Photoelectric Observations of Nova DQ Herculis (1934).

Observations of DQ Her obtained in 1955 and 1956 are presented. The mni results of this investigation are as follows: 1. The shape and depth of the eclipse-curve changed between 1954 and 1956. It is not possible to derive reliable photometric elements of the system from the 1956 observations, and the fact that the eclipse- curve has changed suggests that the elements derived in 1954 are also unreliable. 2. The 1-minute variations are investigated and found to be a strictly periodic phenomenon; the period has been derived over an interval of 1 day on July 5 and 6,1956, and the same period represents observations over an interval of 2 days on August 10,11, and 12,1956. The amplitude of the 1-minute variations varies with the phase in the 4-hour period. It is a maximum when the variations are first observed, just before the end of primary eclipse at 0.06F or 0.07P, and decreases to zero at about 0.5P on most nights. They are again visible for a short interval near 0.8FA).9P. There seem to be two possible interpretations: either the variations originate on the hemisphere of the old nova facing the secondary star, or the entire star pulsates and the variations are obscured by the detached material that produces the minimum at 0.7P. Neither hypothesis is entirely satisfactory. If it is assumed that these variations represent the fundamental period of pulsation of the old nova, then the density of the old nova is between 10 and 10 times that of the sun, depending upon the model assumed for the structure of the star. With the density derived in this manner, values of the radius and mass of the ex-nova are given for different assumed values of the effective temperature and distance modulus.