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A Multicolor Study of AGNs and BL Lacs

Published online by Cambridge University Press:  12 April 2016

W.-H. Sun ,
Yu-Ya Su ,
Hsiao-Feng Tang ,
Matthew A. Malkan  and
Remington P. S. Stone
W.-H. Sun
Affiliation:
Institute of Astronomy, National Central University, Chung-Li, Taiwan 320, ROC
Yu-Ya Su
Affiliation:
Institute of Astronomy, National Central University, Chung-Li, Taiwan 320, ROC
Hsiao-Feng Tang
Affiliation:
Institute of Astronomy, National Central University, Chung-Li, Taiwan 320, ROC
Matthew A. Malkan
Affiliation:
Department of Astronomy, UCLA, Los Angeles, CA 90024, USA
Remington P. S. Stone
Affiliation:
Lick Observatory, ML Hamilton, CA 95064, USA

Abstract

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We present preliminary results of two monitoring projects on AGNs and BL Lacs with four intermediate-band optical filters at Lick Observatory, South African Astronomical Observatory, and Siding Spring Observatory. We applied differential photometry between the target and non-variable field stars to derive the variability amplitudes. All the AGNs varied in all wavebands, with amplitudes from 30% to 90%. The variations in shorter wavelength filters are always larger than in longer wavelength filters. We did not observe significant continuum slope changes. Continuum variations of BL Lacs up to 0.2 mag in 20 minutes were observed. Interestingly, we found a time lag of 6–8 minutes between two seemingly correlated variations observed in the intermediate U band with the 1-m telescope and in broad V band with the 24-in. telescope at SSO.

Type
I. X-Rays and the Nuclear Regions of Active Galaxies
Information
International Astronomical Union Colloquium , Volume 159: Emission Lines in Active Galaxies: New Methods and Techniques , 1997 , pp. 76 - 77
Copyright
Copyright © Astronomical Society of the Pacific 1997