New spectroscopic binary companions of giant stars and updated metallicity distribution for binary systems

Bluhm, P. and Jones, M. I. and Vanzi, L. and Soto, M. G. and Vos, J. and Wittenmyer, R. A. and Drass, H. and Jenkins, J. S. and Olivares, F. and Mennickent, R. E. and Vuckovic, M. and Rojo, P. and Melo, C. H. F. (2016) New spectroscopic binary companions of giant stars and updated metallicity distribution for binary systems. Astronomy and Astrophysics, 593 (A133). ISSN 000-46361

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We report the discovery of 24 spectroscopic binary companions to giant stars. We fully constrain the orbital solution for 6 of these systems. We cannot unambiguously derive the orbital elements for the remaining stars because the phase coverage is incomplete. Of these stars, 6 present radial velocity trends that are compatible with long-period brown dwarf companions. The orbital solutions of the 24 binary systems indicate that these giant binary systems have a wide range in orbital periods, eccentricities, and companion masses. For the binaries with restricted orbital solutions, we find a range of orbital periods of between ~97–1600 days and eccentricities of between ~0.1–0.4. In addition, we studied the metallicity distribution of single and binary giant stars. We computed the metallicity of
a total of 395 evolved stars, 59 of wich are in binary systems. We find a flat distribution for these binary stars and therefore conclude that stellar binary systems, and potentially brown dwarfs, have a different formation mechanism than planets. This result is confirmed by recent works showing that extrasolar planets orbiting giants are more frequent around metal-rich stars. Finally, we investigate the eccentricity as a function of the orbital period. We analyzed a total of 130 spectroscopic binaries, including those presented here and systems from the literature. We find that most of the binary stars with periods .30 days have circular orbits, while at longer orbital periods we observe a wide spread in their eccentricities.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Access to Published version allowed due to publisher copyright policy.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Date Deposited: 22 Mar 2017 04:04
Last Modified: 22 Mar 2017 04:04
Uncontrolled Keywords: binaries; spectrographics; radial velocities
Fields of Research : 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Socio-Economic Objective: E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: 10.1051/0004-6361/201628459

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