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[77.01] FUSE, HST, and Chandra Spectra of the Interstellar Gas and Dust toward X Persei

T. P. Snow, N. J. Cunningham, M. M. Drosback (CASA, University of Colorado), R. A. McCray (JILA, University of Colorado), B. L. Rachford (CASA, University of Colorado)

The line of sight toward the O9Vpe star X Persei (aka HD 24534) offers a unique opportunity to combine ultraviolet and X-ray spectra in order to assess the overall distribution of elements between the gas and the dust. The line of sight has a total visual extinction of approximately A_V = 2.05 mag and is known to contain high molecular abundances, placing this line of sight in the regime normally identified with translucent interstellar clouds. With apparent magnitude V = 6.10, X Per is bright enough to yield extremely high quality far-UV and UV spectra, allowing us to derive very accurate gas-phase column densities for a wide variety of atomic and molecular species. Our FUSE data show that this star has the highest hydrogen molecular fraction yet observed, and our HST data indicate unusually high depletions of some elements from the gas onto the dust. The star has an X-ray emitting companion which allows us also to use Chandra spectra to measure L- and K-shell absorption edges in order to determine the total elemental abundances, including contributions from both the gas and the dust in the line of sight. We discuss our results in the context of models of dust extinction and the overall distribution of gas and dust in the interstellar medium. This work has been supported by NASA grants GO0-1068X (Chandra) and GO-08623(HST), and contract 2430-600020 (FUSE), all to the University of Colorado.

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.