Has the Post-Nova Super-Soft X-ray Source GQ Muscae Turned Off?

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Session 46 -- Novae
Display presentation, Wednesday, 1, 1994, 9:20-6:30

[46.01] Has the Post-Nova Super-Soft X-ray Source GQ Muscae Turned Off?

L. Shanley, J.S. Gallagher, H. Ogelman (University of Wisconsin-Madison), M. Orio (Osservatorio Astronomico di Torino, Italy), J. Krautter (Landessternwarte, Germany)

The old nova GQ Muscae was detected in 1992 by ${\sl ROSAT}$ as a luminous "super-soft" X-ray source nearly a decade after outburst. While conforming to standard models if still burning, GQ Mus has remained "on" nearly five times longer than most other observed nova. We have observed Nova Muscae 1983 with the ${\sl ROSAT}$ PSPC in January 1993 and in September 1993 with effective exposure times of 4296 s and 100091 s respectively. In addition, CCD B band photometry was obtained over nearly one orbit on the CTIO 0.9-m contemporaneously with the January ${\sl ROSAT}$ observations. The X-ray count rate has declined by a factor of 100 since 1992. Yet, the CCD Photometry does not indicate an appreciable decrease in the optical nor is there a concomittent change in the amplitude of the modulation. GQ Mus has not reached its pre-outburst magnitude. Futhermore, recent spectral observations show that [Fe X] has disappeared and [N II] has returned also indicating a decrease in the temperautre. This presents us with a complex problem. The two luminosity components of the system, the X-ray and the optical, are not necessarily tied to the same source. A simple model of a hot white dwarf and an irradiated companion cannot explain the optical light curve. The asymetric optical modulation suggests some form of ongoing accretion, either via an elliptical disk or accretion columns along the magnetic field lines. Thus, we may ask if this is related to continued nuclear burning responsible for the longevity of GQ Mus? The question remains has the nova simply "turned off" or is there something else going on for which we have not accounted?

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