2018RAA....18...96V

Since 2013, round-the-clock monitoring of the sky has been carried out simultaneously in 96 beams using a high-sensitivity radio telescope called the Large Phased Array (LPA) at the frequency 110.25 MHz. These observations are made under the program of interplanetary plasma investigation. The same data are used to search for pulsars by means of power spectra. To increase the sensitivity of the pulsar search, 500-600 power spectra corresponding to different days of observations are summed. In the integrated spectra of known pulsars, besides expected improvement in signal-to-noise (S/N) ratio for the frequency harmonics, some features are explored in this paper. We present the 27 strongest pulsars which are in a field with declination 21° - 42°. The observable details in the integrated power spectra are connected with the presence of pulsar periods of the second (P₂) and third (P₃) class, which have been identified. Empirical relations for calculating these periods are obtained. The value P₂ is estimated for 26 pulsars, and for 15 sources it is made for the first time. The value P₃ is estimated for 13 pulsars, among them these values are given for five sources for the first time.