Superhumps in Cataclysmic Binaries. II. PG 0917+342

Abstract

We have found a 113.1 minute periodicity in the light curve of the nova-like variable PG 0917+342. The signal is of 0.027 mag semiamplitude and appears to change its period slightly (ΔP/P ˜3 × 10-4) over the 1 yr baseline of observations. As this period is ˜5% longer than the spectroscopically determined orbital period, it seems to be another example of the "superhump" phenomenon which afflicts cataclysmic variables of short orbital period and high accretion rate. The rate of period change is ˜500 times smaller than that seen in the familiar superhumps of dwarf novae, presumably because changes of the accretion disk in this binary are much milder than those occurring in a dwarf nova. This interpretation implies that the hydrogen absorption lines should display a skewness variation with a period of 1.7 days.