Detection of Intra-day Variability Timescales of Four High Energy Peaked Blazars with XMM-Newton

TL;DR

This study analyzed XMM-Newton light curves of four high-energy peaked blazars to identify intra-day variability timescales and potential quasi-periodic oscillations, providing insights into their central black hole masses and emission mechanisms.

Contribution

It is the first comprehensive analysis of intra-day variability timescales in these four blazars using XMM-Newton data, including the detection of a likely QPO in PKS 2155-304.

Findings

Detected IDV timescales ranging from 15.7 ks to 46.8 ks.

Found a likely QPO in one light curve of PKS 2155-304.

Estimated black hole masses exceeding 1.2 × 10^7 solar masses.

Abstract

We selected a sample of 24 XMM-Newton light curves (LCs) of four high energy peaked blazars, PKS 0548-322, ON 231, 1ES 1426+428 and PKS 2155-304. These data comprise continuous light curves of 7.67h to 18.97h in length. We searched for possible quasi-periodic oscillations (QPO) and intra-day variability (IDV) timescales in the LCs of these blazars. We found a likely QPO in one LC of PKS 2155-304 which was reported elsewhere (Lachowicz et al. 2009). In the remaining 23 LCs we found hints of possible weak QPOs in one LC of each of ON 231 and PKS 2155-304, but neither is statistically significant. We found IDV timescales that ranged from 15.7 ks to 46.8 ks in 8 LCs. In 13 LCs any variability timescales were longer than the length of the data. Assuming the possible weak QPO periods in the blazars PKS 2155-304 and ON 231 are real and are associated with the innermost portions of their accretion disk, we can estimate that their central black hole masses exceed 1.2 $\times$ 10$^{7}$ M$_{\odot}$. Emission models for radio-loud active galactic nuclei (AGN) that could explain our results are briefly discussed.