XMMVARAGN - Ensemble X-Ray Variability of AGN in 2XMMi-DR3
The authors find statistically consistent results for the two samples, with the SF described by a power law of the time lag tau, approximately as SF ~ tau0.1. They do not find evidence of the break in the SF, at variance with the case of lower luminosity AGNs. They confirm a strong anti-correlation of the variability with X-ray luminosity, accompanied by a change of the slope of the SF. They also find evidence in support of a weak, intrinsic, average increase of X-ray variability with redshift.
For XMM, the authors used the version of the Serendipitous Source Catalog then available, namely 2XMMi-DR3, the latest incremental update of the second version of the catalogue, with observations made between 2000 February 3 and 2008 October 08; all datasets were publicly available by 2009 October 31, but not all public observations are included in this catalog. The total area of the catalog fields is ~ 814 deg2, but taking account of the substantial overlaps between observations, the net sky area covered independently is ~ 504 deg2. The 2XMMi-DR3 catalogue contains 353,191 detections (above the processing likelihood threshold of 6), related to 262,902 unique X-ray sources, therefore a significant number of sources (41,979) have more than one record within the catalog.
The selected sources were cross-correlated with the DR7 edition of the SDSS Quasar Catalog (Schneider et al. 2010, AJ, 139, 2360) to obtain redshifts and spectral classifications for the sources. The authors used a maximum distance of 1.5 arcseconds, corresponding to the uncertainty in the X-ray positions, resulting in 412 quasars that were observed by XMM-Newton from 2 to 25 epochs each for a total of 1376 observations. The authors refer to these sources as the XMM-Newton sample.
Ensemble X-ray variability of active galactic nuclei from serendipitous source catalogues. Vagnetti F., Turriziani S., Trevese D. <Astron. Astrophys., 536, A84 (2011)> =2011A&A...536A..84V (SIMBAD/NED BibCode)
This number in order of increasing J2000.0 Right Acension uniquly identifies each source in this catalog.
The 2XMM or 2XMMi source designation, e.g., '2XMM/2XMMi JHHMMSS.s+DDMMSS', where the numerical part is the truncated J2000.0 equatorial coordinates of the source.
The Right Ascension of the source in the selected equinox. This was not explicitly given in the original reference table but was constructed by the HEASARC from the position-based name, and hence may be a little less accurate than the actual position given in the XMM-Newton Serendipitous Source Catalog, 2XMMi DR3 Version.
The Declination of the source in the selected equinox. This was not explicitly given in the original reference table but was constructed by the HEASARC from the position-based name, and hence may be a little less accurate than the actual position given in the XMM-Newton Serendipitous Source Catalog, 2XMMi DR3 Version.
The Galactic Longitude of the source.
The Galactic Latitude of the source.
The redshift of the AGN from the SDSS DR7.
The number of XMM-Newton observation epochs for the AGN.
The logarithm of the average X-ray flux of the AGN in the 0.5 - 4.5 keV band, in erg s-1 cm-2.
The logarithm of the average X-ray luminosity of the AGN in the 0.5 - 4.5 keV band, in erg s-1.
The logarithm of the minimum lag between any 2 epochs of the light curve in the source rest-frame, in days.
The logarithm of the maximum lag between any 2 epochs of the light curve in the source rest-frame, in days.