AAS 207th Meeting, 8-12 January 2006
Session 39 Circumstellar Disks
Oral, Monday, 10:00-11:30am, January 9, 2006, Delaware B

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[39.05] A New Inventory of Gas in the Beta Pictoris Debris Disk

A. Roberge (NASA-GSFC), P. D. Feldman (JHU), A. J. Weinberger (CIW -DTM), M. Deleuil, J.-C. Bouret (LAM)

We present the first detection of the important volatile species \ion{C}{2}, \ion{C}{3}, and most importantly, \ion{O}{1}, in the Beta Pic circumstellar disk. These species are seen in absorption against broad chromospheric emission lines in stellar spectra obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). They are present in the stable circumstellar gas component; additional redshifted components arising from star-grazing planetesimals are seen in the CII absorption lines. Combined with a previous measurement of CI gas, the \ion{C}{2} and \ion{C}{3} measurements complete the total inventory of stable atomic carbon gas in the disk. \ion{O}{1} is the only atomic oxygen species observed to date.

Previous observations of the Beta Pic circumstellar gas were primarily of metallic species. These new measurements permit a much more complete inventory of the gas, which, like the dust, is produced by the destruction of planetary material. We present a new compilation of the observed bulk gas composition. It is different from solar composition, nor is it similar to the composition of a carbonaceous chondrite meteorite or comet Halley dust. In particular, carbon is extremely overabundant. We calculate the total gas mass and gas-to-dust ratio for the disk, and compare them to recent theoretical constraints from analysis of the gas dynamics and the dust dynamics.

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