Radio and optical intra-day variability observations of five blazars

Abstract

We carried out a pilot campaign of radio and optical band intra-day\nvariability (IDV) observations of five blazars (3C66A, S5 0716+714, OJ287,\nB0925+504, and BL Lacertae) on December 18--21, 2015 by using the radio\ntelescope in Effelsberg (Germany) and several optical telescopes in Asia,\nEurope, and America. After calibration, the light curves from both 5 GHz radio\nband and the optical R band were obtained, although the data were not smoothly\nsampled over the sampling period of about four days. We tentatively analyse the\namplitudes and time scales of the variabilities, and any possible periodicity.\nThe blazars vary significantly in the radio (except 3C66A and BL Lacertae with\nonly marginal variations) and optical bands on intra- and inter-day time\nscales, and the source B0925+504 exhibits a strong quasi-periodic radio\nvariability. No significant correlation between the radio- and optical-band\nvariability appears in the five sources, which we attribute to the radio IDV\nbeing dominated by interstellar scintillation whereas the optical variability\ncomes from the source itself. However, the radio- and optical-band variations\nappear to be weakly correlated in some sources and should be investigated based\non well-sampled data from future observations.\n