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.Comment: 6 pages, 3 figures, 1 table; Astronomy and Astrophysics in pres

About the search for pulsed radiation from the magnetar SGR1935+2154 at the LPA LPI

J1935+2154 is known as a source of soft gamma radiation. Hyperflares from magnetar were detected at a frequency of 1.25 GHz on the FAST telescope in May 2020. The magnetar enters the survey conducted on LPA radio telescope at 111 MHz. A check of the previously published (Fedorova et al. 2021) pulse from the magnetar SGR1935+2154 was carried out. The data received on the LPA is recorded in parallel in two modes having low and high frequency-time resolution: 6 channels with a channel width of 415 kHz and a time resolution of \Delta t = 100 ms; 32 channels with a channel width of 78 kHz and a time resolution of \Delta t = 12.5 ms. The original search was carried out using data with low time-frequency resolution. The search for dispersed signals in the meter wavelength range is difficult, compared with the search in the decimeter range, due to scattering proportional to the fourth power of frequency and dispersion smearing of the pulse in frequency channels proportional to the second power of frequency. In order to collect a broadened pulse signal and obtain the best value of S/N, the search was carried out using an algorithm based on the convolution of multichannel data with a scattered pulse pattern. The shape of the template corresponds to the shape of a scattered pulse with a dispersion measure (DM) of 375 pc/cm3. For repeated verification, the same data was used in which the pulse from the magnetar was detected. An additional check of the published pulse was also carried out using data with a higher frequency-time resolution. Since the dispersion smearing in the frequency channel in the 32-channel data is 5 times less than in the 6-channel data, an increase approximately 2 times in the S/N pulse could be expected. Pulse radiation with S/N>4 having a pulse peak shift depending on DM from SGR1935+2154 was not detected in either 32-channel or 6-channel data.Comment: published in Transactions of Institute of Applied Astronomy of Russian Academy of Sciences (IAA RAS), translated by Yandex translator with correction of scientific lexis, 4 pages, 3 figure

Search for pulsars in an area with coordinates 3h < \alpha < 4h and +21o < \delta < +42o

On the Large Phased Array (LPA) of Lebedev Physics Institute (LPI), a search for pulsars outside the Galaxy plane was carried out in a 300 sq. deg area. The search with a sensitivity 5-10 times better than that of previously conducted surveys was at a frequency of 111 MHz. The search was carried out in the summed power spectra. With an accumulation equivalent to 100 hours of continuous observations for each point of the area, 5 known pulsars were detected with a signal-to-noise ratio (S/N) from 20 to 1300 in the first harmonic of the spectrum. Average profiles were obtained for the detected pulsars. Estimates of the peak and integral flux densities of the found pulsars are given for individual sessions and for the power spectra summarized over 5.5 years, obtained using the developed method based on measurements of the height of harmonics in the power spectrum. No new pulsars have been detected in the area. Apparently, when searching for pulsars in the area, we have approached the lower limit of the luminosity of the second pulsars. The completeness of the survey is at the level of 0.5 mJy.Comment: published in Astronomy Reports, translated by Yandex translator with correction of scientific lexis, 7 pages, 3 figures, 2 table

Detection Statistics of Pulse Signals at Declinations from +42o+42^o to +52o+52^o at the Frequency 111 MHz

A search for pulse signals was carried out in a new sky area included in the monitoring program for the search for pulsars and transients. Processing of several months data recorded in six frequency channels with a total bandwidth of 2.5 MHz showed that, on average, 4 pulses per hour are observed in each of the 24 connected stationary beams. Of these pulses, 18.3% are similar to those of pulsars. They are visible in one or two neighboring beams and have a pronounced dispersion shift, that is, they are recorded first at a high and then at a low frequency, which indicates the possible passage of the signal through the interstellar medium. Almost 68% of such detected pulses belong to six known pulsars with dispersion measures from 9 to 141 $pc/cm^3$, and almost all of the remaining pulses are either noise of an unknown nature or artifacts of the proposed pulse separation technique. An additional study of the selected array of 3650 obvious pulsar pulses revealed 13 pulses belonging to four rotating radio transients (RRATs). Their dispersion measures are in the range of 17-51 $pc/cm^3$. A search for regular (periodic) RRAT emission was carried out using power spectra summed over 121 days. Periodic radiation was not detected, but for two RRATs, upper estimates of the periods were obtained from measurements of the time intervals between pulses. The upper estimates of the integrated flux density of the detected RRATs are in the range 2-4 mJy at the frequency 111 MHz.Comment: published in Astronomy Report, translated by Yandex translator with correction of scientific lexis, 6 pages, 3 figures, 2 table

Study of Bright Compact Radio Sources of the Northern Hemisphere at the frequency of 111 MHz

The search for compact components of strong ($S_{int} \ge 5$ Jy at 102.5 MHz) discrete radio sources from the Pushchino catalogue was carried out using the method of interplanetary scintillation. A total of 3620 sources were examined, and 812 of them were found to compact (scintillating) components. Estimates of fluctuations of the flux density of these compact components were derived from the scintillation index ($m_{max}$) corresponding to an elongation of $25^o$. The angular size and compactness of 178 sources with compact components were estimated. Scintillation indices of sources corresponding to the compact component ($m_{max}$) and flux densities of compact components were determined. It was demonstrated that slow variations of the spatial distribution of interplanetary plasma, which are related to the 11-year cycle of solar activity, may exert a systematic influence on the estimates of angular sizes of sources. Coefficients compensating the deviation from the spherical symmetry of solar wind in the estimates of angular sizes were found using the coefficient of asymmetry of the statistical distribution of intensity fluctuations. The study of correlations between the parameters of sources in the sample revealed that the maximum value of the scintillation index decreases as the integrated flux increases, while the angular size has no marked dependence on the integrated flux.Comment: published in Astronomy Report, translated by Yandex translator with correction of scientific lexis, 16 pages, 6 figures, 3 table, appendi

Detection of two new RRATs at 111 MHz

A search for pulse signals in a area with declinations of +52\degr <\delta <+55\degr was carried out on the LPA LPI radio telescope. When processing ten months of observations recorded in six frequency channels with a channel width of 415 kHz and a total bandwidth of 2.5 MHz, 22 thousand events were found with a pronounced dispersion delay of signals over frequency channels, i.e. having signs of pulsar pulses. It turned out that the found pulses belong to four known pulsars and two new rotating radio transients (RRATs). An additional pulse search conducted in 32-channel data with a channel width of 78 kHz revealed 8 pulses for the transient J0249+52 and 7 pulses for the transient J0744+55. Periodic radiation of transients was not detected. The analysis of observations shows that the found RRATs are most likely pulsars with nullings, where the proportion of nulling is greater than 99.9\%.Comment: published in Astronomy Reports, translated by Yandex translator with correction of scientific lexis, 5 pages, 2 figures, 1 tabl

Revisiting Pushchino RRAT search using neural network

The search for rotating radio transients (RRAT) at declination from -9o to +42o was carried out in the semi-annual monitoring data obtained on the Large Phased Array (LPA) radio telescope at the frequency of 111 MHz. A neural network was used to search for candidates. 4 new RRATs were detected, having dispersion measures (DM) 5-16 pc/cm3. A comparison with an earlier RRAT search conducted using the same data shows that the neural network reduced the amount of interference by 80 times, down to 1.3% of the initial amount of interferences. The loss of real pulsar pulses does not exceed 6% of their total number.Comment: 7 pages, 2 figures, submitted to A&