Query : 2017A&A...599A..82M

2017A&A...599A..82M - Astronomy and Astrophysics, volume 599A, 82-82 (2017/3-1)

A long-term study of AGN X-ray variability. Structure function analysis on a ROSAT-XMM quasar sample.


Abstract (from CDS):

Context. Variability in the X-rays is a key ingredient in understanding and unveiling active galactic nuclei (AGN) properties. In this band, flux variations occur on short timescales (hours) as well as on larger timescales. While short timescale variability is often investigated in single source studies, only a few works are able to explore flux variation on very long timescales.
Aims. This work aims to provide a statistical analysis of the AGN long term X-ray variability. We study variability on the largest time interval ever investigated for the 0.2-2keV band, up to approximately 20yr rest-frame for a sample of 220 sources. Moreover, we study variability for 2700 quasars up to approximatley eight years rest-frame in the same (soft) band.
Methods. We built our source sample using the 3XMM serendipitous source catalogue data release 5, and data from ROSAT All Sky Survey Bright and Faint source catalogues. To ensure that we selected AGN only, we used the Sloan Digital Sky Survey quasar catalogues data releases 7 and 12. Combining ROSAT and XMM-Newton observations, we investigated variability using the structure function analysis which describes the amount of variability as a function of the lag between the observations.
Results. Our work shows an increase of the structure function up to 20yr. We find no evidence of a plateau in the structure function on these long timescales.
Conclusions. The increase of the structure function at long time lags suggests that variability in the soft X-rays can be influenced by flux variations originated in the accretion disk or that they take place in a region large enough to justify variation on such long timescales.

Abstract Copyright: © ESO, 2017

Journal keyword(s): galaxies: active - quasars: general - X-rays: general - X-rays: general

Simbad objects: 3

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Number of rows : 3
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
1 NGC 3783 Sy1 11 39 01.7095761008 -37 44 19.008597647   12.46 13.43 11.33 12.1 ~ 1520 0
2 Mrk 509 Sy1 20 44 09.7504131334 -10 43 24.724854084   13.35 13.12 10.7   ~ 1170 0
3 UGC 12163 Sy1 22 42 39.3364258078 +29 43 31.301194419   14.86 14.16     ~ 640 1

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