Rapid-response mode VLT/UVES spectroscopy of GRB 060418

Vreeswijk, P. M.; Ledoux, C.; Smette, A.; Ellison, Sara L.; Jaunsen, A. O.; Andersen, M. I.; Fruchter, A. S.; Fynbo, J. P. U.; Hjorth, J.; Kaufer, A.; Møller, P.; Petitjean, P.; Savaglio, S.; Wijers, R. A. M. J.

doi:10.1051/0004-6361:20066780

Cited by 179 publications

(261 citation statements)

References 56 publications

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“…Using the ratio between fine-structure and resonant abundances of the same element, one can determine a rough distance of the material from the GRB itself, assuming the levels are populated by indirect UV pumping from the GRB (see Prochaska et al 2006;Vreeswijk et al 2007). We compute the distance between the GRB and the absorbing systems using a Vreeswijk et al 2007 for details) predicting the ratio between fine structure and ground state levels.…”

Section: Kinematicsmentioning

confidence: 99%

“…We compute the distance between the GRB and the absorbing systems using a Vreeswijk et al 2007 for details) predicting the ratio between fine structure and ground state levels. We use as input the GRB flux, spectral and temporal indices estimated in this paper, a Doppler parameter of 12.6 km/s (see section 3.1), and we assume that the gas is completely in its ground states when the GRB explodes.…”

Section: Kinematicsmentioning

confidence: 99%

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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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Section: Kinematicsmentioning

confidence: 99%

Section: Kinematicsmentioning

confidence: 99%

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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“…Unlike intervening QSO absorbers and damped Lyman-α (DLA) systems (N(H 0 ) ≥ 10 20.3 atoms cm −2 ) observed in QSO spectra, strong absorption lines involving fine-structure and other metastable levels of ions such as O 0 , Si + , and Fe + are ubiquitous in GRB-DLAs (Vreeswijk et al 2004;Chen et al 2005;Berger et al 2006;Penprase et al 2006;Prochaska et al 2006Prochaska et al , 2007aD'Elia et al 2007;Vreeswijk et al 2007;Thöne et al 2008). These levels could be populated by collisions with electrons if the particle density per unit volume is high enough, by indirect excitation by IR photons, or by the UV flux from the GRB afterglow.…”

Section: Introductionmentioning

confidence: 99%

Physical conditions in high-redshift GRB-DLA absorbers observed with VLT/UVES: implications for molecular hydrogen searches

Ledoux¹,

Vreeswijk

Smette³

et al. 2009

A&A

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Aims. We aim to understand the nature of the absorbing neutral gas in the galaxies hosting high-redshift long-duration gamma-ray bursts (GRBs) and to determine their physical conditions. Methods. A detailed analysis of high-quality VLT/UVES spectra of the optical afterglow of GRB 050730 and other Swift-era bursts is presented. Results. We report the detection of a significant number of previously unidentified allowed transition lines of Fe + , involving the fine structure of the ground term ( 6 D 7/2 , 6 D 5/2 , 6 D 3/2 , 6 D 1/2 ) and that of other excited levels ( 4 F 9/2 , 4 F 7/2 , 4 F 5/2 , 4 F 3/2 , 4 D 7/2 , 4 D 5/2 ), from the z abs = 3.969, log N(H 0 ) = 22.10, damped Lyman-α (DLA) system located in the host galaxy of GRB 050730. No molecular hydrogen (H 2 ) is detected down to a molecular fraction of log f < −8.0. We derive accurate metal abundances for Fe + , S + , N 0 , Ni + , and, for the first time in this system, Si + and Ar 0 . The absorption lines are best-fit as a single narrow velocity component at z abs = 3.96857. The time-dependent evolution of the observed Fe + energy-level populations is modelled by assuming the excitation mechanism is fluorescence following excitation by ultraviolet photons emitted by the afterglow of GRB 050730. This UV pumping model successfully reproduces the observations, yielding a total Fe + column density of log N = 15.49 ± 0.03, a burst/cloud distance (defined to the near-side of the cloud) of d = 440 ± 30 pc, and a linear cloud size of l = 520 +240 −190 pc. This application of our photoexcitation code demonstrates that burst/DLA distances can be determined without strong constraints on absorption-line variability provided enough energy levels are detected. From the cloud size, we infer a particle density of n H ≈ 5−15 cm −3 . Conclusions.We discuss these results in the context of no detections of H 2 and C i lines (with log N(C 0 )/N(S + ) < −3) in a sample of seven z > 1.8 GRB host galaxies observed with VLT/UVES. We show that the lack of H 2 can be explained by the low metallicities, [X/H] < −1, low depletion factors, and, at most, moderate particle densities of the systems. This points to a picture where GRB-DLAs typically exhibiting very high H 0 column densities are diffuse metal-poor atomic clouds with high kinetic temperatures, T kin > ∼ 1000 K, and large physical extents, l > ∼ 100 pc. The properties of GRB-DLAs observed at high spectral resolution towards bright GRB afterglows differ markedly from the high metal and dust contents of GRB-DLAs observed at lower resolution. This difference likely results from the effect of a bias, against systems of high metallicity and/or close to the GRB, due to dust obscuration in the magnitudelimited GRB afterglow samples observed with high-resolution spectrographs.

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“…2006) and GRB 060418 (Vreeswijk et al 2007). These detections allow to constrain the distance of the neutral gas between 100 pc and 1.5 kpc.…”

Section: Ism and Stellar Environments Of Grbsmentioning

confidence: 88%

Probing the Interstellar Medium and Stellar Environments of Long-Duration GRBs

2007

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Abstract.We review the properties of the gas surrounding high-redshift gamma-ray bursts (GRBs) assessed through the analysis of damped Lyman-alpha systems (DLAs) identified in their afterglow spectra. These GRB-DLAs are characterized by large H I column densities with a median of N (H I) = 10 21. 7 cm −2 , no molecular gas signatures, metallicities ranging from 1/100 to nearly solar with a median exceeding 1/10 solar, and no anomalous abundance patterns. The detection of the atomic Mg lines and the time-variability of the fine-structure lines demonstrates that the majority of the neutral gas along the GRB sightlines is located between 50 pc and a few kpc from the GRB. This implies that this gas is presumably associated with the ambient interstellar medium of the host galaxy and that the derived properties from low-ionization lines do not directly constrain the local environment of the GRB progenitor. The highly ionized gas, traced by N V lines, which could result from a pre-existing H II region produced by the GRB progenitor and neighboring OB stars, appears on the other hand to be very local to the GRB at about 10 pc, yielding a snapshot of the medium's physical conditions at this radius.

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Rapid-response mode VLT/UVES spectroscopy of GRB 060418

Cited by 179 publications

References 56 publications

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

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

Physical conditions in high-redshift GRB-DLA absorbers observed with VLT/UVES: implications for molecular hydrogen searches

Probing the Interstellar Medium and Stellar Environments of Long-Duration GRBs

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