AAS 200th meeting, Albuquerque, NM, June 2002
Session 85. Stars: Disks, Shells and Variability
Oral, Thursday, June 6, 2002, 2:00-3:30pm, Ballroom A

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[85.02] Observations of HDO and DCN in circumstellar disks around the protostars LkCa 15, MWC 480 and HD 163296

J.E. Kessler (Caltech), C. Qi (Harvard-Smithsonian CfA), G.A. Blake (Caltech)

Single dish and milimeter-wave interferometric imaging of disks of gas and dust surrounding several young T Tauri and Herbig Ae/Be stars have dramatically improved our understanding of disk physical and chemical structure. Such observations contribute to a more comprehensive understanding of star and planet formation. In particular, comparison of disk properties with those of comets and Kuiper Belt objects is invaluable in understanding our own Solar System in its infancy. Observations of deuterated species in circumstellar disks are particularly exciting in this respect, in that they should directly constrain the (D/H) fractionation in the outer (colder) regions of these disks and we can compare the extent of fractionation to that measured in comets such as Hale-Bopp (Blake et al. 1999) in order to investigate the origin of primitive solar system bodies.

In this study, the deuterated species DCN and HDO were observed toward the T Tauri protostar LkCa 15 and the Herbig Ae stars HD 163296 and MWC 480 using the Owen's Valley Radio Observatory Millimeter Array. Upper limits for the HDO in all three disks and DCN in LkCa 15 and HD 163296 were obtained. The deuterium fractionation was evaluated in each disk through the comparison of the resulting DCN abundances with previously observed HCN and H13CN abundances toward the same sources and the comparison of observed HDO abundances with predicted H2O abundances from chemical models, scaled by the CO(modeled)/CO(observed) abundances of the disks in our sample. The calculated deuterium fractionations in these three disks are compared to those obtained via chemical models and those observed for molecular clouds, hot cores, comets and solar system objects. In the cases where the signal to noise is high, the radial distribution of the emission will also be discussed.

This work was supported by the NASA Graduate Student Researchers Program, NGT5-50231, and the National Science Foundation, AST 9981546.

The author(s) of this abstract have provided an email address for comments about the abstract: kessler@caltech.edu

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.