Volume 523, November-December 2010
|Number of page(s)||21|
|Section||Interstellar and circumstellar matter|
|Published online||18 November 2010|
Photometry and spectroscopy of GRB 060526: a detailed study of the afterglow and host galaxy of a z = 3.2 gamma-ray burst⋆,⋆⋆
Dark Cosmology Centre, Niels Bohr Institute, University of
Copenhagen, Juliane Maries Vej
2 INAF – Osservatorio Astronomico di Brera, via Bianchi 46, 23807 Merate ( Lc), Italy
3 Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
4 Science Institute, University of Iceland, Dunhaga 3, 107 Reykjavík, Iceland
5 Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305, USA
6 Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
7 Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA
8 Physical Research Laboratory, Ahmedabad – 380 009, India
9 Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, 40127 Bologna, Italy
10 Kazan Federal University and Academy of Sciences of Tatarstan, Kazan, Russia
11 Department of Astronomy, 601 Campbell Hall, University of California, Berkeley, CA 94720–3411, USA
12 Space Research Institute (IKI), 84/32 Profsoyuznaya Str, Moscow 117997, Russia
13 Department of Astronomy, Yale University, PO Box 208101, New Haven, CT 06520, USA
14 Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
15 Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
16 UCD School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
17 Max-Planck-Institute for Extraterrestrial Physics, Giessenbachstraße, 85748 Garching, Germany
18 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD21218, USA
19 Ulugh Beg Astronomical Institute, 33 Astronomical Str., Tashkent 700052, Uzbekistan
20 INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Italy
21 Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavík, Iceland
22 Instituto de Astrofísica de Andalucía (IAA-CSIC), PO Box 3.004, 18. 080 Granada, Spain
23 Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
24 Centre for Star and Planet Formation, Geological Museum, Øster Voldgade 5-7, 1350 Copenhagen, Denmark
25 Tübitak National Observatory, Antalya, Turkey
26 Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA
27 Department of Physics, Univ. of Warwick, Coventry, CV4 7AL, UK
28 INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica di Bologna, via Gobetti 101, 40129 Bologna, Italy
29 University of Helsinki Observatory, PO Box 14 ( Tähtitorninmäki), 00014, Finland
30 VU Institute of Theoretical Physics and Astronomy, A. Gostauto 12, 01108 Vilnius, Lithuania
31 Space Science Department, Southwest Research Institute, San Antonio, TX 78238, USA
32 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
33 Crimean Astrophysical Observatory, Nauchny, Crimea, 98409, Ukraine
34 Physics Department, University of California at Santa Barbara, 2233B Broida Hall, Santa Barbara, CA 93106, USA
35 Tabasgo Fellow, USA
36 Max-Plank-Institut für Astrophysik, Karl-Schwarzschild Straße 1, 85741 Garching, Germany
37 Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
38 Second University of Roma “Tor Vergata”, Italy
39 Department of Astronomy, University of Texas at Austin, Austin TX, 78712, USA
40 Department of Physics, College of St. Benedict/St. Johns University, Collegeville, MN 56321, USA
Accepted: 17 July 2010
Aims. With this paper we want to investigate the highly variable afterglow light curve and environment of gamma-ray burst (GRB) 060526 at z = 3.221.
Methods. We present one of the largest photometric datasets ever obtained for a GRB afterglow, consisting of multi-color photometric data from the ultraviolet to the near infrared. The data set contains 412 data points in total to which we add additional data from the literature. Furthermore, we present low-resolution high signal-to-noise spectra of the afterglow. The afterglow light curve is modeled with both an analytical model using broken power law fits and with a broad-band numerical model which includes energy injections. The absorption lines detected in the spectra are used to derive column densities using a multi-ion single-component curve-of-growth analysis from which we derive the metallicity of the host of GRB 060526.
Results. The temporal behaviour of the afterglow follows a double broken power law with breaks at t = 0.090 ± 0.005 and t = 2.401 ± 0.061 days. It shows deviations from the smooth set of power laws that can be modeled by additional energy injections from the central engine, although some significant microvariability remains. The broadband spectral-energy distribution of the afterglow shows no significant extinction along the line of sight. The metallicity derived from S ii and Fe ii of [S/H] = –0.57 ± 0.25 and [Fe/H] = –1.09 ± 0.24 is relatively high for a galaxy at that redshift but comparable to the metallicity of other GRB hosts at similar redshifts. At the position of the afterglow, no host is detected to F775W(AB) = 28.5 mag with the HST, implying an absolute magnitude of the host M(1500 Å) > –18.3 mag which is fainter than most long-duration hosts, although the GRB may be associated with a faint galaxy at a distance of 11 kpc.
Key words: gamma rays bursts: individual: GRB 060526 / galaxies: high-redshift / ISM: abundances
Based in part on observations obtained with the European Southern Observatory’s Very Large Telescope under proposals 077.D-0661 (PI: Vreeswijk) and 177.A-0591 (PI: Hjorth), as well as observations obtained with the NASA/ESA Hubble Space Telescope under proposal 11734 (PI: Levan).
Table 1 is only available in electronic form at http://www.aanda.org
© ESO, 2010
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