DJp.2.26 — Multi-colour High Time-resolution Simultaneous Photometric Studies of Blazars

Date & Time

Aug 10th at 6:00 PM until 6:00 PM




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Author(s): Meng Zhai1

Institution(s): 1. NAOC

Blazars are a subclass of active galactic nuclei (AGNs), whose nature remains unclear. They consist of BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs) that are typically sources with highly variable and polarized non-thermal continuum emission ranging from radio up to X-ray and often to γ-ray frequencies. The intraday variability (IDV) of blazars has been established for some time. Although the mechanism(s) of IDV in all AGNs remains inconclusive, for blazars it is commonly related to the non-thermal Doppler-boosted emission from jets. The shock-in-jet model suggests that the relativistic particle jets cause the IDV phenomenon even on the timescales of less than one hour.
Simultaneous multiband photometric observations help to guarantee that the detected emissions are emitted at the same time from various zones of the source. This could also help us to explain our data and perhaps constrain mechanism parameters, because it is possible to make unambiguous estimates about the variability mechanisms based on the light curve shapes and timescales. To further study the blazars’ multiband variability, colour behaviour, and the correlations among flux variations in different wavelengths, there is a need to collect data over relatively long observing periods to monitor multiband variability.
The observations would carried out using both the 1 m telescope and the 0.8 m telescope simultaneously in most nights at the Xinglong Observatory of NAOC. Both telescopes are quipped with the same type of CCD and standard Johnson-Cousin UBVRI filters. To reach a similar signal-to-noise ratio (S/N) in different bands with the same exposure time, observations using the larger diameter 1 m telescope are carried out with B-band filter, while those of the smaller diamter 0.8 m telescope are carried out with R-band filter. Any time differences between the two telescopes are corrected using GPS. The typical sampling rate is one data point per minute, which is the highest time-resolution so far. The synchronized use of two or more telescopes could greatly improve the temporal resolution to help us monitor the outbursts of the blazars.