Broad-line region clouds orbiting an AGN sample

Abstract

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 (∼(3–28) × 1013 cm) is less than that of the eclipsing clouds with column densities of ∼1022–1023 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 ∼(0.3–3.6) $\times 10^4\, R_\mathrm{ g}$ 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 anticorrelation with a slope of −187 ± 62 between the known masses of the supermassive black hole in the centre of the galaxies with the equivalent width (EW) of the 6.4 keV Fe line for the five type 1 Seyfert galaxies of our sample, while the type 2 Seyfert galaxy NGC 7314 shows an average EW value of 100 ± 11 eV inconsistent with the above anticorrelation.