Patel, M. 2010 利用GRB 080913来分析星系际物质的电离率

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Title:		The reanalysis of spectra of GRB 080913 to estimate the neutral fraction of the IGM at a redshift of 6.7
Authors:		Patel, M.; Warren, S. J.; Mortlock, D. J.; Fynbo, J. P. U.
Affiliation:		AA(Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London, SW7 2AZ, UK m.patel06@imperial.ac.uk), AB(Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London, SW7 2AZ, UK), AC(Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London, SW7 2AZ, UK), AD(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 21000 Copenhagen, Denmark)
Publication:		Astronomy and Astrophysics, Volume 512, id.L3 (A&A Homepage)
Publication Date:		03/2010
Origin:		EDP Sciences
Keywords:		dark ages, reionization, first stars, gamma-ray burst: individual: GRB 080913, techniques: spectroscopic
DOI:		10.1051/0004-6361/200913876
Bibliographic Code:		2010A&A...512L...3P

Abstract

Aims: We reanalyse optical spectra of the z=6.7 gamma-ray burst GRB 080913, adding hitherto unpublished spectra, to reassess the measurement of the neutral fraction of the IGM at high redshifts.
Methods: In the data reduction, we take particular care to minimise systematic errors in the sky subtraction, which are evident in the published spectrum, and compromise our analysis. The final combined spectrum has a higher signal-to-noise ration (S/N) than the previously published spectrum by a factor of 1.3.
Results: We find a single significant absorption line redward of the Lyα continuum break, which we identify with the ii + Siii λ 0.126 μm blend, at z=6.733. The sharp spectral break at Lyα implies a comparatively low total column density of neutral hydrogen along the line of sight, log({N_HI}/cm^-2)<20. We model the absorption with a host-galaxy DLA, surrounded by an ionised region of unknown size r, within the IGM of neutral fraction, x_HI. Despite knowing the source redshift, and the improved S/N of the spectrum, when fitting only over wavelengths redward of Lyα, no useful constraints on x_HI can be obtained. We consider the possibility of including the ionised region, blueward of Lyα, when constraining the fit. For the optimistic assumption that the ionised region is transparent, τ_GP≪1, we find that the region is of small size r<2 proper Mpc, and we obtain an upper limit to the neutral fraction of the IGM at z=6.7 of x_HI<0.73 at a probability of 90%.

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Liu Xue-Wen 2009 磁能注入解释GRB 080913的余辉

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Title:		Magnetic Energy Injection in GRB 080913
Authors:		Xue-Wen, Liu; Xue-Feng, Wu; Tan, Lu
Publication:		eprint arXiv:0907.1767
Publication Date:		07/2009
Origin:		ARXIV
Keywords:		Astrophysics - Cosmology and Extragalactic Astrophysics, Astrophysics - High Energy Astrophysical Phenomena
Comment:		3 pages, pdf only. accepted for publication in Science in China Series G
Bibliographic Code:		2009arXiv0907.1767X

Abstract

GRB 080913, with a spectroscopically determined redshift of z=6.7, was the record holder of the remotest stellar object before the discovery of the recent gamma-ray burst GRB 090423, whose redshift is about 8.2. The gradually accumulated high redshift GRB sample has shed light on the origin and physics of GRBs during the cosmic re-ionization epoch. We here present a detailed numerical fit to the multi-wavelength data of the optical afterglow of GRB 080913 and then constrain its circum-burst environment and the other model parameters. We conclude that the late optical/X-ray plateau at about one day since the burst is due to the Poynting-flux dominated injection from the central engine which is very likely a massive spinning black hole with super strong magnetic fields.

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Zhang 2009 GRB 080913的观测以及Type I/II的分类

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再次强调他的根据是否有超新星成分等来分类Type I/II

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Title:		Physical classification scheme of cosmological Gamma-ray bursts and their observational characteristics: on the nature of z=6.7 GRB 080913 and some short/hard GRBs
Authors:		Zhang, Bing; Zhang, Bin-Bin; Virgili, Francisco J.; Liang, En-Wei; Kann, D. Alexander; Wu, Xue-Feng; Proga, Daniel; Lv, Hou-Jun; Toma, Kenji; Meszaros, Peter; Burrows, David N.; Roming, Peter W. A.; Gehrels, Neil
Publication:		eprint arXiv:0902.2419
Publication Date:		02/2009
Origin:		ARXIV
Keywords:		Astrophysics - High Energy Astrophysical Phenomena
Comment:		29 pages, submitted to ApJ
Bibliographic Code:		2009arXiv0902.2419Z

Abstract

(Abridged) The highest redshift (z=6.7) gamma-ray burst (GRB) 080913 recently detected by Swift is an intrinsically short, hard GRB. It would be recognized by BATSE as a short/hard GRB should it have occurred at z \leq 1. We perform a more thorough investigation on the physical classification scheme of cosmological GRBs and their observational characteristics. We reiterate the physical definitions of Type I/II GRBs and then review the observational criteria and their physical motivations. Contrary to the traditional approach of assigning the physical category based on the gamma-ray properties (duration, hardness, and spectral lag), we take the opposite approach to define the Type I and Type II Gold Samples using several criteria that are more directly related to the GRB progenitors and study the properties of the two Gold Samples and compare them with the traditional long/soft and short/hard samples. We find that the Type II Gold Sample reasonably tracks the long/soft population, although it includes several intrinsically short (shorter than 1s in the rest frame) GRBs. The Type I Gold Sample only has 5 GRBs, 4 of which are not strictly short but have extended emission. Other short/hard GRBs detected in the Swift era represent the BATSE short/hard sample well, but it is unclear whether all of them belong to Type I. We suspect that some high-luminosity short/hard GRBs may instead belong to Type II. We suggest that GRB 080913 is more likely a Type II event, although a Type I origin invoking a BH-NS merger is not ruled out. We re-emphasize the importance of invoking multiple observational criteria, and cautiously propose an operational procedure to determine the physical category of a particular GRB, with all the caveats laid out.

