2 Sample selection and observations

The most extensive catalog of active binaries remains the one of Strassmeier et al. (1993), which we have thus used as parent sample for our observing program. We have selected, from it, 28 systems (18 SB1 and 10 SB2), bright enough ($V \la 10$) to be observed with the instrument used (FEROS on the ESO 1.52 m telescope) at sufficiently high S/N in a reasonable time (1 hr maximum). We have made sure that a number of systems in our sample were also present in the work of Randich et al. (1994), in order to simplify the comparison of the two studies. The selected stars are all systems with moderate projected rotational velocity ( $v \sin i < 30$ km s^-1), to limit the blending of the lines.

The spectra were acquired in January 2000, with the fibre fed cross-dispersed echelle spectrograph FEROS, mounted on the ESO 1.52 m telescope at La Silla. The spectral range covered is 3600-9200 Å, with a resolution of 48 000. The spectral reduction (i.e. bias subtraction, flat field correction, order extraction and merging and wavelength calibration) has been performed during the observations with the "FEROS Data Reduction Software'' (URL: http://www.ls.eso.org/lasilla/Telescopes/2p2T/E1p5M/ FEROS/offline.html) available on the mountain. Most of the targets were observed 2 or 3 times (for a total of 49 spectra) to detect possible modifications of line profiles and allow a good filtering of the cosmic rays.

In this paper, 2 SB1 sample stars, IS Vir and V851 Cen, are analysed. Table 1 summarises their visual apparent magnitudes, number of exposures, mean resulting signal to noise ratios (per pixel) and projected rotational velocities, $v \sin i$, (from Strassmeier et al. 1993).

 

 

Table 1: Visual apparent magnitudes, number of exposures, mean resulting signal to noise ratios (per pixel) and projected rotational velocities (from Strassmeier et al. 1993) of IS Vir and V851 Cen.

HD Num.	Id.	V	Nb	S/N	$v \sin i$
					(km s-1)
HD 113816	IS Vir	8.32	3	170	6.0
HD 119285	V851 Cen	7.67	1	150	6.5