Physics
Scientific paper
Dec 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992phdt.........9c&link_type=abstract
Ph.D. Thesis Florida Univ., Gainesville.
Physics
1
Active Galactic Nuclei, Data Correlation, Galactic Radiation, Light (Visible Radiation), Light Curve, Radio Waves, Cross Correlation, Discrete Functions, Quasars, Time Lag
Scientific paper
Long-term optical and radio light curves for a large sample of active galactic nuclei were investigated in order to examine the relationship between the two emission regions. Correlation analysis using the discrete correlation function was performed to determine if radio events are correlated with optical events, and, if so, to determine the lag times between them. In addition, similar analysis was performed to determine lag times between events at 14.5 GHz, 8.0 GHz, and 4.8 GHz. A total of forty-six objects were examined. Nine showed correlated optical and radio events with optical leading the radio in every case. Six of these were BL Lacertids, all having lag times of less than 6 months. The one QSO which showed correlated optical and radio events had a longer lag time, on the order of a year. No difference between BL Lacs and QSO's is seen in the results of correlation analysis on two radio frequencies. Lag times between 14.5 GHz and 8.0 GHz radio data are less than 5 months in almost every case. The same is true for lag times between 8.0 GHz and 4.8 GHz data. An additional nine objects showed no correlated behavior in their optical and radio light curves. Seven of these objects were QSO's. The rest of the objects either did not have light curves with adequate temporal coverage for reliable correlation analysis, or the analysis was confused by the number and spacing of events in one or both light curves. This analysis was seriously hampered by inadequate temporal coverage in the optical light curves. Some variability timescales in the optical are very short, making frequent observations necessary in order to resolve events. Unavoidable constraints on ground-based observations due to the weather, the sun, and the moon make it impossible to obtain the frequent, uninterrupted observations that are necessary to obtain a light curve without yearly gaps and with well-resolved short-term events.
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