The long-term optical variability of a composite, complete sample of quasars is investigated. While no correlation with luminosity is detected, a positive correlation with redshift is found (rho = 0.25). These results are reconciled with previous opposite findings of other authors, arguing that the analysis of variability can be biased by the combined effect of the structure function of light curves and of cosmological time dilation. Such bias becomes negligible if variability is measured by a magnitude difference at a fixed and large time lag (4 yr). Interpretation of this cosmological trend is given in terms of spectral variability. Statistical biases on the estimate of the evolution rate for the quasar population are discussed.

Giallongo, E., Trevese, D., Vagnetti, F. (1991). Optical variability of quasars: Statistics and cosmological properties. THE ASTROPHYSICAL JOURNAL, 377(2 PART 1), 345-348.

Optical variability of quasars: Statistics and cosmological properties

VAGNETTI, FAUSTO
1991-01-01

Abstract

The long-term optical variability of a composite, complete sample of quasars is investigated. While no correlation with luminosity is detected, a positive correlation with redshift is found (rho = 0.25). These results are reconciled with previous opposite findings of other authors, arguing that the analysis of variability can be biased by the combined effect of the structure function of light curves and of cosmological time dilation. Such bias becomes negligible if variability is measured by a magnitude difference at a fixed and large time lag (4 yr). Interpretation of this cosmological trend is given in terms of spectral variability. Statistical biases on the estimate of the evolution rate for the quasar population are discussed.
1991
Pubblicato
Rilevanza internazionale
Articolo
Sì, ma tipo non specificato
Settore FIS/05 - ASTRONOMIA E ASTROFISICA
English
Con Impact Factor ISI
COSMOLOGY; QUASARS
http://adsabs.harvard.edu/full/1991ApJ...377..345G
Giallongo, E., Trevese, D., Vagnetti, F. (1991). Optical variability of quasars: Statistics and cosmological properties. THE ASTROPHYSICAL JOURNAL, 377(2 PART 1), 345-348.
Giallongo, E; Trevese, D; Vagnetti, F
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/2108/44727
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