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Abstract: We present new multi-wavelength millimeter interferometric observations ofthe Herbig Ae star HD 163296 obtained with the IRAM-PBI, SMA and VLA arraysboth in continuum and in the 12CO, 13CO and C18O emission lines. Gas and dustproperties have been obtained comparing the observations with self-consistentdisk models for the dust and CO emission. The circumstellar disk is resolvedboth in the continuum and in CO. We find strong evidence that the circumstellarmaterial is in Keplerian rotation around a central star of 2.6 Msun. The diskinclination with respect to the line of sight is 46+-4 deg with a positionangle of 128+-4 deg. The slope of the dust opacity measured between 0.87 and 7mm beta=1 confirms the presence of mm-cm-size grains in the disk midplane.The dust continuum emission is asymmetric and confined inside a radius of 200AU while the CO emission extends up to 540 AU. The comparison between dust andCO temperature indicates that CO is present only in the disk interior. Finally,we obtain an increasing depletion of CO isotopomers from 12CO to 13CO and C18O.We argue that these results support the idea that the disk of HD 163296 isstrongly evolved. In particular, we suggest that there is a strong depletion ofdust relative to gas outside 200 AU; this may be due to the inward migration oflarge bodies that form in the outer disk or to clearing of a large gap in thedust distribution by a low mass companion.

Autor: A. Isella INAF-Osservatorio Astrofisico di Arcetri, L. Testi INAF-OAA, A. Natta INAF-OAA, R. Neri IRAM, D. Wilner CFA, C. Qi CFA


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