A new approach to the variability characterization of active galactic nuclei

6th Young Researcher Meeting, L'Aquila 2015

Middei, R.^1 ; Vagnetti, F.^1 ; Antonucci, M.^1 ; Serafinelli, R.^1

Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, Roma

00133, Italy^1

关键词: Active galactic nuclei;    Cosmological effects;    Data release;    New approaches;    Sloan Digital Sky Survey;    Structure functions;    X ray bands;    XMM-Newton;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/689/1/012006/pdf
DOI  :  10.1088/1742-6596/689/1/012006

来源: IOP

【 摘 要 】

The normalized excess variance is a popular method used by many authors to estimate the variability of active galactic nuclei (AGNs), especially in the X-ray band. We show that this estimator is affected by the cosmological time dilation, so that it should be appropriately corrected when applied to AGN samples distributed in wide redshift intervals. We propose a formula to modify this estimator, based on the use of the structure function. To verify the presence of the cosmological effect and the reliability of the proposed correction, we use data extracted from the XMM-Newton Serendipitous Source Catalogue, data release 5 (XMMSSC-DR5), and cross-matched with the Sloan Digital Sky Survey quasar catalogue, of data release 7 and 12.