The old nova GK Per (1901). IV. The light curve since 1901.

The existing photometric data on GK Per (Nova Persei 1901) since the 1901 explosion have been collected. The light curve of the nova at minimum shows a gradual passage from continuous, irregular fluctuations (period 1916-1947) to the present situation in which the old nova spends most of its time at quiescence and, at intervals of several hundreds of days, produces enhanced outbursts (period 1948-1983). The photometric behavior can be understood in terms of an accreting, magnetic white dwarf. Irregular variations of the mass transfer rate (M) in the range 0.6 to 10 to the 17th g/s are responsible for the optical variability in the period 1916-1947; later (1948-1983) M is 2 x 10 to the 16th g/s at quiescence and increases up to 2 x 10 to the 18th g/s during outbursts.