X-ray Intraday Variability and Power Spectral Density Profiles of the Blazar 3C 273 with XMM-Newton during 2000-2021

TL;DR

This study analyzes X-ray intraday variability and power spectral density profiles of blazar 3C 273 over two decades, revealing modest variability, typical timescales around 1 ks, and insights into emission processes.

Contribution

It provides the longest XMM-Newton observational analysis of 3C 273's X-ray variability, characterizing PSD slopes and flux-hardness correlations over 21 years.

Findings

Nine observations showed variability with no major changes.

PSD slopes mostly between -1.7 and -2.8 fit a power-law model.

Flux and hardness ratio are anti-correlated over long-term data.

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 contained between 5 and 24.6 hours 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). Nine of the 23 observations exhibited some variability, though no major variations exceeding 5 per cent were detected. Typical timescales for variability were $\sim 1$ 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 could be measured in any individual observation, an anti-correlation in flux and hardness ratio 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.