1 Introduction

This paper is the third one (see Udry et al. 1998a,b for the first two) in a series presenting new orbits obtained for barium and S stars as a result of a decade-long monitoring with the spectrovelocimeter CORAVEL (Baranne et al. 1979) installed on the 1-m Swiss telescope at the Haute-Provence Observatory (OHP, France).

The two S stars HR 363 (=HD 7351) and HD 191226, that are the subject of this paper, were put on the CORAVEL monitoring program by both the Toulouse and the Geneva-Brussels teams, as part of larger samples. The Toulouse team aims at obtaining orbital elements for a sample of bright late-type stars quoted in the literature as being spectroscopic binaries, but with no orbit available. For the Geneva-Brussels team, HD 191226 and HR 363 belong to a sample of Tc-poor S stars, a family of chemically-peculiar red giants suspected of being all binaries. A detailed discussion of the "binary paradigm'' for Tc-poor S stars can be found in Jorissen et al. (1998), and needs not be repeated here.

The new orbits of HD 191226 and HR 363 are provided in Sects. 2 and 3, respectively. Diagnostics of binary interaction are available for these two systems from published observations in the UV and X domains. The availability of their orbital elements now offers the possibility to correlate these diagnostics of binary interaction with the orbital separation, as discussed in Sect. 4.