TRAPEZIUM-TYPE
MULTIPLE
SYSTEMS*
G. N. S A L U K V A D Z E
Abastumani Astrophysical Observatory, Byurakan, U.S.S.R.
(Received 13 June, 1985) Abstract. Trapezium type multiple systems are one of the youngest systems in the galaxy. Ambartsumian (t954) regards many of the Trapezium-type multiple systems as having positive total energy. The examination of Table I, compiled from the Abastumani Catalogue of Trapezia (Salukvadze, 1978; Poveda et aL, 1977) and the Index Catalogue of KisualBinary Stars, shows that real trapezia are met among multiple stars with their primaries of O and B spectral types. TABLE I Spectral class of the primary O-B2 B3-B5-B B8-B9 A F G K M Unknown spectrum In all
Total number of multiple stars 59 72 118 394 309 224 153 11
Number of trapezia observed 39 23 25 60 41 33 37 8
Calculated number of pseudo trapezia 5 6 11 35 28 20 14 1
Probable number of real trapezia
Relative number of trapezia (%)
34 17 14 25 13 13 23 7
58 24 12 6 4 6 15 64 19
526
146
47
99
1867
412
167
245
Table II lists the results of a speciat investigation of the problem of relation of Trapezium-type systems with associations and galactic clusters (Salukvadze, 1979). TABLE II Spectral classes
O-B2 B3-B5 + 5 B8-B9 Unknown spectrum
Number of real trapezia
Number of trapezia belonging to
Percent of trapezia belonging to
Associations
Clusters
Associations
Clusters
33 16 13
27 12 8
2l 6 2
82 89 61
64 39 15
96
32
10
34
13
* Paper presented at the IAU Third Asian-Pacific Regional Meeting, held in Kyoto, Japan, between 30 September-6 October, 1984.
Astrophysics and Space Science 118 (1986) 321-323. 9 1986 by D. Reidel Publishing Company
322
G. N. SALUKVADZE
Trapezium-type multiple systems were also searched for in T-associations (Salukvadze, 1980a, b, 1981a). In 13 of them 120 trapezia were revealed. Out of these 85~o are real physical systems. The majority of trapezia are members of nebulae, and they are concentrated mainly in groups. A great deal of papers, from various investigators with quite different methods, have been devoted to the problem of trapezia stability. We shall not stop to consider them, but give only the results of our own investigations concerning this problem (S alukvadze, 1981b, 1982, 1985). Kinematics of 15 Trapezium-type multiple systems from the Abasturnani Catalogue with the primaries of O-B2 spectral classes have been specially studied. They are: ADS 719, 2783, 2843, 3709,4241,4728, 5322, 5977, 13374, 13626, 14526, 14831, 15184, 16095, 16381. It is found that out of these 15 studied Trapezia no less than 14 show expansion. As an example Figure 1 shows expansion of the Trapezium-type multiple system ADS 2843.
ADS 2843
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I
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I
I
I
13"0 4
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12.6
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6-10
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1960
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33.2 AC 4
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32.8
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1840
1
I
*1 i
1880
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L
1920
Finally it can be concluded that at present the statistical properties of trapezia are quite reliably determined. Consequently, it is of great importance to investigate individual trapezia. From this standpoint first of all it is necessary to estimate the photometric and spectral properties of stars making trapezia; and to determine the relative positions and radial velocities by which the problem of number of trapezia with positive total energy could be finally established.
TRAPEZIUM-TYPE MULTIPLE SYSTEMS
323
References Ambartsumian, V. A.: 1954, Bull. Bjurakan Obs. 15, 3. Poveda, A., Allen, C., and Warman, L.: 1977, Rev. Mex. Astron. Astrophys. 3, 127. Salukvadze, G. N.: 1978, Bull. Abastumani Astrophys. Obs. 49, 39. Salukvadze, G. N.: 1979, Astrophysics 15, 311. Salukvadze, G. N.: 1980a, Astrophysics 16, 505. Salukvadze, G. N.: 1980b, Astrophysics 17, 689. Salukvadze, G. N.: 1981a, Bull. Georgian SSR Acad. Sci. 101, 573. Salukvadze, G. N.: 1981b, Bull. Georgian SSR Acad. Sci. 104,1, 41. Salukvadze, G. N.: 1982, in Z. Kopal and J. Rahe (eds.), 'Binary and Multiple Stars as Tracers of Stellar Evolution', IAU Colloq. 69, 109. Salukvadze, G. N.: 1985, Astrophysics 22, 97.
