EDP Sciences
Free access
Volume 373, Number 3, July III 2001
Page(s) 796 - 804
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20010531

A&A 373, 796-804 (2001)
DOI: 10.1051/0004-6361:20010531

The optical afterglow and host galaxy of GRB 000926

J. U. Fynbo1, J. Gorosabel2, T. H. Dall3, 4, J. Hjorth5, H. Pedersen5, M. I. Andersen6, P. Møller1, S. Holland7, I. Smail8, N. Kobayashi9, E. Rol10, P. Vreeswijk10, I. Burud11, B. L. Jensen5, B. Thomsen4, A. Henden12, F. Vrba12, B. Canzian12, J. M. Castro Cerón13, A. J. Castro-Tirado14, 15, T. Cline16, M. Goto10, J. Greiner17, M. T. Hanski18, K. Hurley19, N. Lund2, T. Pursimo18, R. Østensen20, J. Solheim20, N. Tanvir21 and H. Terada22

1  European Southern Observatory Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
2  Danish Space Research Institute, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
3  Nordic Optical Telescope, Apartado Postal 474, 38700 Santa Cruz de La Palma, Spain
4  Institute of Physics and Astronomy, University of Århus, 8000 Århus C, Denmark
5  Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
6  Division of Astronomy, PO Box 3000, 90014 University of Oulu, Finland
7  Department of Physics, University of Notre Dame, Notre Dame, IN 46556-5670, USA
8  Department of Physics, University of Durham, South Road, Durham DH1 3LE, UK
9  SUBARU Telescope, National Astronomical Observatory of Japan, 650 North A'ohoku Place Hilo, Hawaii 96720, USA
10  University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
11  Institut d'Astrophysique et de Géophysique, Université de Liège, Avenue de Cointe 5, 4000 Liège, Belgium
12  Universities Space Research Association U.S. Naval Observatory, Flagstaff Station, Flagstaff, AZ 86002-1149, USA
13  Real Instituto y Observatorio de la Armada, Sección de Astronomía, 11110 San Fernando-Naval, Cádiz, Spain
14  Instituto de Astrofísica de Andalucía (IAA-CSIC), PO Box 03004, 18080 Granada, Spain
15  Laboratorio de Astrofísica Espacial y Física Fundamental (LAEFF-INTA), PO Box 50727, 28080, Madrid, Spain
16  NASA Goddard Space Flight Center, Code 661, Greenbelt, MD 20771, USA
17  Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
18  Tuorla Observatory, University of Turku, 21500 Piikkiö, Finland
19  University of California, Berkeley, Space Sciences Laboratory, Berkeley, CA 94720-7450, USA
20  Department of Physics, University of Tromsø, Tromsø, Norway
21  Department of Physical Sciences, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB, UK
22  Department of Physics, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo, Kyoto 606-8502, Japan

(Received 9 February 2001 / Accepted 6 April 2001 )

We present the discovery of the Optical Transient (OT) of the long-duration gamma-ray burst GRB 000926. The optical transient was detected independently with the Nordic Optical Telescope and at Calar Alto 22.2 hours after the burst. At this time the magnitude of the transient was R = 19.36. The transient faded with a decay slope of about 1.7 during the first two days after which the slope increased abruptly (within a few hours) to about 2.4. The light-curve started to flatten off after about a week indicating the presence of an underlying extended object. This object was detected in a deep image obtained one month after the GRB at $R=23.87\pm0.15$ and consists of several compact knots within about 5 arcsec. One of the knots is spatially coincident with the position of the OT and hence most likely belongs to the host galaxy. Higher resolution imaging is needed to resolve whether all the compact knots belong to the host galaxy or to several independent objects. In a separate paper we present a discussion of the optical spectrum of the OT, and its inferred redshift (Møller et al., in prep.).

Key words: cosmology: observations -- gamma rays: bursts

Offprint request: J. U. Fynbo, jfynbo@eso.org

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