Paper detail

Intranight variability of ultraviolet emission from high-$z$ blazars

Rapid intranight variability of continuum and polarization in blazars is a very useful tool to probe the beaming of a relativistic jet and the associated population of the relativistic particles. Such intranight variability in the rest-frame optical continuum has been carried out extensively, but there is a scarcity of such information in the rest-frame ultra-violet (UV), where the cause of variability might be due to {a} secondary population of relativistic particles. To fill this gap, recently in Chand et al. (2022) we reported for the first time intranight variability study of a sample of high-$z$ blazars so that the monitored optical radiation is their rest-frame UV radiation. Here we discuss in detail the implication of this investigation with a proper comparison of high-$z$ blazar samples with fractional optical polarization ($p_{opt}$) smaller and higher than 3\%. In this context, we also report intranight variability study of an additional high-$z$ blazar at $z$=2.347, namely J161942.38+525613.41, monitored over three sessions each with a duration of $\sim$5 hr. Our investigation does not reveal any compelling evidence for a stronger intranight variability of UV emission for high polarization blazars, in contrast to the blazars monitored in the rest-frame blue-optical. We also discuss this trend in light of the proposal that the synchrotron radiation of blazar jets in the UV/X-ray regime may arise from a relativistic particle population different from that radiating up to near-infrared/optical frequencies.