Description
We sought to determine the maximum age of Trapezium systems by studying possible trapezium systems that were selected independently of their occurrence in H II regions. We started with the unpublished catalog by Allen, Tapia & Parrao (1977RMxAA...3..119A) of all the known visual systems having three or more stars in which the maximum separation is less than 3.0 times the minimum separation. Their catalog has 968 such systems whose most frequent primary type is F, which does not describe young systems. With a CCD on the Kitt Peak 0.9m telescope we obtained UBV frames for 265 systems accessible with our equipment on Kitt Peak. The frames were used to obtain UBV photometry for about 1500 stars with an accuracy of 0.04mag between V=7 and 14mag. Also these frames were used to obtain astrometry with an accuracy of +/-0.015{deg} in position angle and +/-0.01" in separation. For the brightest star in each system we obtained a spectral type to determine the distance and reddening to the system.
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