Sign on

SAO/NASA ADS Astronomy Abstract Service


· Find Similar Abstracts (with default settings below)
· Electronic Refereed Journal Article (HTML)
· Full Refereed Journal Article (PDF/Postscript)
· arXiv e-print (arXiv:0907.3449)
· On-line Data
· References in the article
· Citations to the Article (20) (Citation History)
· Refereed Citations to the Article
· SIMBAD Objects (81)
· Associated Articles
· Also-Read Articles (Reads History)
·
· Translate This Page
Title:
Low-resolution Spectroscopy of Gamma-ray Burst Optical Afterglows: Biases in the Swift Sample and Characterization of the Absorbers [ Erratum: 2010ApJS..186..485F ]
Authors:
Fynbo, J. P. U.; Jakobsson, P.; Prochaska, J. X.; Malesani, D.; Ledoux, C.; de Ugarte Postigo, A.; Nardini, M.; Vreeswijk, P. M.; Wiersema, K.; Hjorth, J.; Sollerman, J.; Chen, H.-W.; Thöne, C. C.; Björnsson, G.; Bloom, J. S.; Castro-Tirado, A. J.; Christensen, L.; De Cia, A.; Fruchter, A. S.; Gorosabel, J.; Graham, J. F.; Jaunsen, A. O.; Jensen, B. L.; Kann, D. A.; Kouveliotou, C.; Levan, A. J.; Maund, J.; Masetti, N.; Milvang-Jensen, B.; Palazzi, E.; Perley, D. A.; Pian, E.; Rol, E.; Schady, P.; Starling, R. L. C.; Tanvir, N. R.; Watson, D. J.; Xu, D.; Augusteijn, T.; Grundahl, F.; Telting, J.; Quirion, P.-O.
Affiliation:
AA(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ; Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, IS-107 Reykjavík, Iceland ), AB(Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, IS-107 Reykjavík, Iceland ), AC(Department of Astronomy and Astrophysics, UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064, USA ), AD(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ), AE(European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19, Chile ), AF(European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19, Chile ), AG(SISSA, Via Beirut 2/4, I-34014 Trieste, Italy ), AH(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ; European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19, Chile ), AI(Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK ), AJ(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ), AK(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ; Department of Astronomy, The Oskar Klein Centre, Stockholm University, 106 91 Stockholm, Sweden ), AL(Department of Astronomy & Astrophysics and Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA ), AM(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ; INAF, Osservatorio Astronomico di Brera, Via Bianchi 46 I-23806 Merate, Italy ), AN(Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, IS-107 Reykjavík, Iceland ), AO(Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA ), AP(IAA-CSIC, P.O. Box 03004, E-18080 Granada, Spain ), AQ(European Southern Observatory, Karl-Schwarzschildstrasse 2, D-85748 Garching, Germany ), AR(Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, IS-107 Reykjavík, Iceland ), AS(Space Telescope Science Institute, Department of Physics and Astronomy, Johns Hopkins University, 3700 San Martin Drive, Baltimore, MD 21218, USA ), AT(IAA-CSIC, P.O. Box 03004, E-18080 Granada, Spain ), AU(Space Telescope Science Institute, Department of Physics and Astronomy, Johns Hopkins University, 3700 San Martin Drive, Baltimore, MD 21218, USA ), AV(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ; Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo, Norway ), AW(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ), AX(Thüringer Landessternwarte Tautenburg, Sternwarte 5, D-07778 Tautenburg, Germany ), AY(NASA Marshall Space Flight Center, Huntsville, AL 35805, USA ), AZ(Department of Physics, University of Warwick, Coventry CV4 7AL, UK ), BA(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ), BB(INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy ), BC(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ), BD(INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy ), BE(Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA ), BF(INAF-Trieste Astronomical Observatory, 34143 Trieste, Italy ), BG(Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK ), BH(The UCL Mullard Space Science Laboratory, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK ), BI(Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK ), BJ(Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK ), BK(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ), BL(Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen Ø, Denmark ), BM(Nordic Optical Telescope Apartado 474, 38700 Santa Cruz de La Palma, Santa Cruz de Tenerife, Spain ), BN(Institute of Physics and Astronomy, University of Århus, Ny Munkegade, DK-8000 Århus C, Denmark), BO(Nordic Optical Telescope Apartado 474, 38700 Santa Cruz de La Palma, Santa Cruz de Tenerife, Spain ), BP(Institute of Physics and Astronomy, University of Århus, Ny Munkegade, DK-8000 Århus C, Denmark)
Publication:
The Astrophysical Journal Supplement, Volume 185, Issue 2, pp. 526-573 (2009). (ApJS Homepage)
Publication Date:
12/2009
Origin:
IOP
ApJ Keywords:
dust, extinction, galaxies: high-redshift, gamma rays: bursts
DOI:
10.1088/0067-0049/185/2/526
Bibliographic Code:
2009ApJS..185..526F

