It is well known that the observational data on double and multiple stars suffer from severe incompleteness. Limitations of our observing techniques are not the only reason for it; yet another reason of incompleteness is that just a small fraction of systems was observed systematically by all relevant methods. This is particularly true with respect to radial velocities, as only stars brighter that were observed spectroscopically in a more or less systematic way.
This is why I started in 1994 a program of radial velocity measurements of double and multiple stars, with particular emphasis on faint components. A couple of short-period orbits already resulted from this program (Tokovinin 1994; Tokovinin & Smekhov 1995). This paper presents another 7 orbits. These spectroscopic components were discovered independently; however, 2 of them have previously published indications of velocity variability, and one has a spectroscopic orbit (see discussion of individual systems below).
A correlation Radial-Velocity-Meter (RVM) (Tokovinin 1987) was used for the measurements. Observations were made mostly in 1994-1995 with the 70-cm telescope located on the Moscow University campus and with the 1-m telescope of the Simeis Observatory in Crimea. Velocity zero point was determined by observations of several IAU velocity standards each night. Some observations were also made by the author in 1994 with the CORAVEL spectrometer (Baranne et al. 1979) at the Haute Provence Observatory.
Table 1 (click here) contains the identification data on the 7 systems: IDS (1900) index, ADS number (Aitken 1932), HD or BD number, equatorial coordinates for 2000.0 and other identifiers, e.g. double star discoverer codes. The ADS number is a common identifier for all these systems and it will be used throughout this paper.
Basic data on system components (spectral types, visual magnitudes and B-V colors) are given in the left columns of Table 2 (click here) and were collected from the literature or taken from SIMBAD. Most of the photometry is from Eggen (1963). The last 3 columns of Table 2 (click here) summarize the results of our study and contain the mean equivalent width (EW) of the cross-correlation (CC) dip with its error, the projected axial rotational velocity and its error (as found from the width of CC dip), and mean radial velocities (the velocity taken from literature is marked with asterisk). The method of determination and the dependence of EW on B-V color and metallicity can be found in (Tokovinin 1990).
Figure 1: Radial velocity curve of ADS 1315C
Figure 2: Radial velocity curve of ADS 1849A = HR 710. Our measurements are plotted as squares, those of Bonsack (1981) as stars
Figure 3: Radial velocity curve of ADS 3608C. Solid line and squares refer to the primary component, dashed line and stars refer to the secondary component
Figure 4: Radial velocity curve of ADS 3824C = HR 1706C
Figure 5: Radial velocity curve of ADS 3991A. Our measurements of primary and secondary components are plotted as squares and stars, respectively. Data of Beavers & Eitter (1986) for the primary are plotted as triangles
Figure 6: Radial velocity curve of ADS 6646A
Figure 7: Radial velocity curve of ADS 8861A = Gliese 507A
Table 1: Object identification
Table 2: Basic observational data
Table 3: Orbital elements
Table 5: Models of multiple systems