MULTIPERIOD PULSATION OF THE DELTA-SCUTI STAR 63-HERCULIS

Multisite photoelectric B and V photometry of the delta Scuti star 63 Her was obtained on three continents. Three frequencies of pulsation ( f1 = 11.32, f2 = 20.07 and f3 = 7.72 c/d) were detected with a signal/ noise amplitude ratio greater-than-or-equal-to 4.0. The three frequenc ies fit all the available data ranging back to 1968. Reports in the li terature of discrepant behavior of the 1968 measurements were probably caused by overinterpretation. The new frequency values are in excelle nt agreement with the results found by Reed & Welch from their 1983 da ta, except for a 1 c/d alias in their value for f2. Two additional pul sation frequencies in the low-frequency g-mode domain with amplitudes near two millimag reported by the STEPHI group are not seen in the new campaign data. The new data show average noise levels just below one millimage in this frequency domain, so that the existence of these two frequencies cannot be disproved from the new data alone. However, a r eanalysis of the STEPHI data also suggests that these frequencies migh t not be real. The results from the two multisite campaigns should be free of 1 c/d aliasing, so that a resonance hypothesis involving f2 = f1 + f3 can be rejected. The value of the pulsation constant associate d with f3, Q = 0.046 +/- 0.008 d, is too high by 2 standard deviations to be explained by radial pulsation. The Q value is incompatible with those of nonradial p1 to p4 modes commonly found in delta Scuti stars .