2 CORAVEL star samples and binary content

  The star samples considered in this paper were observed with the CORAVEL spectro-velocimeters (Baranne et al. 1979) installed on the 1-m Swiss telescope at the Haute-Provence Observatory (France) and on the 1.54-m Danish telescope at the European Southern Observatory (La Silla, Chile). The criteria defining these various samples, their monitoring history and their binary content are described in the following subsections. For a detailed discussion of the binary frequency in the corresponding PRG family as a whole, we refer to the analysis paper (Jorissen et al. 1998).

  

Table 1: The sample of barium stars with strong anomalies (Ba4 or Ba5 on the scale defined by Warner 1965) monitored with CORAVEL. The spectral type, visual magnitude and B-V index are from Lü et al. (1983) or, if not available, from Lü (1991). The last column refers to a note at the end of the table providing the references where the orbital elements are to be found

a) DAO+ CORAVEL measurements.
c) Two classifications: Ba5 or S0. Appears in both tables.
d) CpD.
References to orbital elements: 0: Jorissen et al. (1998); 1: this paper; 2: Udry et al. (1998, Paper II); 6: Griffin et al. (1996); 7: Jorissen et al. (1995).

2.1 Strong barium stars

This sample includes the 28 barium stars with a strong anomaly (Ba4 or Ba5 on the scale defined by Warner 1965) from the list of Lü et al. (1983), not already monitored by McClure at the Dominion Astrophysical Observatory (DAO), plus the special star HD 46407 (see Sect. 2.4). These stars are presented in Table 1. The CORAVEL monitoring of that sample started in 1984 (preliminary results were presented in Jorissen & Mayor 1988). All the stars show radial-velocity variations due to binary motion except HD 19014 for which the situation is still unclear. Among the new spectroscopic orbits of strong barium stars, 18 are presented in Sect. 4. The others can be found in Paper II (8), in Griffin et al. (1996; 2) and in Jorissen et al. (1995; 1). The corresponding references are indicated in the last column of the table.

2.2 Mild barium stars

A random selection of 33 stars with a mild barium anomaly (Ba < 1, Ba1, Ba2 on the Warner scale, from the list of Lü et al. 1983) has been monitored since 1988 for comparison. A few mild barium stars observed by the Marseille team (see Paper II) for a different purpose were included in our initial sample later on. The global sample, also including 3 DAO stars (see next section), is presented in Table 2.

Among these mild barium stars, 27 stars are definitely binaries (3 with fixed parameters, and 6 with only a lower limit available on the orbital period), 3 are suspected binaries, 4 show no evidence of binary motion and 2 ( HD 65699 and HD 206778) are supergiants misclassified as mild barium stars (Smith & Lambert 1987; superscript "b'' in Table 2). Results for 14 mild barium stars are presented in Sect. 4. The remaining 13 binaries are to be found in Paper II (12) and in Griffin (1991; 1).

  

Table 2: The sample of barium stars with mild anomalies (Ba < 1, Ba1, Ba2 on the scale defined by Warner 1965) monitored with CORAVEL. The spectral type, visual magnitude and B-V index are from Lü et al. (1983) or, if not available, from Lü (1991). Column 6 gives a binarity flag (o: orbit, po: preliminary orbit with fixed parameters, mp: minimum period only available, sb: suspected binary, c: no radial-velocity variation). The last column refers to a note at the end of the table providing the references where the orbital elements are to be found

a) DAO+ CORAVEL measurements.
b) Misclassified as mild Ba star.
References to orbital elements: 0: Jorissen et al. (1998); 1: this paper; 2: Paper II; 12: Griffin (1991).

