Long-term optical and radio monitoring of the quasars S5 0716+714 and 4C 38.41 on various time scales

Abstract

We present the results of long-term radio and optical monitoring of two radio-loud quasars. The aim of the work was to study the objects’ variability on various time scales and search for correlations between the radio and optical emission. The monitoring was performed in 2002–2010. The radio observations were carried out using the 22-m telescope of the Crimean AstrophysicalObservatory, 26-m telescope of the University of Michigan Radio Astronomy Observatory, and 14-m telescope of the Metsahovi Radio Observatory at 4.8, 8.0, 14.5, 22.2, and 36.8 GHz. The optical observations were obtained in the B, V,R bands using the Zeiss-1000 telescope of the Special Astrophysical Observatory with a CCD photometer. Light curves of the quasars 4C 38.41 (1633+382) and S5 0716+714 are presented. Radio flares of 4C 38.41 with amplitudes of 0.5–1.0 Jy at 4.8 and 8 GHz and 1–3 Jy at 22.2 and 36.8 GHz were detected on time scales of about 100 days. The amplitude of the optical brightness variations varied between 0.5^m and 1.5^m over about 200 days. The amplitudes of the flux variations for S5 0716+714 for the period of two months were 0.5–1.6 Jy at centimeter and 1–7 Jy at millimeter wavelengths. The amplitudes of flares in the optical reached 2^m in the B and V filters and 2.5^m in the R filter, on time scales of 200 days. The color indices of these objects did not change during the period covered by observations, i.e., the objects did not become bluer when they brightened. The detected delays between the variations atmillimeter and centimeter wavelengths are several days, which is within the interval between observations during the long-term monitoring. The absence of a distinct correlation between the optical and radio brightness variations was probably due to the presence of substantial time delays between the phenomena occurring in these different wavelength ranges.