10-micron interferometry of the disk and wind of the massive young star MWC349A

Abstract

We present VLTI-MIDI (the Mid-Infrared Interferometric Instrument at ESO's Very Large Telescope Interferometer) observations of MWC349 A, which are a prime example of the power of combined spatial and spectral resolution for addressing complex astrophysical phenomena. Previous observations of the peculiar emission line star MWC349A suggest that it is a young massive star in the short-lived phase of already having dissipated its parent cloud, but still being surrounded by the accretion disk, which is seen nearly edge-on. It is believed that the unique hydrogen recombination line maser / laser activity of MWC349A from mm to infrared wavelengths is also a consequence of this viewing geometry. We have taken 13 measurements with MIDI at the VLTI (Very Large Telescope Interferometer) in the GRISM mode covering the N band (8 to 13 microns) at a spectral resolution R ≈ 230. The wavelength dependence of the continuum visibility agrees with model calculations for circumstellar dust disks. In addition, the signatures of at least a dozen emission lines have been identified in the interferometric data. We present a first analysis of visibility amplitudes and differential phase data. In particular we show that a simple model can represent the SED and visibility amplitude of the continuum flux. Also the visibilities for the hydrogen and forbidden lines are discussed.