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The Maximum Age of Trapezium Systems
We sought to determine the maximum age of Trapezium systems by studyingpossible trapezium systems that were selected independently of theiroccurrence in H II regions. We started with the unpublished catalog byAllen, Tapia, & Parrao of all the known visual systems having threeor more stars in which the maximum separation is less than 3.0 times theminimum separation. Their catalog has 968 such systems whose mostfrequent primary type is F, which does not describe young systems. Witha CCD on the Kitt Peak 0.9 m telescope we obtained UBV frames for 265systems accessible with our equipment on Kitt Peak. The frames were usedto obtain UBV photometry for about 1500 stars with an accuracy of+/-0.04 mag between V=7 and 14 mag. Also these frames were used toobtain astrometry with an accuracy of +/-0.015d in position angle and+/-0.01" in separation. For the brightest star in each system weobtained a spectral type to determine the distance and reddening to thesystem. The measures were used to determine physical membership fromstars that (1) fit a single color-magnitude diagram, (2) fit a commoncolor-color diagram, and (3) show no astrometric motion compared tovisual measures made (mostly) a century ago. Combining the results withspectroscopic data for 20 additional Allen et al. systems by Abt, wefound that 126 systems had only optical companions to the primaries, 116systems contained only a single physical pair, 13 were hierarchicalsystems with 3-6 members and having separation ratios of more than afactor of 10, two were small clusters, and only 28 fitted the criteriaof Trapezium systems. However, as shown by Ambartsumian, about 9% of thehierarchical systems should appear to be Trapezium systems inprojection. Those, like other hierarchical systems, have a broaddistribution of primary spectral types. We isolated 14 systems that seemto be true Trapezium systems. They have primary types of B3 or earlier,indicating a maximum age of about 5×107 yr. This upperlimit is consistent with the estimate made by Allen & Poveda for anage of several million years for these dynamically unstable systems.These Trapezia are also large with a median radius of 0.2 pc and amaximum radius of 2.6 pc. We asked why the sample of 285 possibleTrapezium systems yielded only 14 true ones, despite the attempt made byAllen et al. to eliminate optical companions with a ``1% filter,'' i.e.,demanding that each companion have less than a 1% chance of being afield star of that magnitude within a circle of its radius from theprimary. The explanation seems to be that the double star catalogs arebased mostly on BD magnitudes that, fainter than V=12 mag, aresystematically too faint by 1 mag.
| Mesures de vitesses radiales. VII. Accompagnement AU sol DU programme d'observation DU satellite Hipparcos. Radial velocities. VII. Ground based measurements for Hipparcos.
We publish 734 radial velocities of stars distributed in 28 fields of4x4deg. We continue the PPO series (Fehrenbach et al. 1987; Duflot etal. 1990 and 1992), using the Fehrenbach objective prism method.
| Equatorial coordinates of double and multiple star components measured on GPO astrographic plates
Equatorial coordinates are given for some of the multiple starcomponents having incomplete or inconsistent information in the IndexCatalog of Visual Double Stars. Two photographic plates were taken foreach system with incomplete or inconsistent information using the GPOastrograph. The plate measurement and reduction techniques used aredescribed.
| Visual multiples. VIII - 1000 MK types
A total of 1000 new classifications are given for stars brighter than B= 8.0 mag in the Aitken double star catalog. The classificationssupplement 865 classifications obtained in 1981 and 1984. Among thenewly discovered stars are 12 new Ap stars, eight Lambda Bootis stars,one Ba II star, and 60 Am stars. A detailed list of the newclassifications is given.
| Photometric Study of Trapezium-Type Systems
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979RMxAA...4..287E&db_key=AST
| Spectral types for early-type stars observed by SKYLAB
MK spectral types are presented for 246 early-type stars observed withthe S-019 ultraviolet stellar astronomy experiment on Skylab. K-linetypes are also given where applicable, and various peculiar stars areidentified. The peculiar stars include five silicon stars, a shell star,a helium-rich star, a silicon-strontium star, a chromium-europium star,and two marginal metallic-line stars.
| UBVRI photometry of stars in Trapezium type systems.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977RMxAA...3..133W&db_key=AST
| The kinematics of trapezium systems.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..101A&db_key=AST
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Observation and Astrometry data
| Constellation: | Zwillinge |
| Right ascension: | 06h21m14.48s |
| Declination: | +21°07'56.8" |
| Apparent magnitude: | 7.318 |
| Distance: | 248.139 parsecs |
| Proper motion RA: | -4.2 |
| Proper motion Dec: | -0.5 |
| B-T magnitude: | 7.226 |
| V-T magnitude: | 7.311 |
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