A mean redshift of 2.8 for<i><b>Swift</b></i>gamma-ray bursts

Jakobsson, P.; Levan, A. J.; Fynbo, J. P. U.; Priddey, R.; Hjorth, J.; Tanvir, N. R.; Watson, Derrick G.; Jensen, B. L.; Sollerman, J.; Natarajan, Priyamvada; Gorosabel, J.; Cerón, J. M. Castro; Pedersen, Kim Steenstrup; Pursimo, T.; Arnadottir, Anna; Castro-Tirado, A. J.; Davis, CJ; Deeg, H. J.; Fiuza, DA; Mykolaitis, S; Sousa, S. G.

doi:10.1051/0004-6361:20054287

Cited by 262 publications

(247 citation statements)

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“…It is also expected that the mean log T 90 for the intermediate group should be much higher in the Swift database because of the different redshift distributions (Band 2006;Jakobsson et al 2006;Bagoly et al 2006). The mean value of the BATSE's intermediate subgroup is 0.64 (Horváth 1998), but here the value is between 1.02 and 1.64.…”

Section: Discussion Of the Resultsmentioning

confidence: 77%

A comparison of the gamma-ray bursts detected by BATSE and Swift

Huja¹,

Mészáros²,

Řípa³

2009

A&A

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Aims. The durations of 388 gamma-ray bursts detected by the Swift satellite, are analyzed statistically to search for subgroups. The results are then compared with results obtained earlier for data from the BATSE database. Methods. We apply the standard χ 2 test. Results. As for data in the BATSE database, short and long subgroups are also reliably identified in the Swift data. An intermediate subgroup is also seen in the Swift database.Conclusions. The analysis of the entire sample of 388 GRBs provides a support for the existence of three subgroups.

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Section: Discussion Of the Resultsmentioning

confidence: 77%

A comparison of the gamma-ray bursts detected by BATSE and Swift

Huja¹,

Mészáros²,

Řípa³

2009

A&A

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“…Several attempts have been made to determine the cosmic SFR using GRBs (see, e.g., Yüksel et al 2008;Kistler et al 2009) indicating a shallower decay towards higher redshift than derived by galaxy SF measurements. The redshift distribution of Swift GRBs at high redshifts can be well explained by a constant cosmic star-formation density from redshift 3.5 onwards (Jakobsson et al, 2006) 6 . This could be explained if GRBs preferentially select low-metallicity regions.…”

Section: Grb 100219a In the Context Of High Redshift Galaxy Abundancesmentioning

confidence: 89%

GRB 100219A with X-shooter – abundances in a galaxy at z =4.7

Thöne¹,

Fynbo²,

Goldoni³

et al. 2012

Monthly Notices of the Royal Astronomical Society

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Context. Abundances of galaxies at redshifts z > 4 are difficult to obtain from damped Ly α (DLA) systems in the sightlines of quasars (QSOs) due to the Ly α forest blanketing and the low number of high-redshift quasars detected. Gamma-ray bursts (GRBs) with their higher luminosity are well suited to study galaxies out to the formation of the first stars at z > 10. Its large wavelength coverage makes the X-shooter spectrograph an excellent tool to study the interstellar medium (ISM) of high redshift galaxies, in particular if the redshift is not known beforehand. Aims. We want to determine the properties of a GRB host at z = 4.66723 from absorption lines. This is one of the highest redshifts where a detailed analysis with medium-resolution data is possible. Furthermore, we determine the dust extinction using the spectral energy distribution from X-rays to near infrared. Finally, we put the results in context to other GRBs at z > 4 and properties of (high redshift) QSO absorbers. Methods. The velocity components of the resonant and fine-structure absorption lines are fitted with Voigt-profiles and the metallicity determined from S, Si, Fe and O. Si II* together with the energy released in the UV restframe as determined from GROND photometric data gives us the distance of the absorbing material from the GRB. The extinction is determined from the spectral slope using X-ray spectral information and the flux calibrated X-shooter spectrum, cross calibrated with photometric data from GROND. We also collect information on all GRB hosts with z > 4. Results. We measure a relatively high metallicity of [M/H] = −1.0 ± 0.1 from S, the distance of the material showing fine-structure lines is 0.3 to 1.0 kpc. The extinction is moderate with A V = 0.24 ± 0.06 mag. Low-and high ionization as well as fine-structure lines show a complicated kinematic structure probably pointing to a merger in progress. We detect one intervening system at z = 2.18. Conclusions. GRB-DLAs have a shallower evolution of metallicity with redshift than QSO absorbers and no evolution in their HI column density or ionization fraction. GRB hosts at high redshift seem to continue the trend of the metallicity-luminosity relation towards lower metallicities but the sample is still too small to draw a definite conclusion. While the detection of GRBs at z > 4 with current satellites is still difficult, they are very important for our understanding of the early epochs of star-and galaxy-formation in the Universe.

