Spectroscopic binaries among Hipparcos M giants,. I. Data, orbits, and intrinsic variations
Abstract
Context: This paper is a followup on the vast effort to collect radial velocity data for stars belonging to the Hipparcos survey.
Aims: We aim at extending the orbital data available for binaries with M giant primaries. The data presented in this paper will be used in the companion papers of this series to (i) derive the binary frequency among M giants and compare it to that of K giants (Paper II); and (ii) analyse the eccentricity  period diagram and the massfunction distribution (Paper III).
Methods: Keplerian solutions are fitted to radialvelocity data. However, for several stars, no satisfactory solution could be found, even though the radialvelocity standard deviation is greater than the instrumental error, because M giants suffer from intrinsic radialvelocity variations due to pulsations. We show that these intrinsic radialvelocity variations can be linked with both the average spectralline width and the photometric variability.
Results: We present an extensive collection of spectroscopic orbits for M giants with 12 new orbits, plus 17 from the literature. On top of these, 1 preliminary orbit yielded an approximate value for the eccentricity and the orbital period. Moreover, to illustrate how the large radialvelocity jitter present in Mira and semiregular variables may easily be confused with orbital variations, we also present examples of pseudoorbital variations (in S UMa, X Cnc, and possibly in HD 115 521, a former IAU radialvelocity standard). Because of this difficulty, M giants involving Mira variables were excluded from our monitored sample. We finally show that the majority of M giants detected as Xray sources are actually binaries.
Conclusions: The data presented in this paper considerably increase the orbital data set for M giants, and will allow us to conduct a detailed analysis of the eccentricity  period diagram in a companion paper (Paper III).
Based on observations carried out at the Swiss telescope installed at the Observatoire de Haute Provence (OHP, France), and at the 1.93m OHP telescope. Full Tables 2, 3, and Table 6 are only available in electronic form at the CDS via anonymous ftp to cdsarc.ustrasbg.fr (130.79.128.5) or via http://cdsweb.ustrasbg.fr/cgibin/qcat?J/A+A/498/627
 Publication:

Astronomy and Astrophysics
 Pub Date:
 May 2009
 DOI:
 10.1051/00046361/200810698
 arXiv:
 arXiv:0901.0934
 Bibcode:
 2009A&A...498..627F
 Keywords:

 stars: binaries: spectroscopic;
 stars: latetype;
 stars: AGB and postAGB;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 17 pages, 15 figures, accepted for publication in A&