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Post Info TOPIC: VV Serpens
Blobrana


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RE: VV Serpens
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Title: The dusty disk around VV Ser
Authors: T. Alonso-Albi, A. Fuente, R. Bachiller, R. Neri, P. Planesas, L. Testi

We have carried out observations at millimetre and centimetre wavelengths towards VV Ser using the Plateau de Bure Interferometer and the Very Large Array. This allows us to compute the SED from near infrared to centimetre wavelengths. The modelling of the full SED has provided insight into the dust properties and a more accurate value of the disk mass.
The mass of dust in the disk around VV Ser is found to be about 4 10^(-5) Msun, i.e. 400 times larger than previous estimates. Moreover, the SED can only be accounted for assuming dust stratification in the vertical direction across the disk. The existence of small grains (0.25--1 micron) in the disk surface is required to explain the emission at near- and mid-infrared wavelengths. The fluxes measured at millimetre wavelengths imply that the dust grains in the midplane have grown up to very large sizes, at least to some centimetres.

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Blobrana


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Title: Modelling Spitzer observations of VV Ser. I. The circumstellar disk of a UX Orionis star
Authors: Klaus M. Pontoppidan, Cornelis P. Dullemond, Geoffrey A. Blake, A. C. Adwin Boogert, Ewine F. van Dishoeck, Neal J. Evans, Jacqueline Kessler-Silacci, Fred Lahuis

We present mid-infrared Spitzer-IRS spectra of the well-known UX Orionis star VV Ser. We combine the Spitzer data with interferometric and spectroscopic data from the literature covering UV to submillimeter wavelengths. The full set of data are modelled by a two-dimensional axisymmetric Monte Carlo radiative transfer code. The model is used to test the prediction of (Dullemond et al. 2003) that disks around UX Orionis stars must have a self-shadowed shape, and that these disks are seen nearly edge-on, looking just over the edge of a puffed-up inner rim, formed roughly at the dust sublimation radius. We find that a single, relatively simple model is consistent with all the available observational constraints spanning 4 orders of magnitude in wavelength and spatial scales, providing strong support for this interpretation of UX Orionis stars. The grains in the upper layers of the puffed-up inner rim must be small (0.01-0.4 micron) to reproduce the colours (R_V ~ 3.6) of the extinction events, while the shape and strength of the mid-infrared silicate emission features indicate that grains in the outer disk (> 1-2 AU) are somewhat larger (0.3-3.0 micron). From the model fit, the location of the puffed-up inner rim is estimated to be at a dust temperature of 1500 K or at 0.7-0.8 AU for small grains. This is almost twice the rim radius estimated from near-infrared interferometry. A best fitting model for the inner rim in which large grains in the disk mid-plane reach to within 0.25 AU of the star, while small grains in the disk surface create a puffed-up inner rim at ~0.7-0.8 AU, is able to reproduce all the data, including the near-infrared visibilities.

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Position(2000): RA 18 28 47.86 Dec. +00 08 40.0

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