Continuum reverberation mapping of MCG 08-11-011

TL;DR

This study used photometric reverberation mapping to measure wavelength-dependent continuum lags in the AGN MCG 08-11-011, revealing larger-than-expected disk sizes and a steeper size-wavelength relation, suggesting additional emission components.

Contribution

First detailed multi-method photometric reverberation mapping of MCG 08-11-011, measuring continuum lags and revealing a steeper size-wavelength relation than standard models.

Findings

Measured inter-band lags up to 7 days.

Lag sizes exceed thin-disk predictions by a factor of 3-7.

Size-wavelength relation is steeper than expected, indicating additional emission contributions.

Abstract

We report the results from a photometric reverberation mapping campaign carried out with the C18 telescope at the Wise Observatory from 2019 to 2020, targeting the active galactic nucleus (AGN) MCG 08-11-011. The monitoring was conducted on a daily basis with specially designed narrow-band filters, spanning from optical to near-infrared wavelengths ($\sim4000$ to $8000${\AA}) and avoiding prominent broad emission lines. We aim to measure inter-band continuum time lags, determine the size-wavelength relation, and estimate the host-subtracted AGN luminosity for this system. We used the point-spread function photometry to extract the continuum light curves and measure the inter-band time lags using several methods, including the interpolated cross-correlation function, the z-transformed discrete correlation function, a von Neumann estimator, JAVELIN (in spectroscopic and photometric mode), MICA, and a multivariate correlation function. We find wavelength-dependent lags, $\tau(\lambda)$, up to $\sim$7 days between the multiband light curves of MCG 08-11-011. The observed lags are larger than predictions based on standard thin-disk theory by a factor of $\sim3-7$. We discern a significantly steeper ($\tau \propto \lambda^{4.74}$) size-wavelength relation than the $\tau \propto \lambda^{4/3}$ expected for a geometrically thin and optically thick accretion disk, which may result from the contribution of diffuse continuum emission to the flux. These results are similar to those found by previous continuum reverberation mapping campaigns.