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Astron. Astrophys. 319, 481-486 (1997)

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2. Observations

A total of 243 radial-velocity observations were made of the ten programme stars during the period February 1983 through July 1995 with the photoelectric radial-velocity scanner CORAVEL (Baranne et al. 1979) on the Danish 1.54-m telescope at European Southern Observatory, La Silla, Chile. Its southern location, very good pointing accuracy and relatively large collecting area make this telescope well suited for the cluster programme. The limiting magnitude is B = 15.0. Integration times varied from 3 min. to about 20 min. depending on star brightness and seeing conditions. The positions and identifications of the binary red giants are listed in Table 1. References for the star numbering are given in Sect. 3 where individual systems are discussed.


[TABLE]

Table 1. Star positions and identifications


The radial velocities are on the southern system defined by Mayor & Maurice (1985), which is a natural system for the southern CORAVEL and corresponds to that of the fainter ([FORMULA]) IAU standard stars. Errors for the individual observations are derived following the precepts of Baranne et al. (1979) and are generally below 0.5 km s-1 for all the stars discussed here. In all ten systems, the radial-velocity variations are large enough (4 [FORMULA] K [FORMULA] 30 km s-1) to be clearly significant. The individual radial-velocity observations (Table 3) are available in electronic form only at the CDS via anonymous ftp (130.79.128.5). All the binaries discussed here are single-lined objects because the brighter and hotter A and early F-type companions usually show no dip, while the fainter secondary stars (G- and K-type dwarfs) are too faint to be detected.

UBV magnitudes and colours for the individual stars, the number of CORAVEL observations, and the time interval covered by them are given in Table 2 together with the orbital elements determined. No UBV magnitudes and colours are known for IC 2488 #25, but the Henry Draper Extension catalogue (HDE 300105) gives the spectral type G5 for this star. The periastron time [FORMULA] is expressed as [FORMULA] - 2440000.


[TABLE]

Table 2. General data and orbital elements for ten spectroscopic binaries


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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
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