Quasar optical variability: Searching for interband time delays (Research Note)

被引：0

作者：

Bachev, R.S. ^{[1
]}

机构：

[1] Institute of Astronomy, Bulgarian Academy of Sciences, 72 Tsarigradsko Chausse Blvd., 1784 Sofia, Bulgaria

来源：

Astronomy and Astrophysics | 2009年 / 493卷 / 03期

关键词：

Aims. The main purpose of this paper is to study time delays between the light variations in different wavebands for a sample of quasars. Measuring a reliable time delay for a large number of quasars may help constraint the models of their central engines. The standard accretion disk irradiation model predicts a delay of the longer wavelengths behind the shorter ones; a delay that depends on the fundamental quasar parameters. Since the black hole masses and the accretion rates are approximately known for the sample we use; one can compare the observed time delays with the expected ones. Methods. We applied the interpolation cross-correlation function (ICCF) method to the Giveon et al. sample of 42 quasars; monitored in two (B and R) colors; to find the time lags represented by the ICCF peaks. Different tests were performed to assess the influence of photometric errors; sampling; etc; on the final result. Results. We found that most of the objects show a delay in the red light curve behind the blue one (a positive lag); which on average for the sample is about +4 days (+3 for the median); although the scatter is significant. These results are broadly consistent with the reprocessing model; especially for the well-sampled objects. The normalized time-lag deviations do not seem to correlate significantly with other quasar properties; including optical; radio; or X-ray measurables. On the other hand; many objects show a clear negative lag; which; if real; may have important consequences for the variability models. © ESO 2009;

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摘要：

Journal article (JA)

引用

页码：907 / 911

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