We show the results of our analysis of the pulse broadening phenomenon in 25 pulsars at several frequencies using the data gathered with GMRT and Effelsberg radiotelescopes. Twenty two of these pulsars were not studied in that regard before and our w
ork has increased the total number of pulsars with multi-frequency scattering measurements to almost 50, basically doubling the amount available so far. The majority of the pulsars we observed have high to very-high dispersion measures (DM>200) and our results confirm the suggestion of Loehmer et al.(2001, 2004) that the scatter time spectral indices for high-DM pulsars deviate from the value predicted by a single thin screen model with Kolmogorovs distribution of the density fluctuations. In this paper we discuss the possible explanations for such deviations.
We studied the radio spectrum of PSR B1259-63 in an unique binary with Be star LS 2883 and showed that the shape of the spectrum depends on the orbital phase. We proposed a qualitative model which explains this evolution. We considered two mechanisms
that might influence the observed radio emission: free-free absorption and cyclotron resonance. Recently published results have revealed a new aspect in pulsar radio spectra. There were found objects with turnover at high frequencies in spectra, called gigahertz-peaked spectra (GPS) pulsars. Most of them adjoin such interesting environments as HII regions or compact pulsar wind nebulae (PWN). Thus, it is suggested that the turnover phenomenon is associated with the environment than being related intrinsically to the radio emission mechanism. Having noticed the apparent resemblance between the B1259-63 spectrum and the GPS, we suggest that the same mechanisms should be responsible for both cases. Therefore, the case of B1259-63 can be treated as a key factor to explain the GPS phenomenon observed for the solitary pulsars with interesting environments and also another types of spectra (e.g. with break).
