Astronomy and Astrophysics – Astronomy
Scientific paper
Nov 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998larm.confe.145s&link_type=abstract
"IX Latin American Regional IAU Meeting, "Focal Points in Latin American Astronomy", held in Tonantzintla, Mexico, Nov 9-13, 199
Astronomy and Astrophysics
Astronomy
Scientific paper
We present an analysis of the optical variability of a sample of 50 quasars from a photometric monitoring that has been conducted at Observatorio do Pico dos Dias (LNA, Brazil) since March 1993. The data analyzed here was collected between March 1993 and July 1996. The main distinctive characteristics of this monitoring is its high photometric precision, obtained with differential photometry techniques and CCD detectors, and the relatively good sampling of the light curves. We have analysed the data with respect to the variability dependence on luminosity and redshift, obtaining significant anti-correlations with both parameters. We have also verified that there is a trend for radio-loud objects to be more variable than the radio-quiets. We have concluded that, in these objects, a purely optical component would contribute with less than 30% to the total optical variability. We adopted a parameterization for the dependence of the variability on wavelength that turned out to be consistent with variability data found in literature. Structure function analysis, both of emsemble and individual light curves, has revealed that: 1) the observed trend for more luminous and higher redshift objects to be less variable is observed both in the quasar rest frame and in the observer rest frame; 2) there is a correlation between the the slope of the individual structure functions and the variability, that allows discarding the possibility of variability timescales to increase with the source luminosity. Finally, we verified that the dependence of the relative variability (sigma_L/L) on luminosity is consistent with predictions of a simple Poissonian model. The energy derived for the hipothetical pulses, of ~ 1050 erg, agrees well with those obtained in other studies. This work has been supported by FAPESP, CNPq and PRONEX.
Garcia Arnaldo
Sodre Laerte Jr.
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