RADIO PHYSICS AND RADIO ASTRONOMY

PACS numbers: 95.75.Wx,
95.85.Bh

Purpose: From April 2017, a monitoring program of observations has been started at the RT-16 telescope of Ventspils Radio Astronomy Center (frequencies 5, 6.1, 6.7, 8.4 GHz) to study the intraday and interdiurnal variability of extragalactic radio sources. At the first stage, the technique was developed and trial observations of extragalactic radio sources 3C 295, 3C 273, 3C 454.3, BL Lac and OJ 287 were made.

Design/methodology/approach: Research efforts were made to test the modes of source observations in the context of some other different programs and calibration procedures, taking into account the influence of various factors in monitoring observations with the RT-16. For this type of data, the most effective is search for quasiperiods of radio source fluxes by the Lomb–Scargle method with the following approximation of observations by trigonometric polynomials.

Findings: The radio source 3C 295 appears to have quasiperiodic fluctuations in radiant flux density at the time scale of ≈4 h, as well as  ≈ 5 and 7 h in different observation sessions, and long-term oscillations at the time scale of 10÷11 and 3÷4 days. In radio sources 3C 273 and 3C 454.3, due to a small number of observations, only the day-to-day trends are observed, BL Lac and OJ 287 show no trend and quasi-periodic changes in flux density. Obtained results are preliminary and will be refined with accumulation of observational data.

Conclusions: Methodology for realization of observations and calibration was prepared and tested for the monitoring program to study intraday and interdiurnal variability of extragalactic radio sources using the RT-16 telescope of Ventspils Radio Astronomy Center. Preliminary results of analysis of obtained data showed the effectiveness of applied technique and their conformity to the results of similar studies published earlier.

Key words: radio telescope, radio source, periodogram, quasiperiodic changes, intraday variability, trigonometric polynomial  

 Radio phys. radio astron. 2017, 22(4): 256-269

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