The Ultraviolet Evolution of GQ Mus from 1986 to 1994

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Session 11 -- Novae
Display presentation, Monday, 9, 1995, 9:20am - 6:30pm

[11.03] The Ultraviolet Evolution of GQ Mus from 1986 to 1994

S. Starrfield (ASU), I. Idan (Technion), G. Shaviv (Technion), S. N. Shore (IUSB), J. Krautter (LSW), G. Sonneborn (LASP/GSFC)

GQ Mus has been observed by the International Ultraviolet Explorer (IUE) Satellite from soon after discovery until September 1994. These data provide the longest series of data for any nova in outburst. It was observed in X-rays by EXOSAT near the beginning of its outburst and, more recently, by ROSAT which, fortuitously, has measured its turn-off in X-rays (Shanly et al. 1994, preprint). We have now taken our extracted IUE spectra and used them to do ultraviolet photometry. We also used the 15 most recent SWP ``sky'' exposures to remove the artifacts from our longest exposures. This improved the noise level and removed the main artifact at $\sim$1500\AA. The ``skyflat'' was subtracted from the GQ Mus exposures which were then binned in 50\AA\ intervals. The binned fluxes centered at 1375\AA, 1575\AA, and 1825\AA\ were used to form synthetic ultraviolet colors for GQ Mus. These intervals were chosen to be as line free as possible. These colors were then used to produce an ultraviolet color-color diagram. We have now compared the colors of GQ Mus, over this 8 year period, to those of either hot white dwarfs (such as PG 1159-035 and H1504+65), cool white dwarfs, or theoretical accretion disk models for cataclysmic variables. We find that from 1986 to 1989 the colors of GQ Mus evolved through the region of hot white dwarfs toward those of cool white dwarfs. However, around the time that the turn-off began in X-rays, the colors shifted into the region occupied by accretion disks with mass accretion rates of $10^{18}$gm s$^{-1}$ where they have remained. Our results imply that, during the time of the X-ray ``on'' phase, there was no accretion disk in the binary system. However, once the X-rays began to turn off, an accretion disk reformed and is still present.

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