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Belczynski 2008 高红移暴GRB 080913的观测

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目前红移最高: z=6.7.
但前身星依然更可能是PopII而不是PopIII的. (也就是到目前为止还是没有popIII的前身星)

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Title:		On The Origin Of The Highest Redshift Gamma-Ray Burst GRB 080913
Authors:		Belczynski, Krzysztof; Hartmann, Dieter H.; Fryer, Chris L.; Holz, Daniel E.; O'Shea, Brian
Publication:		eprint arXiv:0812.2470
Publication Date:		12/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		13 pages, 5 figures, submitted to ApJ
Bibliographic Code:		2008arXiv0812.2470B

Abstract

GRB 080913, discovered by SWIFT, is the most distant gamma-ray burst (GRB) known to-date, with a spectroscopically determined redshift of z=6.7. The detection of a burst at such an early epoch of the Universe significantly constrains the nature of GRBs and their progenitors. To evaluate these constraints, we perform population synthesis studies of the formation and evolution of early stars and calculate the resulting formation rates of short- and long-duration GRBs at high redshift. The peak of the GRB rate from Population II stars occurs at z=7 for a model with efficient/fast mixing of metals, while it is found at z=3 for an inefficient/slow metallicity evolution model. We show that for at z=6.7 essentially all GRBs originate from Population II stars, independent of the adopted metallicity evolution model. At this epoch Population III (metal free) stars, representing the very first generation of stars, most likely have already completed their evolution, and Population I stars (representing the present population) have just begun forming. We argue that Population II stars (having small, but non-zero metallicity) are the most likely progenitors of both long GRBs (collapsars) and short GRBs (NS-NS or BH-NS mergers) in the redshift range 6\less z \less 10.> Bibtex entry for this abstract Preferred format for this abstract (see Preferences)

Greiner 2008 GRB 080913 observations

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Title:		GRB 080913 at redshift 6.7
Authors:		Greiner, J.; Kruehler, T.; Fynbo, J. P. U.; Rossi, A.; Schwarz, R.; Klose, S.; Savaglio, S.; Tanvir, N. R.; McBreen, S.; Totani, T.; Zhang, B. B.; Wu, X. F.; Watson, D.; Barthelmy, S. D.; Beardmore, A. P.; Ferrero, P.; Gehrels, N.; Kann, D. A.; Kawai, N.; Kuepcue Yoldas, A.; Meszaros, P.; Milvang-Jensen, B.; Oates, S. R.; Pierini, D.; Schady, P.; Toma, K.; Vreeswijk, P. M.; Yoldas, A.; Zhang, B.; Afonso, P.; Aoki, K.; Burrows, D. N.; Clemens, C.; Filgas, R.; Haiman, Z.; Hartmann, D. H.; Hasinger, G.; Hjorth, J.; Jehin, E.; Levan, A. J.; Liang, E. W.; Malesani, D.; Pyo, T. -S.; Schulze, S.; Szokoly, G.; Terada, H.; Wiersema, K.
Publication:		eprint arXiv:0810.2314
Publication Date:		10/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		14 pages, 7 figures, ApJ (subm)
Bibliographic Code:		2008arXiv0810.2314G

Abstract

We report on the detection by Swift of GRB 080913, and subsequent optical/near-infrared follow-up observations by GROND which led to the discovery of its optical/NIR afterglow and the recognition of its high-z nature via the detection of a spectral break between the i' and z' bands. Spectroscopy obtained at the ESO-VLT revealed a continuum extending down to lambda = 9400 A, and zero flux for 7500 A < z="6.695+-0.025">

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Perez-Ramirez 2008 high-z GRB 080913 observation

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Title:		Detection of the ultra-high z short GRB 080913 and its implications on progenitors and energy extraction mechanisms
Authors:		Perez-Ramirez, D.; de Ugarte Postigo, A.; Gorosabel, J.; Aloy, M. A.; Guerrero, M. A.; Osborne, J. P.; Page, K. L.; Warwick, R. S.; Horvath, I.; Veres, P.; Jelinek, M.; Kubanek, P.; Guziy, S.; Bremer, M.; Winters, J. M.; Castro-Tirado, A. J.
Publication:		eprint arXiv:0810.2107
Publication Date:		10/2008
Origin:		ARXIV
Keywords:		Astrophysics
Comment:		Letter to the Editor. 4 pages, 4 figures. Submitted to A&A
Bibliographic Code:		2008arXiv0810.2107P

Abstract

Aims: We present multiwavelength observations of the most distant (z~6.7) gamma-ray burst detected so far (GRB 080913) and study whether it can be considered a short- or an intermediate-duration GRB and the implications for the progenitor nature and energy extraction mechanisms. Methods: Multiwavelength (X-ray/nIR/millimetre) observations were taken between 20.7 hours and ~4.5 days after the event. Results: A very faint afterglow is barely seen at the 3.5m CAHA telescope in the nIR, being clearly detected on our XMM-Newton observations. An upper limit is reported in the mm range. GRB 080913 is located in the locus of short-duration GRBs on a hardness-duration diagram, thus strengthening its membership in this class. We also report that GRB 080913 shows lower isotropic luminosities than GRB 060121, another likely member of the class at z~4.6. Regarding the nature of the progenitor, we find that a NS+BH is slightly preferred over a double NS merger, with the Blandford-Znajek process operating in this subclass of extremely energetic short GRBs.

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