Mass–luminosity relations L(M) for the most massive stars in the Arches cluster, for an adopted metallicity of Z = 2Z_⊙. To investigate the influence of systematic uncertainties on our results, the observed luminosities have been artificially increased by 0.15 dex. To derive wind masses, the mass-loss rates have been increased according to Ṁ ∝ L^3/4, as expected for the results from recombination line analyses (cf., Hamann & Koesterke 1998). The symbols are the same as in Fig. 6.