Tables 1 to 5 and Figs. 1 to 13 and Sect. 4 are only available in electronic form at http://www.edpsciences.org

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Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under Cooperative Agreement no. NCC 5-538 with the National Aeronautics and Space Administration, Science Mission Directorate, Planetary Astronomy Program.

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...(Cushing et al. 2004)

SPEXTOOL is available from the IRTF web site at http://irtf.ifa.hawaii.edu/Facility/spex/spex.html

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