GINGA observations of the old nova GK Persei in quiescence and outburst.

Ginga observations of the old nova GK Persei in quiescence, as well as a brief scanning observation during an outburst are reported. The X-ray spectrum in quiescence is well fitted by thermal bremsstrahlung emission of very high temperature (approximately 30 keV), plus an iron emission line. The outburst spectrum is complex and comprises two continua with different column densities (about 10 exp 23 and about 10 exp 24/sq cm). The 351-s spin modulation of GH Per was clearly detected in the quiescence observation, which confirms the results of previous Exosat observations. The folded light curve shows two peaks that are not separated by 180 deg in phase, which is quite different from the Exosat outburst data. It is similar to the Exosat observation at a similar flux level.