S. A. Tyul’bashev

Search for and detection of pulsars inmonitoring observations at 111 MHz

In the course of monitoring interplanetary scintillations of a large number of sources using the Big Scanning Antenna of the Lebedev Physical Institute, a search for pulsars with periods ≥0.4 s at declinations −9◦ < δ < 42◦ and right ascensions 0h < α < 24h was simultaneously carried out. The search was conducted using four years of observations carried out at 110.25MHz in six frequency channels making up a 2.5 MHz band and having a time resolution of 100 ms. The initial identification of pulsar candidates was done using Fourier power spectra averaged over the entire observational period; the pulsar candidates were then verified using observations with higher frequency and time resolution: 32 frequency channels and a time resolution of 12.5 ms. Eighteen new pulsars were discovered in the studied area, whose main characteristics are presented.

Relative variations of the physical parameters of variable extragalactic radio sources

A method for studying the physical conditions in compact components of extragalactic radio sources displaying variability on time scales of hundreds of days is proposed. The method can be used to estimate the relative variations of the magnetic-field strength and number density of relativistic electrons in superluminal jets from the cores of quasars and radio galaxies. Results are presented for the jets of the quasars 3C 120, 3C 273, 3C 279, and 3C 345. The energies of the magnetic field and relativistic particles in these objects are not in equipartition. As a rule, the magnetic-field strength decreases appreciably during the evolution of an expanding jet, while the number of relativistic electrons grows.

Detection of Five New RRATs at 111 MHz

Results of 111-MHz monitoring observations carried out on the Big Scanning Antenna of the Pushchino Radio Astronomy Observatory during September 1–28, 2015 are presented. Fifty-four pulsating sources were detected at declinations −9° < δ < 42°. Forty-seven of these are known pulsars, five are new sources, and two are previously discovered transients. Estimates of the peak flux densities and dispersion measures are presented for all these sources.

The magnetic fields and density of relativistic electrons in the nucleus of NGC 1052

We analyze observations of the compact GHZ-peaked-spectrum radio source in the nucleus of the weakly active galaxy NGC 1052, assuming that the low-frequency turnover in its spectrum is due to synchrotron self-absorption. The analysis is based on a model for an inhomogeneous source of synchrotron radiation. It is shown that the magnetic field is not uniform, but the change in the field strength from the center to the edge of the compact radio source does not exceed an order of magnitude. The maximum magnetic-field strength in the nucleus of NGC 1052 is 20 G < H⊥ < 200 G, and the density of relativistic electrons is 0.018 cm−3 < ne < 0.18 cm−3 on scales of 0.1 pc; everywhere in the radio source, the energy density of the magnetic field exceeds the energy density of the relativistic electrons. The physical conditions are similar to those in the nuclei of the nearby radio galaxies 3C 111 and 3C 465, and differ strongly from those in the nucleus of the radio galaxy 0108+388, which is a compact GHz-peaked-spectrum source (these three galaxies were studied by the authors earlier using the same method).

The asymmetry coefficient for interstellar scintillation of extragalactic radio sources

Comparing the asymmetry coefficients γ and scintillation indices m for observed time variations of the intensity of the radiation of extragalactic sources and the predictions of theoretical models is a good test of the nature of the observed variations. Such comparisons can be used to determine whether flux density variations are due to scintillation in the interstellar medium or are intrinsic to the source. In the former case, they can be used to estimate the fraction of the total flux contributed by the compact component (core) whose flux density variations are caused by inhomogeneities in the interstellar plasma. Results for the radio sources PKS 0405-385, B0917+624, PKS 1257-336, and J1819+3845 demonstrate that the scintillating component in these objects makes up from 50 to 100% of the total flux, and that the intrinsic angular sizes of the sources at 5 GHz are 10–40 microarcseconds. The characteristics of the medium giving rise to the scintillations are presented.

Detection of 25 new rotating radio transients at 111 MHz

Nearly all fast radio RRAT-type transients that are pulsars with rare pulses have been previously detected using decimetre wavelengths. We present here 34 transients detected at metre wavelengths in our daily monitoring at declinations -9o < decl. < +42o. 25 transients are new RRATs. We confirmed the detection of 7 RRATs based on our early observations. One of the 34 detected transients was determined to be a new pulsar J1326+3346. At the same time, out of 35 RRATs detected at the decimetre wavelengths and included in the studied area, only one was detected by us J1848+1518. The periods of 6 RRATs were found from the time of arrival of single pulses. Three quarters of all RRATs were observed more than once and the total number of RRATs in the area studied has doubled.

A method for determining redshifts from radio data

The possibility of estimating the redshifts of radio sources based on radio continuum observations is demonstrated. Since the pressure exerted on the intergalactic medium by radio lobes is associated only with their total energy, while the pressure exerted on the radio lobes by the intergalactic medium depends on the redshift, the redshift can be estimated. The proposed method does not require the use of standard candles or standard sizes for any features. Consequently, it is free of the influence of cosmological evolution of the radio sources. Our insufficient knowledge of the density and temperature of the intergalactic medium prevents us from applying the method to obtain direct estimates of the distances to extragalactic radio sources. Therefore, a method designed to enable indirect estimation of the source distances has also been developed.