AAS 195th Meeting, January 2000
Session 25. Stars and Disks
Oral, Wednesday, January 12, 2000, 10:00-11:30am, Regency V

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[25.01] The Circumstellar Gas of \beta Pictoris: CO and \ion{C}{1}

A. Roberge, P.D. Feldman (JHU), A.M. Lagrange (Groupe d'Astrophysique de Grenoble), A. Vidal-Madjar, R. Ferlet (IAP), A. Jolly, J.L. Lemaire, F. Rostas (Observatoire de Paris-Meudon)

\beta Pictoris, the most extensively studied of the young planetary systems discovered in the last decade and a half, was early found to be surrounded by an edge-on disk of gas and dust. Gas at close to the radial velocity of the star is identified in all observations and called the stable gas component. In addition, spectra of \beta Pictoris show variable redshifted and blueshifted absorption features, at velocities ranging from tens to hundreds of km s-1 relative to the star. These features are the signatures of km-sized, possibly comet-like, bodies falling toward the star.

\ion{C}{1} and CO have been observed in the circumstellar disk. Since both these species should be destroyed by interstellar UV photons on short time scales, a secondary source for these gasses must exist. HST STIS high resolution echelle absorption spectra of these important species were obtained on December 6 and 19, 1997. These data will be used to illustrate the general properties of the circumstellar gas and to further explore the complicated nature of the \beta Pictoris system. Most importantly, we find that photodissociation of CO is not the primary source of \ion{C}{1} gas in the disk, contrary to previous suggestion. We also observe absorption features arising from the excited, metastable 1D state of \ion{C}{1} for the first time; the possible significance of these unique features will be discussed.

Support for this work at JHU was provided by grant GO-07512.01-96A from the Space Telescope Science Institute.

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

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