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Using near-infrared speckle interferometry we have obtained resolvedJHK-photometry for the components of 58 young binary systems. From thesemeasurements, combined with other data taken from literature, we derive massesand particularly mass ratios of the components. We use the J-magnitude as anindicator for the stellar luminosity and assign the optical spectral type ofthe system to the primary. On the assumption that the components within abinary are coeval we can then place also the secondaries into the HRD andderive masses and mass ratios for both components by comparison with differentsets of current theoretical pre-main sequence evolutionary tracks. Theresulting distribution of mass ratios is comparatively flat for M(2)/M(1) >0.2, but depends on assumed evolutionary tracks. The mass ratio is neithercorrelated with the primary's mass or the components' separation. Thesefindings are in line with the assumption that for most multiple systems in Tassociations the components' masses are principally determined by fragmentationduring formation and not by the following accretion processes. Only very fewunusually red objects were newly found among the detected companions. Thisfinding shows that the observed overabundance of binaries in the Taurus-Aurigaassociation compared to nearby main sequence stars should be real and not theoutcome of observational biases related to infrared observing.Comment: accepted by Astronomy and Astrophysics, contains extensive tables and  figures that will only be published electronically at CDS (in total: 34  pages, 11 figures

Mass ratios of the components in T Tauri binary systems and implications for multiple star formation