Strategies for prompt searches for GRB afterglows: The discovery of the GRB 001011 optical/near-infrared counterpart using colour-colour selection ^*

¹ Danish Space Research Institute, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
² European Southern Observatory, Karl–Schwarzschild–Straße 2, 85748 Garching, Germany e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
³ Astronomical Observatory, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
⁴ Observatoire Midi-Pyrénées (LAS), 14 avenue E. Belin, 31400 Toulouse, France
⁵ Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
⁶ Division of Astronomy, PO Box 3000, 90014 University of Oulu, Finland e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
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⁸ Laboratoire d'Astronomie Spatiale, Traverse du Siphon, BP 8, 13376 Marseille, France e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
⁹ Department of Astronomy, University of Toronto, 60 St. George Street, Toronto, ON, M5S 3H8, Canada e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
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¹² Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
¹³ Astrophysikalisches Institut, Potsdam, Germany e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
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¹⁶ Istituto Tecnologie e Studio Radiazioni Extraterrestri, CNR, via Gobetti 101, 40129 Bologna, Italy e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.
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¹⁸ NASA MSFC, SD-50, Huntsville, AL 35812, USA e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
¹⁹ Department of Physical Sciences, University of Hertfordshire, College Lane, Hatfield, Herts AL10 9AB, UK e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.
²⁰ Department of Physics and Astronomy, State University of New York, Stony Brook, NY 11794-3800, USA e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

Corresponding author: J. Gorosabel, This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 19 September 2001
Accepted: 8 November 2001

Abstract

We report the discovery of the optical and near-infrared counterparts to GRB 001011. The GRB 001011 error box determined by Beppo-SAX was simultaneously imaged in the near-infrared by the 3.58-m New Technology Telescope and in the optical by the 1.54-m Danish Telescope ~8 hr after the gamma-ray event. Here we implement the colour-colour discrimination technique proposed by Rhoads ([CITE]) and extend it using near-IR data as well. We present the results provided by an automatic colour-colour discrimination pipe-line developed to discern the different populations of objects present in the GRB 001011 error box. Our software revealed three candidates based on single-epoch images. Second-epoch observations carried out ~3.2 days after the burst revealed that the most likely candidate had faded, thus identifying it with the counterpart to the GRB. In deep R-band images obtained 7 months after the burst a faint () elongated object, presumably the host galaxy of GRB 001011, was detected at the position of the afterglow. The GRB 001011 afterglow is the first discovered with the assistance of colour-colour diagram techniques. We discuss the advantages of using this method and its application to error boxes determined by future missions.