Salvaterra 2009 高红移伽玛暴GRB 090423的观测

主要内容:
红移为8.1, 意味着发生在再电离还没结束的时候(而再电离之前的时期, 即中性氢时代被成为dark age, 再电离之后就没有再复合了, 今天的宇宙是处于完全电离态的(from here)。).

什么意思啊? 是电离度上升还没结束? 还是复合回到中性还没结束? 不过从这里看, 应该是前者. "the first sources of light began to form at a redshift z = 30 and reionized most of the hydrogen in the universe by z = 7."

这个暴的观测, 应该还加上其它几个高红移暴, 说明早期宇宙的伽玛暴诞生率比现在高. 那么要么是伽玛暴和恒星形成率不成比例, 要么是早期恒星形成率高.

精彩摘抄:

From pictures

和别的伽玛暴比较, 没有什么特别的

From pictures

红移得到的方式

From pictures

满足Amati关系

From pictures

X射线和光学的光变曲线

文章信息:

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Title:		GRB 090423 reveals an exploding star at the epoch of re-ionization
Authors:		Salvaterra, R.; Della Valle, M.; Campana, S.; Chincarini, G.; Covino, S.; D'Avanzo, P.; Fernandez-Soto, A.; Guidorzi, C.; Mannucci, F.; Margutti, R.; Thoene, C. C.; Antonelli, L. A.; Barthelmy, S. D.; De Pasquale, M.; D'Elia, V.; Fiore, F.; Fugazza, D.; Hunt, L. K.; Maiorano, E.; Marinoni, S.; Marshall, F. E.; Molinari, E.; Nousek, J.; Pian, E.; Racusin, J. L.; Stella, L.; Amati, L.; Andreuzzi, G.; Cusumano, G.; Fenimore, E. E.; Ferrero, P.; Giommi, P.; Guetta, D.; Holland, S. T.; Hurley, K.; Israel, G. L.; Mao, J.; Markwardt, C. B.; Masetti, N.; Pagani, C.; Palazzi, E.; Palmer, D. M.; Piranomonte, S.; Tagliaferri, G.; Testa, V.
Publication:		eprint arXiv:0906.1578
Publication Date:		06/2009
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Comment:		Submitted to Nature. The astro-ph paper includes the main text (8 pages, 2 figures) and supplementary material (13 pages, 6 figures). Please note that this manuscript is subject to press embargo
Bibliographic Code:		2009arXiv0906.1578S

Abstract

The observation of the very early stages of the Universe represents one of the main challenges of modern cosmology. 200-300 million years after the Big Bang stars began to form, thus providing the Universe with the first sources of light and heat after the Big Bang. This event marks the transition between the epoch when the Universe was dark and neutral and the time when the Universe became fully ionized. The direct investigation of this cosmic epoch, usually accomplished by observing distant quasars, has been revolutionized in the last decade through the study of Gamma-ray Bursts (GRBs). GRBs are gamma-ray flashes, detected from space, produced by rare types of massive stellar explosions. Their rapidly fading afterglows are often bright at optical wavelengths, such that GRBs are detectable up to cosmological distances. Here we report on the Swift observation of GRB 090423 and the near-infrared spectroscopic measurement of its redshift z=8.1^{+0.1}_{-0.3} obtained with the Telescopio Nazionale Galileo (TNG). This GRB was produced in a cosmic explosion that occurred before the re-ionization process was completed, when the Universe was only ~4% of its current age. Unexpectedly, this primordial object exhibits properties similar to those of GRBs observed at low/intermediate redshifts, indicating that the mechanisms and progenitors which gave rise to GRBs about 600 million years after the Big Bang are not markedly different from those producing GRBs ~10 billion years later. The detection of this GRB at z=8.1 indicates either that the GRBs are not good tracers of the cosmic star formation or that the number of bright GRBs was greater at high redshift.

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