A photoelectric study of the eclipsing binary RT Andromedae.

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The dwarf eclipsing system, RT Andromedae, has been studied photoelectrically for two reasons: (I) the photographic technique was found to be inadequate for resolving the light curve of a system of such short period, 0.6289 days, and (2) it seemed suitable for testing a technique of continuous recording of the light received. Three primary and one secondary minima were recorded without reference to a comparison star on an Esterline-Angus recorder attached to an amplifier and a I P2 I multiplier phototube on the ~6-inch refractor of the Lick Observatory. Observations were also made with a galvanometer by the standard photoelectric technique involving the use of a nearby star as a comparison. Analysis of the observations shows RT Andromedae to be a totally eclipsing system with a ratio of radii equal to more than 0.7. Primary minimum occurred at JD 2432443.7820 and the secondary minimum occurred one-half period later within the limits of accuracy of observation. The secondary minimum was considerably wider than the primary minimum; this difference in width led to a value of orbital eccentricity compatible with that found by S. Gaposchkin spectrographically, but ~ appeared to have changed by about 1700 in 1700 revolutions. These tests of the continuous-recording technique showed that the random errors of observation were lower than those produced by standard methods, but the systematic errors were somewhat higher. We may therefore conclude that the continuous-recording technique appears very valuable if a method of determining variations in atmospheric extinction and amplifier sensitivity is incorporated. A definitive solution of the elements on the basis of what would normally have been sufficient observing was precluded by evidence of intrinsic variability in the light of RT Andromedae. Further observations of this interesting system are planned. Lick Observatory, Mt. Hamilton, Cal~.