Based on observations taken at the INT and NOT telescopes, operated on the island of La Palma by the ING and NOT teams in the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofísica de Canarias.

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Figure 1 is only available in electronic form at
http://www.edpsciences.org

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... STSDAS

IRAF is the Image Analysis and Reduction Facility made available to the astronomical community by the National Optical Astronomy Observatories, which are operated by AURA, Inc., under contract with the U.S. National Science Foundation. STSDAS is distributed by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555.

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