Imaging the asymmetric dust shell around CI Cam with long baseline optical interferometry

We present the first high angular resolution observation of the B[e] 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°.

[1]  Ž. Ivezić,et al.  Erratum: Self-similarity and scaling behaviour of infrared emission from radiatively heated dust — I. Theory , 1997 .

[2]  Wesley A. Traub,et al.  Recent results from the IOTA interferometer , 1998, Astronomical Telescopes and Instrumentation.

[3]  F. P. Schloerb,et al.  First Results with the IOTA3 Imaging Interferometer: The Spectroscopic Binaries λ Virginis and WR 140 , 2004, astro-ph/0401268.

[4]  F. P. Schloerb,et al.  Few Skewed Disks Found in First Closure-Phase Survey of Herbig Ae/Be Stars , 2006, astro-ph/0606052.

[5]  A. Miroshnichenko.  New possible binaries among B[e] stars , 1995 .

[6]  R. Maiolino,et al.  The optical-to-radio spectral energy distributions of low-metallicity blue compact dwarf galaxies , 2005, astro-ph/0501188.

[7]  Rafael Millan-Gabet,et al.  CHARA Michigan phase-tracker (CHAMP): design and fabrication , 2006, SPIE Astronomical Telescopes + Instrumentation.

[8]  L. Wood,et al.  From the Authors , 2003, European Respiratory Journal.

[9]  Spectroscopic observations of the candidate sgB(e)/X-ray binary CI Camelopardalis , 2002, astro-ph/0207026.

[10]  B. Krauskopf,et al.  Proc of SPIE , 2003 .

[11]  D. Allen.  Near Infra-Red Magnitudes of 248 Early-Type Emission-Line Stars and Related Objects , 1973 .

[12]  M. Rupen,et al.  CI Camelopardalis: A Shell-shocked X-Ray Nova , 2004, astro-ph/0407277.

[13]  Rafael Millan-Gabet,et al.  Michigan Infrared Combiner (MIRC): commissioning results at the CHARA Array , 2006, SPIE Astronomical Telescopes + Instrumentation.

[14]  Rafael Millan-Gabet,et al.  Robust determination of optical path difference: fringe tracking at the infrared optical telescope array interferometer. , 2005, Applied optics.

[15]  Rafael Millan-Gabet,et al.  An integrated-optics 3-way beam combiner for IOTA , 2003, SPIE Astronomical Telescopes + Instrumentation.

[16]  W. Lewin,et al.  Compact stellar X-ray sources , 2006 .

[17]  C. Beichman,et al.  Infrared Astronomical Satellite (IRAS) catalogs and atlases , 1988 .

[18]  Rafael Millan-Gabet,et al.  Spatially Resolved Circumstellar Structure of Herbig Ae/Be Stars in the Near-Infrared , 2000 .

[19]  Charles D. Bailyn,et al.  A Black Hole in the Superluminal Source SAX J1819.3–2525 (V4641 Sgr) , 2000, astro-ph/0103045.

[20]  S. T. Ridgway,et al.  First Results from the CHARA Array. II. A Description of the Instrument , 2005 .

[21]  G. Thomas.  Infrared Astronomical Satellite (IRAS). , 1986 .

[22]  Rafael Millan-Gabet,et al.  A NICMOS3 camera for fringe detection at the IOTA interferometer , 1999 .

[23]  et al,et al.  The Palomar Testbed Interferometer , 1999 .

[24]  J. McClintock,et al.  Compact Stellar X-Ray Sources: Black hole binaries , 2006 .

[25]  Rafael Millan-Gabet,et al.  The PICNIC Interferometry Camera at IOTA , 2004 .

[26]  A. Miroshnichenko,et al.  Properties of Galactic B[e] supergiants. I. CI Camelopardalis , 2002 .

[27]  William C. Danchi,et al.  Recent science results with the two-telescope IOTA , 2003, SPIE Astronomical Telescopes + Instrumentation.

[28]  B. W. Carroll,et al.  An Introduction to Modern Stellar Astrophysics , 1995 .

[29]  Qing-zhong Liu,et al.  Optical Spectroscopic Observations of CI Camelopardalis , 2007, 0806.4229.

[30]  E. L. Robinson,et al.  High-Dispersion Spectroscopy of the X-Ray Transient RXTE J0421+560 (=CI Camelopardalis) during Outburst , 2001, astro-ph/0110110.

[31]  A. Merand,et al.  A catalog of bright calibrator stars for 200-m baseline near-infrared stellar interferometry , 2005 .

[32]  Rafael Millan-Gabet,et al.  New beam-combination Techniques at IOTA , 2003, SPIE Astronomical Telescopes + Instrumentation.

[33]  W. Traub,et al.  Diameters of Mira Stars Measured Simultaneously in the J, H, and K' Near-Infrared Bands , 2004, astro-ph/0411073.

[34]  C. B. Markwardt,et al.  XTE J1739–302 as a Supergiant Fast X-Ray Transient , 2005, astro-ph/0510658.

[35]  R. Duinen.  Infrared Astronomical Satellite (IRAS) , 1977 .

[36]  G. Helou,et al.  Infrared astronomical satellite (IRAS) catalogs and atlases. Volume 7: The small scale structure catalog , 1988 .

[37]  M. Skrutskie,et al.  The Two Micron All Sky Survey (2MASS) , 2006 .

[38]  W. Lewin,et al.  On the Nature of XTE J0421+560/CI Camelopardalis , 1999, astro-ph/9907124.