Paper: astro-ph/0511261
Date: Wed, 9 Nov 2005 12:52:02 GMT (37kb)

Title: The circumstellar disc around the Herbig AeBe star HD169142

Authors: W. R. F. Dent (1), J. M. Torrelles (2 and 3), M. Osorio (4), N. Calvet
(5), G. Anglada (4) ((1) UK Astronomy Technology Centre, Royal Observatory
Edinburgh, UK, (2) Instituto de Ciencias del Espacio (CSIC)-IEEC Barcelona,
Spain, (3) On sabbatical leave at the UK Astronomy Technology Centre, Royal
Observatory Edinburgh, UK, (4) Instituto de Astrof\'{\i}sica de
Andaluc\'{\i}a (CSIC), Granada, Spain, (5) Dept. of Astronomy, University of
Michigan, St., Ann Arbor, MI, USA)

Comments: 13 pages, 2 figures. Accepted by MNRAS
\\
We present 7 mm and 3.5 cm wavelength continuum observations toward the
Herbig AeBe star HD169142 performed with the Very Large Array (VLA) with an
angular resolution of ~1". We find that this object exhibits strong (~4.4 mJy),
unresolved (~1") 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 ~0.08 mJy. From
these values, we obtain a spectral index of ~2.5 in the 3.5 cm to 7 mm
wavelength range, indicating that the observed flux density at 7mm 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, 10^{-8} solar masses per year, surrounding a star
with an age of ~10 Myr. We infer that the mass of the disc is ~0.04 solar
masses, and is populated by dust grains that have grown to a maximum size of 1
mm everywhere, consistent with the lack of silicate emission at 10 microns.
These features, as well as indications of settling in the wall at the dust
destruction radius, led us to speculate the disc of HD169142 is in an advanced
stage of dust evolution, particularly in its inner regions.

\\ ( http://arXiv.org/abs/astro-ph/0511261 , 37kb)