Abstract

We present a sample of 77 optical afterglows (OAs) of Swift detected gamma-ray bursts (GRBs) for which spectroscopic follow-up observations have been secured. Our first objective is to measure the redshifts of the bursts. For the majority (90%) of the afterglows, the redshifts have been determined from the spectra. We provide line lists and equivalent widths (EWs) for all detected lines redward of Lyα covered by the spectra. In addition to the GRB absorption systems, these lists include line strengths for a total of 33 intervening absorption systems. We discuss to what extent the current sample of Swift bursts with OA spectroscopy is a biased subsample of all Swift detected GRBs. For that purpose we define an X-ray-selected statistical sample of Swift bursts with optimal conditions for ground-based follow-up from the period 2005 March to 2008 September; 146 bursts fulfill our sample criteria. We derive the redshift distribution for the statistical (X-ray selected) sample and conclude that less than 18% of Swift bursts can be at z > 7. We compare the high-energy properties (e.g., γ-ray (15-350 keV) fluence and duration, X-ray flux, and excess absorption) for three subsamples of bursts in the statistical sample: (1) bursts with redshifts measured from OA spectroscopy; (2) bursts with detected optical and/or near-IR afterglow, but no afterglow-based redshift; and (3) bursts with no detection of the OA. The bursts in group (1) have slightly higher γ-ray fluences and higher X-ray fluxes and significantly less excess X-ray absorption than bursts in the other two groups. In addition, the fractions of dark bursts, defined as bursts with an optical to X-ray slope βOX < 0.5, is 14% in group (1), 38% in group (2), and >39% in group (3). For the full sample, the dark burst fraction is constrained to be in the range 25%-42%. From this we conclude that the sample of GRBs with OA spectroscopy is not representative for all Swift bursts, most likely due to a bias against the most dusty sight lines. This should be taken into account when determining, e.g., the redshift or metallicity distribution of GRBs and when using GRBs as a probe of star formation. Finally, we characterize GRB absorption systems as a class and compare them to QSO absorption systems, in particular the damped Lyα absorbers (DLAs). On average GRB absorbers are characterized by significantly stronger EWs for H I as well as for both low and high ionization metal lines than what is seen in intervening QSO absorbers. However, the distribution of line strengths is very broad and several GRB absorbers have lines with EWs well within the range spanned by QSO-DLAs. Based on the 33 z > 2 bursts in the sample, we place a 95% confidence upper limit of 7.5% on the mean escape fraction of ionizing photons from star-forming galaxies.

Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under programs 275.D-5022 (PI: Chincarini), 075.D-0270 (PI: Fynbo), 077.D-0661 (PI: Vreeswijk), 077.D-0805 (PI: Tagliaferri), 177.A-0591 (PI: Hjorth), 078.D-0416 (PI: Vreeswijk), 079.D-0429 (PI: Vreeswijk), 080.D-0526 (PI: Vreeswijk), 081.A-0135 (PI: Greiner), 281.D-5002 (PI: Della Valle), and 081.A-0856 (PI: Vreeswijk). Also based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Some of the data obtained herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck foundation.


Associated Articles

Main Paper     Erratum    


Bibtex entry for this abstract   Preferred format for this abstract (see Preferences)

   

Find Similar Abstracts:

Use: Authors
Title
Keywords (in text query field)
Abstract Text
Return: Query Results Return    items starting with number
Query Form
Database: Astronomy
Physics
arXiv e-prints