Six-color photometry of stars. VII. Light-curves of Eta Aquilae

LighPcurves of the variable star Aquilae have been obtained in six colors from the ultraviolet at 3530 A to the infrared at 10,300 A. The variations in all colors show the well-known hump in the light- curve about halfway down in the decreasing phase, with indications of other secondary fluctuations. The amplitudes of variation range from 1.45 mag. in the ultraviolet to 0.37 in the infrared. The times of maximum aud minimum come progressively later in the longer wave lengths, the displacement of phase being 0.05 period between 3530 A and 10,300 A, the same retardation that was found in Cephei. The colors of Aquilae at maximum nearly match those of supergiant stars of spectrnm cF7; at minimum they approximate cG3; but the variable is quite a typical star at either phase. The mean radius is found from the light- and , combined with an integrated velocity-curve, to be R = 4.7 X 10 km = 68Ro, a value somewhat larger than previous determinations. The period of this variable is shown to be lengthening at the present time.