D'Elia, J. P. U. Fynbo, S. Covino, P. Goldoni, P. Jakobsson, F. Matteucci, S. Piranomonte, J. Sollerman, C. C. Thoene, S. D. Vergani, P. M. Vreeswijk, D. J. Watson, K. Wiersema, T. Zafar, A. de Ugarte Postigo, H. Flores, J. Hjorth, L. Kaper, A. J. Levan, D. Malesani, B. Milvang-Jensen, E. Pian, G. Tagliaferri, N. R. Tanvir

摘要:

通过对伽马射线暴GRB 090926 A余辉光谱的分析,研究了该暴的环境和干扰吸收体。我们分析了伽玛暴090926 A的中分辨率光谱观测(R= 10000,对应于30 km/s,S/N=15 - 30,波长范围3000-25000),在伽玛暴触发后~ 22小时的VLT上用X射线摄影机拍摄。光谱表明,在伽玛暴宿主星系在z = 2.1071的ISM是丰富的吸收功能,有两个组件有助于线的轮廓。除了基态谱线外,我们还探测到了C Ⅱ、O Ⅰ、Si Ⅱ、Fe Ⅱ和Ni Ⅱ的激发吸收特征。没有主机星系发射线,分子吸收功能,也没有弥漫的星际带中检测到的光谱。GRB 090926 A的氢柱密度为log N_H/cm^{-2} = 21.60 +/- 0.07,主星系的金属丰度相对于太阳值在[X/H] = 3.2 × 10 ^{-3}-1.2 × 10 ^{-2}的范围内,即,是伽玛射线暴宿主星系观测到的最低值之一。与星系化学演化模型的比较表明,GRB 090926 A的宿主可能是一个矮不规则星系。我们对主星系ISM的氢分子分数设定了一个上限,即f <7 X10 ^{-7}。我们得到的信息之间的距离主机吸收气体和伽玛射线暴爆炸的网站。发现分量I的距离为2.40 +/- 0.15 kpc,而分量II位于远离GRB的位置,可能在~ 5 kpc处。这些值与其他伽玛暴的值是一致的。

英文摘要:

The aim of this paper is to study the environment and intervening absorbers of the gamma-ray burst GRB 090926A through analysis of optical spectra of its afterglow. We analyze medium resolution spectroscopic observations (R=10 000, corresponding to 30 km/s, S/N=15 - 30 and wavelength range 3000-25000) of the optical afterglow of GRB 090926A, taken with X-shooter at the VLT ~ 22 hr after the GRB trigger. The spectrum shows that the ISM in the GRB host galaxy at z = 2.1071 is rich in absorption features, with two components contributing to the line profiles. In addition to the ground state lines, we detect C II, O I, Si II, Fe II and Ni II excited absorption features. No host galaxy emission lines, molecular absorption features nor diffuse interstellar bands are detected in the spectrum. The Hydrogen column density associated to GRB 090926A is log N_H/cm^{-2} = 21.60 +/- 0.07, and the metallicity of the host galaxy is in the range [X/H] =3.2X10^{-3}-1.2X10^{-2} with respect to the solar values, i.e., among the lowest values ever observed for a GRB host galaxy. A comparison with galactic chemical evolution models has suggested that the host of GRB090926A is likely to be a dwarf irregular galaxy. We put an upper limit to the Hydrogen molecular fraction of the host galaxy ISM, which is f < 7X10^{-7}. We derive information on the distance between the host absorbing gas and the site of the GRB explosion. The distance of component I is found to be 2.40 +/- 0.15 kpc, while component II is located far away from the GRB, possibly at ~ 5 kpc. These values are compatible with that found for other GRBs.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