San Pedro Martir observations of microvariability in obscured quasars

TL;DR

This study investigates optical microvariability in obscured quasars using ANOVA, detecting rapid brightness fluctuations in two objects, which suggests that microvariability can be observed even in obscured AGNs.

Contribution

First application of ANOVA to detect optical microvariability in obscured quasars, demonstrating the method's effectiveness in challenging observational conditions.

Findings

Detected microvariability in two obscured AGNs.

Confirmed previous microvariability in Mrk 477.

Demonstrated statistical approach's viability in obscured AGN studies.

Abstract

Fast brightness variations are a unique tool to probe the innermost regions of active galactic nuclei (AGN). These variations are called microvariability or intra-night variability, and this phenomenon has been monitored in samples of blazars and unobscured AGNs. Detecting optical microvariations in targets hidden by the obscuring torus is a challenging task because the region responsible for the variations is hidden from our sight. However, there have been reports of fast variations in obscured Seyfert galaxies in X-rays, which rises the question whether microvariations can also be detected in obscured AGNs in the optical regime. Because the expected variations are very small and can easily be lost within the noise, the analysis requires a statistical approach. We report the use of a one-way analysis of variance, ANOVA, with which we searched for microvariability. ANOVA was successfully employed in previous studies of unobscured AGNs. As a result, we found microvariable events during three observing blocks: in two we observed the same object (Mrk 477), and in another, J0759+5050. The results on Mrk 477 confirm previous findings. However, since Mrk 477 is quite a peculiar target with hidden broad-line regions, we cannot rule out the possibility that we have serendipitously chosen a target prone to variations.