Volume 538, February 2012
|Number of page(s)||20|
|Section||Interstellar and circumstellar matter|
|Published online||27 January 2012|
Gas modelling in the disc of HD 163296
1 Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
2 University of Vienna, Dept. of Astronomy, Türkenschanzstr. 17, 1180 Vienna, Austria
3 UK Astronomy Technology Centre, Royal Observatory, Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
4 SUPA, School of Physics & Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, UK
5 Dep. de Física Teórica, Fac. de Ciencias, UAM Campus Cantoblanco, 28049 Madrid, Spain
6 ESA-ESAC Gaia SOC, PO Box 78. 28691 Villanueva de la Cañada, Madrid, Spain
7 Departamento de Astrofísica, Centro de Astrobiología (CAB, INTA-CSIC), ESAC Campus, PO Box 78, 28691 Villanueva de la Cañada, Madrid, Spain
8 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique (IPAG) UMR 5274, 38041 Grenoble, France
9 Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA
10 NASA Goddard Space Flight Center, Exoplanets & Stellar Astrophysics, Code 667, Greenbelt, MD 20771, USA
11 Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands
12 SOFIA-USRA, NASA Ames Research Center, Mailstop 211-3 Moffett Field CA 94035, USA
13 Astronomy Department, University of California, Berkeley, CA 94720-3411, USA
14 ESO-ALMA, Avda Apoquindo 3846, Piso 19, Edificio Alsacia, Las Condes, Santiago, Chile
15 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA, Leiden, The Netherlands
Received: 18 March 2011
Accepted: 2 November 2011
We present detailed model fits to observations of the disc around the Herbig Ae star HD 163296. This well-studied object has an age of ~4 Myr, with evidence of a circumstellar disc extending out to ~540 AU. We use the radiation thermo-chemical disc code ProDiMo to model the gas and dust in the circumstellar disc of HD 163296, and attempt to determine the disc properties by fitting to observational line and continuum data. These include new Herschel/PACS observations obtained as part of the open-time key program GASPS (GAS in Protoplanetary Systems), consisting of a detection of the [Oi] 63 μm line and upper limits for several other far infrared lines. We complement this with continuum data and ground-based observations of the 12CO 3–2, 2–1 and 13CO J = 1–0 line transitions, as well as an upper limit for the H2 0–0 S(1) transition. We explore the effects of stellar ultraviolet variability and dust settling on the line emission, and on the derived disc properties. Our fitting efforts lead to derived gas/dust ratios in the range 9–100, depending on the assumptions made. We note that the line fluxes are sensitive in general to the degree of dust settling in the disc, with an increase in line flux for settled models. This is most pronounced in lines which are formed in the warm gas in the inner disc, but the low excitation molecular lines are also affected. This has serious implications for attempts to derive the disc gas mass from line observations. We derive fractional PAH abundances between 0.007 and 0.04 relative to ISM levels. Using a stellar and UV excess input spectrum based on a detailed analysis of observations, we find that the all observations are consistent with the previously assumed disc geometry.
Key words: circumstellar matter / astrochemistry / stars: pre-main sequence / protoplanetary disks / stars: fundamental parameters / line: formation
© ESO, 2012
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