Multi-band Variability of the TeV Blazar PG 1553+113 with XMM-Newton

TL;DR

This study analyzes multi-year XMM-Newton observations of the TeV blazar PG 1553+113, revealing high intraday variability, co-spatial X-ray emission, and complex multi-timescale flux and spectral behaviors.

Contribution

It provides the first detailed variability analysis of PG 1553+113 across multiple timescales using XMM-Newton data, highlighting the co-spatiality of X-ray emissions and differing optical/UV and X-ray emission regions.

Findings

High intraday variability with ~84% duty cycle.

X-ray emissions are co-spatial in soft and hard bands.

Optical/UV and X-ray emissions originate from different lepton populations.

Abstract

We present variability analyses of twenty pointed XMM-Newton observations of the high energy peaked TeV blazar PG 1553+113 taken during 2010 to 2018. We found intraday variability in the total X-ray energy range (0.3 -- 10 keV) in 16 out of 19 light curves or a duty cycle of ~84%. A discrete correlation function analysis of the intraday light curves in the soft and hard X-ray bands peaks on zero lag, showing that the emission in hard and soft bands are co-spatial and emitted from the same population of leptons. Red-noise dominates the power spectral density (PSD) of all the LCs although the PSDs have a range of spectral slopes from -2.36 to -0.14. On longer timescales, the optical and UV variability patterns look almost identical and well correlated, as are the soft and hard X-ray bands, but the optical/UV variations are not correlated to those in the X-ray band, indicating that the optical/UV and X-ray emissions are emitted by two different populations of leptons. We briefly discuss physical mechanisms which may be capable of explaining the observed flux and spectral variability of PG 1553+113 on these diverse timescales.