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Fig. 8


The mass of the most massive star of each association is plotted as a function of the number of bona fide OB members (black symbols). Red diamonds represent the average Mup  of all associations with the same number of members, their error bars being the standard deviation. The general trend is that Mup  increases with the number of members. Note however that some poorly populated associations (3-5 members) also have very high upper masses, as in the case of Orion’s Trapezium. The most populated association, #151 with 69 members, deviates from the main trend.

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