PERIODIC LIGHT-CURVE CHANGES FOR BETA-LYRAE

We apply a variety of classical and recently developed periodicity ana lyses to light curves of beta Lyrae in 9 eras that extend over a range of about 150 years. Some new data are tabulated. Most periodic variat ions that have been reported in the literature do not pass standard si gnificance tests, according to our adopted criteria. Certain other per iods do pass the tests, although most do so only for one, or at most t wo, data sets. Our main findings are that a period of about 9 months i s present in all data sets and that it connects extremely well in phas e from era to era, all the way back to Baxendell's observations of 184 0-1877. The semiamplitude is small but reasonably consistent, averagin g about 2% of the flux in the light curve maxima. Any substantially la rger excursions that occur are nonperiodic. Phase coherence of the 9 m onth period is fairly good, even with a linear ephemeris, and becomes excellent if one allows for a slow sinusoidal variation of the 9 month periodicity. There is some evidence for a monotonic decrease in the a mplitude of the 9 month periodicity with increasing wavelength. (C) 19 95 American Astronomical Society.