Relationship Between Spectral Indices and Flux Variability of the Active Galactic Nuclei 3C 273

Abstract

We analyzed the correlation between flux variability and the corresponding spectral indices of the active galactic nuclei 3C 273, and found that there is a strong negative correlation between spectral indices and flux variability in the X-ray band, weaker negative correlation in the infrared and optical bands, and no obvious correlation in the ultraviolet band. The results tend to support the argument that when the brightness of the variations increases, the spectra become bluer. Furthermore, the discrete correlation function analysis reveals that there is significant time lags exist between the flux variability and its spectral indices.