Eccentric ellipsoidal red giant binaries in the LMC: complete orbital solutions and comments on interaction at periastron
Article first published online: 28 FEB 2012
© 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS
Monthly Notices of the Royal Astronomical Society
Volume 421, Issue 3, pages 2616–2628, April 2012
How to Cite
Nicholls, C. P. and Wood, P. R. (2012), Eccentric ellipsoidal red giant binaries in the LMC: complete orbital solutions and comments on interaction at periastron. Monthly Notices of the Royal Astronomical Society, 421: 2616–2628. doi: 10.1111/j.1365-2966.2012.20492.x
- Issue published online: 4 APR 2012
- Article first published online: 28 FEB 2012
- Accepted 2012 January 4. Received 2011 December 13; in original form 2011 August 15
- stars: AGB and post-AGB;
- binaries: close;
- stars: oscillations
Modelling ellipsoidal variables with known distances can lead to exact determination of the masses of both components, even in the absence of eclipses. We present such modelling using light and radial velocity curves of ellipsoidal red giant binaries in the Large Magellanic Cloud (LMC), where they are also known as sequence E stars. Stars were selected as likely eccentric systems on the basis of light curve shape alone. We have confirmed their eccentric nature and obtained system parameters using the Wilson–Devinney code.
Most stars in our sample exhibit unequal light maxima as well as minima, a phenomenon not observed in sequence E variables with circular orbits. We find evidence that the shape of the red giant changes throughout the orbit due to the high eccentricity and the varying influence of the companion.
Brief intervals of pulsation are apparent in two of the red giants. We determine pulsation modes and comment on their placement in the period–luminosity plane.
Defining the parameters of these systems paves the way for modelling to determine by what mechanism eccentricity is maintained in evolved binaries.