Search for Pulsars with Periods of More Than Two Seconds at Declinations from +21° to +42°

Abstract

The search for long period transients with periods (\(P\)) from 2 to 90 s was carried out in daily observations conducted in an area of 6300 sq. deg. The data was obtained using a Large Phased Array (LPA) at a frequency of 111 MHz. Periodograms calculated using the Fast Folding Algorithm (FFA) were used for the search. To increase the sensitivity, the periodograms obtained in different observation sessions were added. Of the 14 known pulsars that entered the study area, having periods of \(P > 2\) s and dispersion measures (\(DM\)) less than 200 pc/cm³, nine were detected. Two new pulsars were found. The average profiles of pulsars are obtained and estimates of their flux density are given. Discovered pulsar J1951+28 with a period of \(P = 7.3342\) s and \(DM\) = 3.5 pc/cm³ turned out to be one of the closest pulsars to the Sun. The absence of new long period transients (pulsars or white dwarf) with periods of tens of seconds with the achieved sensitivity of searching for 1 mJy outside the galactic plane indicates a low probability of the existence of pulsars of neutron stars with extremely long periods. Most likely, the recently found sources of periodic radiation with periods from a minute to tens of minutes are white dwarfs pulsars.