Observations within the Framework of SETI Program on RATAN-600 Telescope in 2015 and 2016

In 2015–2016 regular observations within the SETI program were carried out at the RATAN-600 radio telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The aim of observations was to search for artificial signals from about 30 Sun-like stars and two metal-rich globular clusters. The main underlying idea of these studies was to perform multiple repeated observations (monitoring) of the same objects. The data were analyzed using three methods: we (1) searched for a strong single signal, (2) estimated the flux averaged over the entire observing time, and (3) analyzed the correlations between signals at different frequencies. Collecting the data over two observing years made it possible to perform a search for weak signals at the detection level of several mJy at 2.7 and 6.3 cm wavelengths. The power limits on the signals of extraterrestrial civilizations averaged over the entire data set lie in the 1016–1020 Winterval practically for all objects, whereas the upper luminosity limits for single observations (the beam crossing time was 7–19 s) are 1017–1021 W and the effective isotropic emitted power of the hypothetical transmitters of the said civilizations do not exceed 2 × 109–2 × 1013 W, which is close to the corresponding parameter for the biggest planetary radars. The resulting luminosity limits are indicative of the absence of radio emission from the observed Sun-like stars, which is stationary on average and exhibits flare-like behavior during some observing sessions.