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Published online by Cambridge University Press: 14 August 2015
The fluctuations in optical brightness of the quasi-stellar object 3C 273 have been investigated to determine whether the suggested periodicity of ∼ 10 yr is supported by the observational data extending over 80 yr. New methods of obtaining information from the power spectrum have been used, and moments and trends have also been investigated. No statistically-supportable evidence has been found in the power spectrum for such a non-random variation. The moments and trends are consistent with random fluctuations. If the observed fluctuations are of shot-noise character, due to random outbursts of light, the individual pulses must occur at the rate of 15 ± 5 per year and have an average effective length of 3.2 ± 1 yr. These conclusions were verified by computer-generation and power-spectrum analysis of such random signals. Thus any periodic variation in the brightness of 3C 273, if present, is completely obscured by random fluctuations. The power spectrum, moments, and trend are all consistent with random but long-lasting outbursts of light.