Variability In A Low-Mass AGN: Oscillation Or Eruption?

TL;DR

This study analyzes X-ray variability in a low-mass AGN to determine if it exhibits quasi-periodic eruptions or oscillations, suggesting a continuum of variability mechanisms and exploring implications for similar galaxies.

Contribution

It provides a detailed analysis of variability in 2XMM J123103.2+110648, proposing a continuum between QPEs and QPOs, and reports no similar behavior in other low-mass AGNs.

Findings

Characteristic timescales of ~13.5 ks and ~14.4 ks identified.

Gaussian models fit the lightcurves better than sinusoidal models.

No evidence of QPE or QPO behavior in other low-mass AGNs studied.

Abstract

Following the discovery of a new class of X-ray variability seen in four galaxies, dubbed Quasi-Periodic Eruptions (QPEs), we reconsider the variability seen in the low-mass AGN 2XMM J123103.2+110648 to ascertain whether it should be considered the fifth QPE host galaxy. We apply the autocorrelation function to two archival XMM-Newton observations to determine characteristic timescales for variability of $\sim$ 13.52 ks and $\sim$ 14.35 ks. The modelling of lightcurves, both folded at these timescales and unfolded, indicates that a Gaussian model is preferable over a sinusoidal model, with average durations for the bright phases of 6.17 ks and 7.69 ks. In a broad 0.2-1.0 keV band the average amplitude of the bright phases was found to be 2.86 and 8.56 times the quiescent count rate. The pattern of variability seen in 2XMM J123103.2+110648 cannot be definitively declared as a series of Quasi-Periodic Eruptions. Instead, this suggests there may be a continuum of quasi-periodic variability ranging from eruptions to oscillations being caused by a single mechanism. This offers the possibility of finding further sources that continue to bridge the gap between QPEs and Quasi-Periodic Oscillations. A targeted analysis of 47 observations of 11 other low-mass AGN $(log(M_{BH}) \lesssim 6)$ found no evidence of QPE or QPO-like behaviour in a sample of other similar mass objects.