BASS-XL: X-ray variability properties of unobscured Active Galactic Nuclei

Kavli Affiliate: Claudio Ricci

| First 5 Authors: Alessia Tortosa, Claudio Ricci, Patricia Arévalo, Michael J. Koss, Franz E. Bauer

| Summary:

We investigate the X-ray variability properties of Seyfert1 Galaxies
belonging to the BAT AGN Spectroscopic Survey (BASS). The sample includes 151
unobscured (N$_{rm H}<10^{22}$ cm$^{-2}$) AGNs observed with XMM-Newton for a
total exposure time of ~27 Ms, representing the deepest variability study done
so far with high signal-to-noise XMM-Newton observations, almost doubling the
number of observations analysed in previous works. We constrain the relation
between the normalised excess variance and the 2-10 keV AGN luminosities, black
hole masses and Eddington ratios. We find a highly significant correlation
between $sigma^{2}_{NXS}$ and $M_{rm BH}$, with a scatter of ~0.85 dex. For
sources with high $L_{2-10}$ this correlation has a lower normalization,
confirming that more luminous (higher mass) AGNs show less variability. We
explored the $sigma^{2}_{NXS}$ vs $M_{rm BH}$ relation for the sub-sample of
sources with $M_{rm BH}$ estimated via the "reverberation mapping" technique,
finding a tighter anti-correlation, with a scatter of ~ 0.65 dex. We examine
how the $sigma^{2}_{NXS}$ changes with energy by studying the relation between
the variability in the hard (3-10 keV) and the soft (0.2-1 keV)/medium (1-3
keV) energy bands, finding that the spectral components dominating the hard
energy band are more variable than the spectral components dominating in softer
energy bands, on timescales shorter than 10 ks.

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