Spectroscopic binaries among Hipparcos M giants

Abstract

Context. This paper is a follow-up 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 mass-function distribution (Paper III). Methods. Keplerian solutions are fitted to radial-velocity data. However, for several stars, no satisfactory solution could be found, even though the radial-velocity standard deviation is greater than the instrumental error, because M giants suffer from intrinsic radialvelocity variations due to pulsations. We show that these intrinsic radial-velocity variations can be linked with both the average spectral-line 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 radial-velocity jitter present in Mira and semi-regular variables may easily be confused with orbital variations, we also present examples of pseudo-orbital variations (in S UMa, X Cnc, and possibly in HD 115 521, a former IAU radial-velocity 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 X-ray 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).

Roche-lobe filling factor of mass-transferring red giants: the PIONIER view

“…The object HD 190658 (V1472 Aql, HR 7680, HIP 98954) is a M2.5 III star in a binary system with a relatively short orbital period (P = 198.716 days; Lucke & Mayor 1982) -the second smallest in the sample of Famaey et al (2009). It is in a sense a sister system to the symbiotic star SS Lep, with a similar period, and therefore deserves further study.…”

A Catalog of GALEX Ultraviolet Emission from Asymptotic Giant Branch Stars

“…Independent of our study, Ortiz & Guerrero (2016) studied a volume-limited (< 500 pc) sample of 53 AGB stars detected by GALEX. This study includes the samples of Sahai et al (2008) and "confirmed" binary AGB stars derived from a radial velocity (RV) study by Famaey et al (2009) 5 . Ortiz & Guerrero (2016) esti-5 Sahai et al (2008 and Famaey et al (2009) remark on the complications that pulsations of AGB stars pose for RV measurements of such stars.…”

“…This study includes the samples of Sahai et al (2008) and "confirmed" binary AGB stars derived from a radial velocity (RV) study by Famaey et al (2009) 5 . Ortiz & Guerrero (2016) esti-5 Sahai et al (2008 and Famaey et al (2009) remark on the complications that pulsations of AGB stars pose for RV measurements of such stars. Nevertheless, Famaey et al (2009) conclude that some of the Mira and semi-regular variables they studied are mated the NUV and FUV flux in excess of photospheric emission based on stellar spectral templates and proposed that if an AGB star had a NUV excess ≥ 20 and/or if an AGB star is detected in FUV, then its UV emission indicates a binary companion.…”

“…Ortiz & Guerrero (2016) esti-5 Sahai et al (2008 and Famaey et al (2009) remark on the complications that pulsations of AGB stars pose for RV measurements of such stars. Nevertheless, Famaey et al (2009) conclude that some of the Mira and semi-regular variables they studied are mated the NUV and FUV flux in excess of photospheric emission based on stellar spectral templates and proposed that if an AGB star had a NUV excess ≥ 20 and/or if an AGB star is detected in FUV, then its UV emission indicates a binary companion. Applying the UV-based criteria, Ortiz & Guerrero (2016) inferred a binary fraction of ∼ 60% for their sample of AGB stars.…”

Evidence of a Mira-like tail and bow shock about the semi-regular variable V CVn from four decades of polarization measurements

“…Therefore, a binary companion is an implausible explanation for the observed polarization. We also note that Famaey et al (2009) found no evidence that V CVn is a spectroscopic binary.…”