Spectroscopic characterization of a sample of southern visual binaries

¹ INAF – Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, 35122 Padova, Italy e-mail: desidera@pd.astro.it
² European Southern Observatory, Casilla 19001, Santiago, Chile

Received: 23 January 2006
Accepted: 22 February 2006

Abstract

Aims.We present the spectroscopic characterization of 56 pairs of visual binaries with similar components, based on high resolution spectra acquired with FEROS at ESO La Silla.

Methods.For all stars, we measured radial and rotational velocities and CaII H&K emission.

Results.Five previously unknown double lined spectroscopic binaries were found. Six other pairs show velocity differences that are not compatible with the orbital motion of the wide pair, indicating the presence of further companion(s) in the system. The fraction of visual binaries that contain additional spectroscopic components is %, compatible with other literature estimates. The ages of the components of the pairs derived from chromospheric activity typically show apparent differences of about 0.2 dex. A few pairs show a rather large difference in activity level, but in most cases this is consistent with the variability of chromospheric emission observed for the Sun along its magnetic cycle.