The nature of the intranight variability of radio-quiet quasars

TL;DR

This study investigates the intranight optical variability of radio-quiet quasars, comparing observational data with three theoretical models, and finds the weak blazar component model most consistent with the data.

Contribution

It introduces a comparative analysis of three models explaining intranight variability in radio-quiet quasars, highlighting the potential role of a weak blazar component.

Findings

The weak blazar component model best explains the variability.

Detection probability varies between 20-80% depending on luminosity ratios.

X-ray irradiation could explain variability under specific spectral conditions.

Abstract

We select a sample of 10 radio-quiet quasars with confirmed intranight optical variability and with available X-ray data. We compare the variability properties and the broad band spectral constraints to the predictions of intranight variability by three models: (i) irradiation of an accretion disk by a variable X-ray flux (ii) an accretion disk instability (iii) the presence of a weak blazar component. We concluded that the third model, e.g. the blazar component model, is the most promising if we adopt a cannonball model for the jet variable emission. In this case, the probability of detecting the intranight variability is within 20-80%, depending on the ratio of the disk to the jet optical luminosity. Variable X-ray irradiation mechanism is also possible but only under additional requirement: either the source should have a very narrow Hbeta line or occasional extremely strong flares should appear at very large disk radii.