High angular resolution N-band observation of the silicate carbon star IRAS08002-3803 with the VLTI/MIDI instrument: Dusty environment spatially resolved

K. Ohnaka, T. Driebe, K. H. Hofmann, Ch Leinert, S. Morel, F. Paresce, Th Preibisch, A. Richichi, D. Schertl, M. Schöller, L. B.F.M. Waters, G. Weigelt, M. Wittkowski

Research output: Contribution to journalArticlepeer-review

51 Citations (Scopus)

Abstract

We present the results of N-band spectro-interferometric observations of the silicate carbon star IRAS08002-3803 with the MID-infrared Interferometric instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory (ESO). The observations were carried out using two unit telescopes (UT2 and UT3) with projected baseline lengths ranging from 39 to 47 m. Our observations of IRAS08002-3803 have spatially resolved the dusty environment of a silicate carbon star for the first time and revealed an unexpected wavelength dependence of the angular size in the N band: the uniform-disk diameter is found to be constant and ∼36 mas (72 R*) between 8 and 10 μm while it steeply increases longward of 10 μm to reach ∼53 mas (106 R*) at 13 μm. Model calculations with our Monte Carlo radiative transfer code show that neither spherical shell models nor axisymmetric disk models consisting of silicate grains alone can simultaneously explain the observed wavelength dependence of the visibility and the spectral energy distribution (SED). We propose that the circumstellar environment of IRAS08002-3803 may consist of two grain species coexisting in the disk: silicate and a second grain species, for which we consider amorphous carbon, large silicate grains, and metallic iron grains. Comparison of the observed visibilities and SED with our models shows that such disk models can fairly - though not entirely satisfactorily - reproduce the observed SED and W-band visibilities. Our MIDI observations and the radiative transfer calculations lend support to the picture where oxygen-rich material around IRAS08002-3803 is stored in a circumbinary disk surrounding the carbon-rich primary star and its putative low-luminosity companion.

Original languageEnglish
Pages (from-to)1015-1029
Number of pages15
JournalAstronomy and Astrophysics
Volume445
Issue number3
DOIs
Publication statusPublished - Jan 2006
Externally publishedYes

Keywords

  • Infrared: stars
  • Stars: AGB and post-AGB
  • Stars: carbon
  • Stars: circumstellar matter
  • Stars: individual: IRAS08002-3803
  • Techniques: interferometric

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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