2.3 DAO stars

For several barium stars monitored by McClure, a few recent CORAVEL measurements, obtained in the framework of other projects, are nevertheless available. These new measurements often allow us to improve the DAO orbits, since they significantly increase the span of the monitoring. All these new orbital parameters are used in the analysis paper (Jorissen et al. 1998). The present paper and Paper II provide only four of these stars, 3 for which the number of CORAVEL measurements is fairly large ( HD 46407, HD 131670 and HD 223617) and 1 ( HD 196673) for which the 2 new available observations significantly change the period obtained by McClure & Woodsworth (1990). These stars are also included in Tables 1 and 2, where they are identified by a superscript "a'' in Col. 1. Their orbits are presented in Sect. 4 or in Paper II.

2.4 Two barium stars of special importance

  The K0Ba3 star HD 46407 and K2Ba2 star HD 218356 (=56 Peg) were included in the CORAVEL samples (Tables 1 and 2) because of their unique photometric behaviour among barium stars. HD 46407 exhibits long-term photometric variations in phase with the orbital motion (Jorissen et al. 1991; Jorissen 1997), whereas 56 Peg is a strong X-ray and UV source, indicating that it is an interacting binary system possibly hosting an accretion disk (Schindler et al. 1982; Dominy & Lambert 1983). A combined DAO/ CORAVEL orbit of HD 46407 is presented in Paper II whereas no clear orbital solution emerges for 56 Peg yet.

2.5 Non-variable S stars

  An initial sample of 9 S stars, whose monitoring started in 1984 (with preliminary results presented in Jorissen & Mayor 1988, 1992) was extended to 36 stars in 1988. This sample contains bright northern S stars from the General Catalogue of Galactic S Stars (GCGSS; Stephenson 1984) with no variable star designation, neither in the General Catalogue of Variable Stars (Kholopov et al. 1985) nor in the New Catalogue of Suspected Variable Stars (Kukarkin et al. 1982). The criterion of photometric stability has been adopted to avoid the confusion introduced by the envelope pulsations masking the radial-velocity variations due to orbital motion. Such a selection criterion clearly introduces a strong bias against intrinsically bright S stars.

The sample of 36 photometrically non-variable S stars is presented in Table 3. Among them, 24 are binaries (6 have only a lower limit available on the orbital period), 10 show no evidence for binary motion, and 2 ( HD 262427 and BD $+22^{\circ}4385$) are likely misclassified (Jorissen et al. 1998). The new spectroscopic binaries (18) are described in Sect. 4 (16) and in Carquillat et al. (1998; 2).

  

Table 3: The sample of photometrically non-variable S stars monitored with CORAVEL. The spectral type is from the GCGSS. The V magnitude and B-V index for S stars are from various sources, as listed in The General Catalogue of Photometric Data (GCPD; Mermilliod et al. 1997). In case no data are listed in the GCPD, the V magnitude from the GCGSS is listed. Column 6 gives a binarity flag (o: orbit, po: preliminary orbit with fixed parameters, mp: minimum period only available, j: jitter, c: no radial-velocity variation). The last column refers to a note at the end of the table providing the references where the orbital elements are to be found

b) star misclassified as S?
c) Two classifications: Ba5 or S0. Appears in both tables.
References to orbital elements: 0: Jorissen et al. (1998); 1: this paper; 3: Carquillat et al. (1998); 10: Jorissen & Mayor (1992).

2.6 Mira S stars, SC stars and Tc-poor carbon stars

A sample of 13 Mira S stars (Table 4) has also been monitored in order not to restrict the search for binaries to low-luminosity S stars (see Sect. 2.5). However, the envelope pulsations of Mira stars seriously hamper that search by causing a substantial radial-velocity jitter. This will be discussed in Sect. 5.

A sample of 7 SC and CS stars suffering the same problem has been monitored as well with CORAVEL, along with the 3 carbon stars lacking Tc from the list of Little et al. (1987). These stars are also listed in Table 4. Radial-velocity variations are observed for all these stars.

In case the photometric and radial-velocity periods are different, a tentative orbital solution is proposed. The results are presented in Sect. 5.

  

Table 4: The sample of Mira S stars, SC stars and C stars with no Tc lines, monitored with CORAVEL. The spectral type is from the GCGSS, and B-V from the GCPD