We present precise radial velocities from a survey of 247 stars centered on Selected Area 57 at the North Galactic Pole, complete for late-type stars with V magnitude brighter than 12.0. The radial velocities have a typical precision of 0.2-0.3km/s. New spectral types and distances estimates are presented for 120 of the stars in the sample. We have considered all pairs of stars with angular separations between 1 and 600arcsec, and find 11 candidate pairs with velocity differences less than 1.5km/s. We estimate that 4 or 5 of the 11 candidate pairs are actually bound binaries, but none with separations larger than 0.1pc. The constraints imposed by these results on the actual distribution of wide binaries in the Galaxy should now be reanalyzed. The unusual precision of our velocities led to the discovery of a new cluster associated with the multiple system ADS 8811 ABC.
We have used the two-degree field (2dF) multi-fiber spectrograph of the Anglo-Australian Telescope (AAT) to search for candidate members of the unusual globular cluster omega Centauri at and beyond the cluster tidal radius. Velocities with an accuracy of ~10km/s were obtained for 4105 stars selected to lie in the vicinity of the lower giant branch in the cluster color-magnitude diagram (CMD) and which cover an area on the sky of ~2.4x3.9{deg}^2^ centered on the cluster.
We present the results obtained from a long-term spectroscopic campaign to study the multiplicity of O-type stars in both the young open cluster NGC 2244 and the Mon OB2 association. Our spectroscopic monitoring was performed over several years, allowing us to investigate different timescales. For each star, several spectral diagnostic tools were applied to search for line shifts and profile variations. We also measured the projected rotational velocity and revisited the spectral classification.
We have conducted a radial-velocity survey of bright (V<9), overluminous, F stars within 80pc. Of the total of 118 stars selected, the radial velocities of 77 have been measured with the Cambridge CORAVEL in the present survey.
The analysis of CORAVEL radial velocities of 93 stars selected on the basis of their proper motion and Geneva CCD photometric observations for 57 stars have permitted to identify 25 new members in the outer part of the Pleiades. Several spectroscopic binaries have been discovered, but their membership is not clear. Two orbits with short periods have been determined, but both stars are probably non-members. The total number of member stars in the outer part of the Pleiades in the spectral range F5-K0 (0.45<B-V<0.90) is now 81 which is comparable to the number of stars known in Hertzsprung's central area (88 stars) in the same spectral domain. Therefore at least 48% of the F5-K0 main-sequence stars are located in the outer part of the cluster. And the census is probably still incomplete.
The Population II radial velocity measurement programme was carried out in 1988-1993. Metal-deficient stars, components of Population II visual binaries or common proper motion stars, suspected radial velocity variables, Hipparcos programme stars are included into the observation programme. The measurements were made with the CORAVEL-type photoelectric radial velocity speedometer attached to the 1m reflector at the Mount Maidanak observatory (h=2560m, Uzbekistan). The average error of a single measurement is about 0.6km/s, but for the stars as faint as 13mag, or for extreme metal-deficient stars it drop down to 2.5km/s. 621 measurements for 164 stars are presented.
CORAVEL radial-velocity observations of Am stars in the Hyades and Praesepe have allowed the determination of orbital elements for 10 spectroscopic binaries, among which 3 are first determinations. One Am star (KW 40) is found to be a well hierarchised triple system. KW 538 has a rather long period (435 days) for an Am star. Orbits of systems with periods shorter than 8.5 days are circularized, or present eccentricities smaller than 0.04. For 19 Am stars, the number of quadruple-, triple-, double-, single systems is 1:2:14(10+4?):(2?). The Am stars in a ({beta}, B-V) diagram clearly stand away by 0.03mag from the sequence defined by normal main-sequence stars. This diagram could be a powerful method to identify Am stars in more distant open clusters, provided there is no differential reddening. In the colour-magnitude diagram (M_V_, {beta}), double-lined binaries are 0.6-0.7mag above the ZAMS as expected, while most single-lined are close to or on the ZAMS because the secondary does not contribute much light. The absence of X-ray detection of 4 systems in the Hyades is an argument for the presence of a white dwarf secondary.
Radial-velocity and BV CCD observations of 29 red-giant candidates in the central part of the intermediate-age open cluster NGC 1817 have confirmed the membership of 21 stars. In addition, we have used radial velocities and new UBVR photoelectric photometry to investigate the membership of 59 new candidates located in an outer corona surrounding NGC 1817, identified from the POSS plates. We have confirmed 18 new members out to a distance of 27' from the centre, thus doubling the previous cluster radius. Ten definite spectroscopic-binary members have been discovered, corresponding to a binary frequency of 25.6% and four orbits have been determined so far. Three additional stars have been identified as possible spectroscopic-binary members. We derive a cluster mean velocity of +65.33+/-0.09 (0.52 s.e.) km/s based on 29 members with no detected velocity variations plus the 3 binary members with orbital solutions.
We present the results of a survey of radial velocities over a wide region extending from r~=10 out to 80' (~1.5 tidal radii) within the massive star cluster omega Centauri (omega Cen). The survey was performed with FLAMES@VLT, to study the velocity dispersion profile in the outer regions of this stellar system. We derived accurate radial velocities for a sample of 2557 newly observed stars, identifying 318 bona fide cluster red giants. Merging our data with those provided by our previous survey, we assembled a final homogeneous sample of 946 cluster members that allowed us to trace the velocity dispersion profile from the centre out to r~32'.
We present a spectroscopic survey of 2079 red giant stars, distributed over the central 4kpcx2kpc of the Small Magellanic Cloud (SMC). After fitting and removing a small velocity gradient across the SMC (8.3km/s/{deg} oriented at 23.4{deg} east of north), we measure an rms velocity scatter of 27.5+/-0.5km/s.