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Detection of non-radial pulsation and faint companion in the symbiotic star CH Cyg |
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| Authors: | E Pedretti † J D Monnier S Lacour W A Traub W C Danchi P G Tuthill N D Thureau R Millan-Gabet J-P Berger M G Lacasse P A Schuller F P Schloerb N P Carleton |
| Institution: | School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS;University of Michigan, Astronomy department, 914 Dennison bldg., 500 Church street, Ann Arbor, MI 40109, USA;Laboratoire d'Astrophysique de l'Observatoire de Grenoble (LAOG), 414 rue de la Piscine, BP 53-X Grenoble, France;Jet Propulsion Laboratory, California Institute of Technology, M/S 301–451, 4800 Oak Grove Drive, Pasadena, CA 91109, USA;NASA Goddard Space Flight Center, 8800, Greenbelt Road, Greenbelt, MD 20771, USA;School of Physics, Sydney University, NSW 2006, Sydney, Australia;Michelson Science Center, California Institute of Technology, 770 S. Wilson Ave. MS 100-22, Pasadena, CA 91125, USA;Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA;Institut d'Astrophysique Spatiale, Universit Paris–Sud, bâtiment 121, 91405 Orsay Cedex, France;University of Massachusetts, Astronomy Department, Amherst, MA 01003-4610, USA |
| Abstract: | 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 |
| Keywords: | techniques: high angular resolution techniques: interferometric binaries: symbiotic stars: imaging stars: individual: CH Cygni |