主要内容:
说明伽玛暴周围缺少氢分子，文章分析发现单个伽玛暴的前身星就可以电离周围的中性氢。
精彩摘抄:
文章信息:
- · arXiv e-print (arXiv:0802.0737)
- · References in the Article
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| Title: |
| The Molecular Hydrogen Deficit in Gamma-Ray Burst Afterglows |
| Authors: |
| Whalen, Daniel; Prochaska, Jason X.; Heger, Alexander; Tumlinson, Jason |
| Publication: |
| eprint arXiv:0802.0737 |
| Publication Date: |
| 02/2008 |
| Origin: |
| ARXIV |
| Keywords: |
| Astrophysics |
| Comment: |
| 10 pages, 9 figures, submitted to ApJ |
| Bibliographic Code: |
| 2008arXiv0802.0737W |
Abstract
Recent analysis of five gamma-ray burst (GRB) afterglow spectra reveal the absence of molecular hydrogen absorption lines, a surprising result in light of their large neutral hydrogen column densities and the detection of H$_2$ in similar, more local star-forming regions like 30 Doradus in the LMC. Observational evidence further indicates that the bulk of the neutral hydrogen column in these sight lines lies 100 pc beyond the progenitor and that H$_2$ was absent prior to the burst, suggesting that direct flux from the star, FUV background fields, or both suppressed its formation. We present one-dimensional radiation hydrodynamical models of GRB host galaxy environments, including self-consistent radiative transfer of both ionizing and Lyman-Werner photons, nine-species primordial chemistry with dust formation of H$_2$, and dust extinction of UV photons. We find that a single GRB progenitor is sufficient to ionize neutral hydrogen to distances of 50 - 150 pc but that a galactic Lyman-Werner background is required to dissociate the molecular hydrogen. Only modest intensities of 0.01 - 8 times the Galactic mean are necessary to destroy H$_2$ in the cloud, depending on its density and metallicity. The minimum radii at which neutral hydrogen will be found in afterglow spectra is insensitive to the mass of the progenitor or the initial mass function (IMF) of its cluster, if present.
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