  The color-magnitude diagrams (CMDs) of young star clusters show that,
particularly at ultraviolet wavelengths, their upper main sequences (MSs)
bifurcate into a sequence comprising the bulk population and a blue periphery.
The spatial distribution of stars is crucial to understand the reasons for
these distinct stellar populations. This study uses high-resolution photometric
data obtained with the Hubble Space Telescope to study the spatial
distributions of the stellar populations in seven Magellanic Cloud star
clusters. The cumulative radial number fractions of blue stars within four
clusters are strongly anti-correlated with those of the high-mass-ratio
binaries in the bifurcated region, with negative Pearson coefficients < -0.7.
Those clusters generally are young or in an early dynamical evolutionary stage.
In addition, a supporting N-body simulation suggests the increasing percentage
of blue-MS stars from the cluster centers to their outskirts may be associated
with the dissolution of soft binaries. This study provides a different
perspective to explore the MS bimodalities in young clusters and adds extra
puzzles. A more comprehensive study combined with detailed simulations is
needed in the future.
