The Orbital Nature of 81 Ellipsoidal Red Giant Binaries in the Large Magellanic Cloud

Author(s): J. D. Nie, Peter R. Wood, Christine Nicholls
Abstract: In this paper, we collect a sample of 81 ellipsoidal red giant binaries in the Large Magellanic Cloud (LMC), and we study their orbital natures individually and statistically. The sample contains 59 systems with circular orbits and 22 systems with eccentric orbits. We derive orbital solutions using the 2010 version of the Wilson-Devinney code. The sample is selection-bias corrected, and the orbital parameter distributions are compared to model predictions for the LMC and to observations in the solar vicinity. The masses of the red giant primaries are found to range from about 0.6 to 9 M_⊙ with a peak at around 1.5 M_⊙ , in agreement with studies of the star formation history of the LMC, which find a burst of star formation beginning around 4 Gyr ago. The observed distribution of mass ratios q=m₂/m₁ is more consistent with the flat q distribution derived for the solar vicinity by Raghavan et al. than it is with the solar vicinity q distribution derived by Duquennoy & Mayor. There is no evidence for an excess number of systems with equal mass components. We find that about 20% of the ellipsoidal binaries have eccentric orbits, twice the fraction estimated by Soszynski et al. Our eccentricity evolution test shows that the existence of eccentric ellipsoidal red giant binaries on the upper parts of the red giant branch (RGB) can only be explained if tidal circularization rates are ˜1/100 the rates given by the usual theory of tidal dissipation in convective stars.
Organisation(s): Department of Astrophysics
External organisation(s): Chinese Academy of Sciences (CAS), Australian National University
Journal: The Astrophysical Journal
Volume: 835
No. of pages: 19
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-4357/835/2/209
Publication date: 02-2017
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/deaffb2c-f339-4d21-a84b-06bb54c57c4b

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