2009/05/01 by E. Pedretti, J. D. Monnier, S. Lacour +11 · 7 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Asymmetry #Brightness #Flux (metallurgy) #Infrared #Orbit (dynamics) #Orbital period #Position angle #Radial velocity #Stellar, planetary, and galactic studies #Telescope #astro-ph.IM #astro-ph.SR
paper · pdf · doi:10.1111/j.1365-2966.2009.14906.x
published in Monthly Notices of the Royal Astronomical Society 397(1), 325-334 (Oxford University Press) · 11 pages 5 figures, accepted MNRAS
arxiv created 2009/05/01 · openalex publication_date 2009/06/22 · arxiv updated 2015/05/13 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We have detected asymmetry in the symbiotic star CH Cyg through the measurement of precision closure phase with the Integrated Optics Near-Infrared Camera (IONIC) beam combiner, at the infrared optical telescope array interferometer. The position of the asymmetry changes with time and is correlated with the phase of the 2.1-year period found in the radial velocity measurements for this star. We can model the time-dependent asymmetry either as the orbit of a low-mass companion around the M giant or as an asymmetric, 20 per cent change in brightness across the M giant. We do not detect a change in the size of the star during a 3-year monitoring period neither with respect to time nor with respect to wavelength. We find a spherical dust shell with an emission size of 2.2 ± 0.1 D* full width at half-maximum around the M giant star. The star to dust flux ratio is estimated to be 11.63 ± 0.3. While the most likely explanation for the 20 per cent change in brightness is non-radial pulsation, we argue that a low-mass companion in close orbit could be the physical cause of the pulsation. The combined effect of pulsation and low-mass companion could explain the behaviour revealed by the radial velocity curves and the time-dependent asymmetry detected in the closure-phase data. If CH Cyg is a typical long secondary period variable then these variations could be explained by the effect of an orbiting low-mass companion on the primary star.