Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Programmes 67.D-0134 and 68.D-0114). Also based in part on observations with the NASA/ESA Hubble Space Telescope. These HST observations are associated with proposals GO-8602 and GO-9114.

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Tables 1, 2, 4 and 5 are only available in electronic form at http://www.edpsciences.org

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... instruments

http://www.eso.org/instruments/fors1/

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... software

IRAF, http://iraf.noao.edu/iraf/web/, is distributed by NOAO.

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... ESO

www.eso.org/observing/dfo/quality/FORS2/qc/photcoeff/photcoeffs_fors2.html

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... (ISAAC)

http://www.eso.org/instruments/isaac/

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... Eclipse

http://www.eso.org/projects/aot/eclipse/

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... respectively

http://www.eso.org/instruments/isaac/imaging_standards.html

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...2000)

Li et al. (2002) report R = 22.10 mag from an approximation, but the more detailed calculation for these transformations gives R=22.14 mag.

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... constrained

The distance measurements to NGC 524 are actually quite disaccording. Surface Brightness Fluctuation measurements indicate a distance modulus of $31.84\pm0.20$ , while a supernova estimate gives $32.53\pm0.35$ .

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...1996)

The peak luminosity of SN 2000cx from Candia et al. (2003), log (L/erg s^-1) $\approx$ 43.05, corresponds according to Contardo et al. (2000) to $\sim$ 0.56 $M_{\odot }$ , but Contardo et al. also did not include the UV part of the spectrum. The actual nickel mass of course depends crucially on the assumed distance, which is rather uncertain; we adopt 31.2 Mpc.

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