The optical afterglow and host galaxy of GRB 000926 ^*,**,***

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

Corresponding author: J. U. Fynbo, jfynbo@eso.org

Received: 9 February 2001
Accepted: 6 April 2001

Abstract

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 . 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 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.).