Abstract
We reviewed multi-wavelength blazars variability and detection of quasi-periodic oscillations on intra-day timescales. The variability timescale from few minutes to up to less than a days is commonly known as intra-day variability. These fast variations are extremely useful to constrain the size of emitting region, black hole mass estimation, etc. It is noticed that in general blazars show intra-day variability in the complete electromagnetic spectrum. But some class of blazars either do not show or show very little intra-day variability in a specific band of electromagnetic spectrum. Blazars show rarely quasi-periodic oscillations in time series data in optical and X-ray bands. Other properties and emission mechanism of blazars are also briefly discussed.
Highlights
It is commonly accepted that super massive black holes (SMBHs, with masses between and 1010 M [1]) are present in the nuclei of all galaxies with stellar bulges
It has been proposed that different types of AGNs can be explained by the idea that different line of sight (LOS) angles can play an important role in understanding their different properties [2,3]
For Mrk 421, we found that shortest intra-day variability (IDV) timescale ≈2.4 ks, δ = 25, B > 0.26 ν18
Summary
It is commonly accepted that super massive black holes (SMBHs, with masses between and 1010 M [1]) are present in the nuclei of all galaxies with stellar bulges. A few percent of these SMBHs are fed with a sufficient amount of gas that they will possess significant accretion discs The emission of these discs is comparable to the total emission of stars in the entire host galaxy because of a very high efficiency for the conversion of matter into radiation as it spirals into a BH. The high-energy component of the spectral energy distribution (SED) of blazars extends up to γ-rays, peaking at GeV energies in LSPs and at TeV energies in HSPs. Blazar properties are consistent with relativistic beaming, i.e., bulk relativistic motion of the jet plasma at small angles to the line of sight, which gives rise to a strong amplification and rapid variability in the observer’s frame. Simultaneous multi-wavelength observations of blazars in the entire EM spectrum are an important tool to test several possible models for IDV: shock-in-jet models, accretion-disk-based models, models based on plasma instabilities in shear layers, etc
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