A ~4.6 h quasi-periodic oscillation in the BL Lacertae PKS 2155-304?

TL;DR

This paper reports a tentative detection of a ~4.6-hour quasi-periodic oscillation in the X-ray emission of blazar PKS 2155-304, based on a 64 ks observation, with analyses confirming the periodicity but limited by data duration.

Contribution

First detection of a potential ~4.6-hour X-ray QPO in PKS 2155-304, using multiple analysis methods on XMM-Newton data.

Findings

Detected ~4.6-hour QPO with ~5% modulation

Confirmed periodicity with periodogram, structure function, wavelet analyses

Limited by only 3.8 cycles observed, preventing strong claim

Abstract

We report a possible detection of an ~4.6-hour quasi-periodic oscillation (QPO) in the 0.3-10 keV emission of the high-energy peaked blazar PKS 2155-304 from a 64 ks observation by the XMM-Newton EPIC/pn detector. We identify a total modulation of ~5% in the light curve and confirm that nominal period by periodogram, structure function and wavelet analyses. The limited light curve duration allows the capture of only 3.8 cycles of this oscillation and thus precludes a very strong claim for this QPO, despite a nominally high (>3 sigma) statistical significance. We briefly discuss models capable of producing an X-ray QPO of such a period in a blazar.