We have recently demonstrated that the nonlinear relation between ultraviolet and X-ray luminosity in quasars is very tight (with an intrinsic dispersion of ̃0.2 dex), once contaminants (e.g., dust reddening, X-ray absorption), variability, and differences in the active galactic nuclei physical properties are taken into account. This relation has thus great potential to advance our understanding in both supermassive black hole accretion physics and observational cosmology, by targeting a single class of objects. Here, we focus on the various contributions to the observed X-ray variability in a homogenous sample of 791 quasars selected from SDSS-DR7 with X-ray data from the 3XMM-DR7 source catalog. The 250 quasars in this cleaned data set with at least two X-ray observations typically vary with a SD of fractional variation of 15-30% on timescales of weeks/years. Yet, when the count rates are computed at progressively smaller off-axis values, the same quantity is reduced to roughly 10-25%. This suggests that, when estimating variability indicators, part of the quoted variability amplitude could be due to instrumental/calibration issues rather than true variations in the quasar emission.

The nonlinear X-ray/ultraviolet relation in active galactic nuclei: Contribution of instrumental effects on the X-ray variability / Lusso, E.*. - In: ASTRONOMISCHE NACHRICHTEN. - ISSN 0004-6337. - ELETTRONICO. - 340:(2019), pp. 267-272. (Intervento presentato al convegno XMM-Newton Workshop 2018, "Time-Domain Astronomy: A High Energy View") [10.1002/asna.201913608].

The nonlinear X-ray/ultraviolet relation in active galactic nuclei: Contribution of instrumental effects on the X-ray variability

Lusso, E.
2019

Abstract

We have recently demonstrated that the nonlinear relation between ultraviolet and X-ray luminosity in quasars is very tight (with an intrinsic dispersion of ̃0.2 dex), once contaminants (e.g., dust reddening, X-ray absorption), variability, and differences in the active galactic nuclei physical properties are taken into account. This relation has thus great potential to advance our understanding in both supermassive black hole accretion physics and observational cosmology, by targeting a single class of objects. Here, we focus on the various contributions to the observed X-ray variability in a homogenous sample of 791 quasars selected from SDSS-DR7 with X-ray data from the 3XMM-DR7 source catalog. The 250 quasars in this cleaned data set with at least two X-ray observations typically vary with a SD of fractional variation of 15-30% on timescales of weeks/years. Yet, when the count rates are computed at progressively smaller off-axis values, the same quantity is reduced to roughly 10-25%. This suggests that, when estimating variability indicators, part of the quoted variability amplitude could be due to instrumental/calibration issues rather than true variations in the quasar emission.
2019
The nonlinear X-ray/ultraviolet relation in active galactic nuclei: Contribution of instrumental effects on the X-ray variability
XMM-Newton Workshop 2018, "Time-Domain Astronomy: A High Energy View"
Lusso, E.*
File in questo prodotto:
File Dimensione Formato  
1812.03179.pdf

Open Access dal 20/03/2020

Tipologia: Pdf editoriale (Version of record)
Licenza: Tutti i diritti riservati
Dimensione 687.35 kB
Formato Adobe PDF
687.35 kB Adobe PDF

I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificatore per citare o creare un link a questa risorsa: https://hdl.handle.net/2158/1155462
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 5
  • ???jsp.display-item.citation.isi??? 5
social impact