Detection of a subarcsecond dust shell around the Wolf-Rayet star WR 112

Abstract

A lunar occultation event of the Wolf-Rayet star WR 112 (type WC9) has been observed simultaneously from two independent telescopes at λ = 2.2 μm, allowing us to investigate this source with an angular resolution of ≈ 0.003 arcsec. We have detected a circumstellar dust envelope the brightness distribution of which can be approximately fitted by a Gaussian with a FWHM of ≈0.06 arcsec (≈ 1015> cm). We present and discuss the reconstructed brightness profile, which shows an asymmetry in the radial dust distribution. The derived dust grain temperature at the inner dust zone of ≈ 1150 K is consistent with available model calculations. There is no signature of the central star from our observations, providing a direct confirmation that the circumstellar shell emission dominates over the photospheric emission at 2.2 μm as predicted by fits to the spectral energy distribution. Further lunar occultation observations at different position angles are essential to reconstruct the two-dimensional image of the dust shell around WR 112. The current series of lunar occultations of WR 112 will continue to the end of 1999, and will be visible for all equatorial and southern latitude observatories.