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“…Given the extra difficulty of identifying afterglows at higher redshifts, our finding is broadly consistent with these predictions. This is extremely encouraging for the prospects of future space missions optimised for finding high-redshift GRBs, and ultimately for using them to measure the history of star formation at very high redshifts 26 . Second, it is close to the redshift range during which the bulk of the cosmic reionization is thought to have taken place.…”

Section: It Is Thought That the First Generations Of Massive Stars Inmentioning

confidence: 91%

A γ-ray burst at a redshift of z ≈ 8.2

Tanvir

Fox

Levan

et al. 2009

Nature

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565

447

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It is thought that the first generations of massive stars in the Universe were an important, and quite possibly dominant 1 , source of the ultra-violet radiation that reionized the hydrogen gas in the intergalactic medium (IGM); a state in which it has remained to the present day. Measurements of cosmic microwave background anisotropies suggest that this phase-change largely took place 2 in the redshift range z=10.8 ±1.4, while observations of quasars and Lyman-α galaxies have shown that the process was essentially completed 3,4,5 by z≈6. However, the detailed history of reionization, and characteristics of the stars and proto-galaxies that drove it, remain unknown. Further progress in understanding requires direct observations of the sources of ultra-violet radiation in the era of reionization, and mapping the evolution of the neutral hydrogen (H I) fraction through time. The detection of galaxies at such redshifts is highly challenging, due to their intrinsic faintness and high luminosity distance, whilst bright quasars appear to be rare It has long been recognised that GRBs have the potential to be powerful probes of the early universe. Known to be the end product of rare massive stars 11 , GRBs and their afterglows can briefly outshine any other source in the universe, and would be theoretically detectable to z ~ 20 and beyond 12,13 . Their association with individual stars means that they serve as a signpost of star formation, even if their host galaxies are too 5 faint to detect directly. Equally important, precise determination of the hydrogen Lyman-α absorption profile can provide a measure of the neutral fraction of the IGM at the location of the burst 9,10,14,15 . With multiple GRBs at z > 7, and hence lines of sight through the IGM, we could thus trace the process of reionization from its early stages.However, until now the highest redshift GRBs (at z = 6. Ground-based optical observations in the r, i and z filters starting within a few minutes of the burst revealed no counterpart at these wavelengths (see Supplementary Information (SI)).The United Kingdom Infrared Telescope (UKIRT) in Hawaii responded to an automated request, and began observations in the K-band 21 minutes post burst. These images ( Figure 1) revealed a point source at the reported X-ray position, which we concluded was likely to be the afterglow of the GRB. We also initiated further nearinfrared (NIR) observations using the Gemini-North 8-m telescope, which started 75 min after the burst, and showed that the counterpart was only visible in filters redder than about 1.2 µm. In this range the afterglow was relatively bright and exhibited a shallow spectral slope F ν ∝ ν -0.26 , in contrast to the deep limit on any flux in the Y filter (0.97-1.07 µm). Later observations from Chile using the MPI/ESO 2.2m telescope, Gemini South and the Very Large Telescope (VLT) confirmed this finding. The nondetection in the Y-band implies a power-law spectral slope between Y and J steeper than. This is impossible for dust at any redshift, and is a tex...

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A mean redshift of 2.8 forSwiftgamma-ray bursts

Cited by 262 publications

References 50 publications

A comparison of the gamma-ray bursts detected by BATSE and Swift

A comparison of the gamma-ray bursts detected by BATSE and Swift

GRB 100219A with X-shooter – abundances in a galaxy at z =4.7

A γ-ray burst at a redshift of z ≈ 8.2

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