Broad-line Region Clouds orbiting an AGN sample

TL;DR

This study analyzes X-ray data from six active galaxies to identify and characterize eclipsing clouds near their supermassive black holes, revealing properties consistent with broad-line region clouds and their impact on X-ray variability.

Contribution

It provides the first detailed estimates of the physical properties and locations of eclipsing clouds in multiple AGNs using spectral and temporal analysis of XMM-Newton data.

Findings

Eclipsing clouds are consistent with broad-line region clouds in several AGNs.

The size of X-ray sources is estimated to be smaller than the eclipsing clouds.

An anti-correlation between black hole mass and Fe line EW is observed in Seyfert 1 galaxies.

Abstract

We present a spectral and temporal analysis of XMM-Newton data from a sample of six galaxies (NGC 3783, Mrk 279, Mrk 766, NGC 3227, NGC 7314, and NGC 3516). Using the hardness-ratio curves, we identify time-intervals in which clouds are eclipsing the central X-ray source in five of the six sources. We detect three occultations in NGC 3227 and one occultation in NGC 3783, NGC 7314, and NGC 3516, together with the well-known occultations in Mrk 766. We estimate the physical properties of the eclipsing clouds. The derived physical size of the X-ray sources ($\sim$(3-28)$\times$10$^{13}$ cm) is less than that of the eclipsing clouds with column densities of $\sim$10$^{22}$-10$^{23}$ cm$^{-2}$, thus a single cloud may block the X-ray source, leading to notorious temporal variability of the X-ray flux. The eclipsing clouds in Mrk 766, NGC 3227, NGC 7314, and NGC 3516 with distances from the X-ray source of $\sim$(0.3-3.6)$\times$10$^4$ $R_g$ are moving at Keplerian velocities $>$1122 km s$^{-1}$, typical parameters of broad-line region clouds, while the eclipsing cloud in NGC 3783 is likely located in the dusty torus. We also find a good anti-correlation with a slope of -187$\pm$62 between the known masses of the supermassive black hole in the center of the galaxies with the equivalent width (EW) of the 6.4 keV Fe line for the five Seyfert 1 galaxies of our sample, while the Seyfert 2 galaxy NGC 7314 shows an average EW value of 100$\pm$11 eV inconsistent with the above anti-correlation.