Can the Optical Fluctuations of 3C 273 be Random?

Abstract

Abstract. The fluctuations in optical brightness of the quasi-stellar object 3C 273 have been investiga ted 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.Although 3C 273 was not discovered to be a quasi-stellar object until 1963, we fortu nately have an 80-yr record of its optical brightness. It is bright enough at thirteenth magnitude to show up on old sky survey plates extending back to 1887. Harlan Smith and Dorrit Hoffleit (1963), examining these plates, found that 3C273 has been fluctuating in brightness by considerable amounts.