AAS 198th Meeting, June 2001
Session 11. Cataclysmic Variables, Novae
Display, Monday, June 4, 2001, 9:20am-6:30pm, Exhibit Hall

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[11.04] Hubble Space Telescope Spectroscopic Observations of the Dwarf Nova RX Andromeda During Outburst Rise and Decline*

J. F. Sepinsky, E. M. Sion (Villanova Un.)

We report on Hubble Space Telescope (HST) observations of RX Andromeda (RX And) obtained during the initial rise to outburst and later during the decline into quiescence. We have carried out a synthetic spectral analysis of this system using model accretion disks and high gravity model photospheres. The spectra reveal strong absorption features due to CIII (1175Å), Lyman \alpha (1216Å), NIV (1238, 1242Å), SII (1260-65Å), SIII (1300Å), CII (1335Å), and SIV (1394, 1402Å). The flux has decreased by a factor of two on the decline spectrum. Our model accretion disk fits reveal that the absorption line spectrum and continuum energy distribution are well-represented by models with accretion rates of 10-8 M\odot per year. We present the results of multicomponent fitting involving a heated white dwarf plus the accretion disk. We use these models to characterize the evolution of the outburst. The second spectrum on the decline reveals the first detection of inverse P Cygni line profile structure, indicative of mass infall. We explore the nature of this infall and discuss its implications.

Acknowledgements: This work was supported by NASA grant GO6700.01-96A and by NSF Grant AST 99-01955 to Villanova University. Support was also provided by the NASA-Delaware Space Grant Consortium.

* Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

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