Study of the Nuclear Activity of the Seyfert Galaxy NGC 7469 over the Period of Observations 2008-2014

TL;DR

This study analyzes long-term optical and X-ray variability of Seyfert galaxy NGC 7469 from 2008 to 2014, revealing correlations, color changes with brightness, and a lag between X-ray and optical emissions, indicating complex accretion disk dynamics.

Contribution

It provides new insights into the long-term variability, color behavior, and X-ray/optical correlation and lag in NGC 7469 over multiple years, including effects of nearby supernova influence.

Findings

Long-term variability with a maximum in 2011-2012.

Color becomes bluer at brightness maxima, indicating higher disk temperature.

Strong correlation (0.93) between optical and X-ray variability in 2009 with a 2-4 day lag.

Abstract

We present results of multicolor UBVRI observations of the type 1 Seyfert galaxy (SyG 1) NGC 7469 carried out at the 1.5-meter telescope of the Maidanak Observatory (Uzbekistan) in 2008-2014. Analysis of the light curves indicates the presence of another slow flare of a long-term variability in 2009-2014 with a maximum in 2011-2012. We investigate properties of the long-term variability in 2009-2014, present (U-B)-(B-V) color diagrams for maxima and minima of NGC 7469 nuclear variability using various apertures and compare them with the black-body gas radiation which models the accretion disk radiation. Color-index measurements shows that the color becomes bluer at maximum brightness, indicating a higher temperature of the accretion disk. We have analysed the relation of X-ray and optical variability of NGC 7469 in 2008 and 2009 in comparison with the activity minimum in 2003. In 2008 the correlation coefficient between the X-ray and optical radiation is close to 0.5. Such poor correlation can be explained by the influence of an SN 1a explosion in close proximity to the nucleus of NGC 7469. The SN manifests itself in the optical band but does not affect the X-ray variability pattern. Comparison of the variability data in 2009 reveals a good correlation between the optical (U band) and the X-ray (7-10 keV) variability with the correlation coefficient of about 0.93. The correlation coefficient and the lag depend on the wavelength in the optical and X-ray bands. The lag between the X-ray and optical fluxes in 2009 is 2-4 days. In 2003 the lag is almost zero.