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.

Middei, R., Vagnetti, F., Antonucci, M., Serafinelli, R. (2016). A new approach to the variability characterization of active galactic nuclei. ??????? it.cilea.surplus.oa.citation.tipologie.CitationProceedings.prensentedAt ??????? 6th Young Researcher Meeting, L'Aquila [10.1088/1742-6596/689/1/012006].

A new approach to the variability characterization of active galactic nuclei

VAGNETTI, FAUSTO;
2016-01-01

Abstract

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.
6th Young Researcher Meeting
L'Aquila
2015
Rilevanza internazionale
2016
Settore FIS/05 - ASTRONOMIA E ASTROFISICA
English
Intervento a convegno
Middei, R., Vagnetti, F., Antonucci, M., Serafinelli, R. (2016). A new approach to the variability characterization of active galactic nuclei. ??????? it.cilea.surplus.oa.citation.tipologie.CitationProceedings.prensentedAt ??????? 6th Young Researcher Meeting, L'Aquila [10.1088/1742-6596/689/1/012006].
Middei, R; Vagnetti, F; Antonucci, M; Serafinelli, R
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/144007
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