Imaging the asymmetric dust shell around CI Cam with long baseline optical interferometry |
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| Authors: | N D Thureau J D Monnier W A Traub R Millan-Gabet E Pedretti J-P Berger M R Garcia F P Schloerb A-K Tannirkulam |
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| Institution: | School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS;University of Michigan, Astronomy dept., 914 Dennison bldg., 500 Church street, Ann Arbor, MI 40109, USA;Jet Propulsion Laboratory, California Institute of Technology, M/S 301–451, 4800 Oak Grove Drive, Pasadena, CA 91109, USA;Michelson Science Center, California Institute of Technology, 770 S. Wilson Ave. MS 100–22, Pasadena, CA 91125, USA;Laboratoire d'Astrophysique de l'Observatoire de Grenoble (LAOG), 414 rue de la Piscine, BP 53–X, Grenoble, France;Smithsonian Astrophysical Observatory, Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA;University of Massachusetts, Department of Astronomy, Amherst, MA 01003–4610, USA |
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| Abstract: | We present the first high angular resolution observation of the Be] star/X-ray transient object CI Cam, performed with the two-telescope Infrared Optical Telescope Array (IOTA), its upgraded three-telescope version (IOTA3T) and the Palomar Testbed Interferometer (PTI). Visibilities and closure phases were obtained using the IONIC-3 integrated optics beam combiner. CI Cam was observed in the near-infrared H and K spectral bands, wavelengths well suited to measure the size and study the geometry of the hot dust surrounding CI Cam. The analysis of the visibility data over an 8 yr period from soon after the 1998 outburst to 2006 shows that the dust visibility has not changed over the years. The visibility data show that CI Cam is elongated which confirms the disc-shape of the circumstellar environment and totally rules out the hypothesis of a spherical dust shell. Closure phase measurements show direct evidence of asymmetries in the circumstellar environment of CI Cam and we conclude that the dust surrounding CI Cam lies in an inhomogeneous disc seen at an angle. The near-infrared dust emission appears as an elliptical skewed Gaussian ring with a major axis a = 7.58 ± 0.24 mas , an axis ratio r = 0.39 ± 0.03 and a position angle θ= 35°± 2° . |
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| Keywords: | techniques: high angular resolution techniques: interferometric circumstellar matter stars: individual: CI Cam |
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