The circumstellar disc around the Herbig AeBe star HD169142

We present 7 mm and 3.5 cm wavelength continuum observations towards the Herbig AeBe star HD169142 performed with the Very Large Array (VLA) with an angular resolution of similar or equal to 1 arcsec. We find that this object exhibits strong ( similar or equal to 4.4 mJy), unresolved ( less than or similar to 1 arcsec) 7 mm continuum emission, being one of the brightest isolated Herbig AeBe stars ever detected with the VLA at this wavelength. No emission is detected at 3.5 cm continuum, with a 3 sigma upper limit of similar or equal to 0.08 mJy. From these values, we obtain a spectral index alpha greater than or similar to 2.5 in the 3.5 cm to 7 mm wavelength range, indicating that the observed flux density at 7 mm is most likely dominated by thermal dust emission coming from a circumstellar disc. We use available photometric data from the literature to model the spectral energy distribution (SED) of this object from radio to near-ultraviolet frequencies. The observed SED can be understood in terms of an irradiated accretion disc with low mass accretion rate, M-acc similar or equal to 10(-8) M-circle dot yr(-1), surrounding a star with an age of similar or equal to 10 Myr. We infer that the mass of the disc is similar or equal to 0.04 M-circle dot, and is populated by dust grains that have grown to a maximum size of 1 mm everywhere, consistent with the lack of silicate 10 m emission. These features, as well as indications of settling in the wall at the dust destruction radius, led us to speculate that the disc of HD169142 is in an advanced stage of dust evolution, particularly in its inner regions.