Abstract:
We present X-ray intraday variability and power spectral density (PSD) analyses of the longest 23 pointed XMM–Newton
observations of the blazar 3C 273 that were taken during 2000–2021. These good time intervals contain between 5 and 24.6 h of
data. Variability has been estimated in three energy bands: 0.2–2 keV (soft), 2–10 keV (hard), and 0.2–10 keV (total). 9 of the
23 observations exhibited some variability, though no major variations exceeding 5 per cent were detected. Typical time-scales
for variability were ∼1 ks. For those variable light curves, we find that a power-law model provides good fits to each PSD, with
most of the slopes between −1.7 and −2.8. Although no variations of hardness ratio (HR) could be measured in any individual
observation, an anticorrelation in flux and HR is found in long term data that indicates a harder when brighter trend. Our flux
and spectral analyses indicate that both particle acceleration and synchrotron cooling processes make an important contribution
to the emission from this blazar.
