We have conducted the Meterwavelength Single-pulse Polarimetric Emission Survey to study the radio emission properties of normal pulsars. A total of 123 pulsars with periods between 0.1 seconds and 8.5 seconds were observed in the survey at two different frequencies, 105 profiles at 333 MHz, 118 profiles at 618 MHz and 100 pulsars at both. In this work we concentrate primarily on the time-averaged properties of the pulsar emission. The measured widths of the pulsar profiles in our sample usually exhibit the radius to frequency mapping. We validate the existence of lower bounds for the distribution of profile widths with pulsar period (P ), which is seen for multiple definitions of the width, viz. a lower boundary line (LBL) at 2.7 • P −0.5 with width measured at 50% level of profile peak, a LBL at 5.7 • P −0.5 for 10% level of peak and LBL at 6.3 • P −0.5 for width defined as 5σ above the baseline level. In addition we have measured the degree of linear polarization in the average profile of pulsars and confirmed their dependence on pulsar spindown energy loss (Ė). The single pulse polarization data show interesting trends with the polarization position angle (PPA) distribution exhibiting the simple rotating vector model for highĖ pulsars while the PPA becomes more complex for medium and lowĖ pulsars. The single pulse total intensity data is useful for studying a number of emission properties from pulsars like subpulse drifting, nulling and mode changing which is being explored in separate works.

We study the mid-egress eclipse timing data gathered for the cataclysmic binary HU Aquarii during the years 1993-2014. The (O-C) residuals were previously attributed to a single ∼ 7 Jupiter mass companion in ∼ 5 au orbit or to a stable 2-planet system with an unconstrained outermost orbit. We present 22 new observations gathered between June, 2011 and July, 2014 with four instruments around the world. They reveal a systematic deviation of ∼ 60-120 seconds from the older ephemeris. We re-analyse the whole set of the timing data available. Our results provide an erratum to the previous HU Aqr planetary models, indicating that the hypothesis for a third and fourth body in this system is uncertain. The dynamical stability criterion and a particular geometry of orbits rule out coplanar 2-planet configurations. A putative HU Aqr planetary system may be more complex, e.g., highly non-coplanar. Indeed, we found examples of 3-planet configurations with the middle planet in a retrograde orbit, which are stable for at least 1 Gyr, and consistent with the observations. The (O-C) may be also driven by oscillations of the gravitational quadrupole moment of the secondary, as predicted by the Lanza et al. modification of the Applegate mechanism. Further systematic, long-term monitoring of HU Aqr is required to interpret the (O-C) residuals.

Aims. The main aim is to investigate the possibility of a high frequency turn-over in the radio spectrum of pulsars. Methods. Using the GMRT, multi-frequency flux density measurements of several candidate pulsars have been carried out and their spectra have been extended to lower frequencies. Results. We present the first direct evidence for turn-over in pulsar radio spectra at high frequencies. A total of 3 pulsars (including 2 new ones from this study) are now shown to have a turn-over frequency > ∼ 1 GHz, and one is shown to have a turn-over at ∼600 MHz.

The magnetospheric locations of pulsar radio emission region are not well known. The actual form of the so-called radius-to-frequency mapping should be reflected in the aberrationretardation (A/R) effects that shift and/or delay the photons depending on the emission height in the magnetosphere. Recent studies suggest that in a handful of pulsars the A/R effect can be discerned with respect to the peak of the central core emission region. To verify these effects in an ensemble of pulsars, we launched a project analysing multifrequency total intensity pulsar profiles obtained from the new observations from the Giant Meterwave Radio Telescope (GMRT), Arecibo Observatory (AO) and archival European Pulsar Network (EPN) data. For all these profiles, we measure the shift of the outer cone components with respect to the core component, which is necessary for establishing the A/R effect. Within our sample of 23 pulsars, seven show the A/R effects, 12 of them (doubtful cases) show a tendency towards this effect, while the remaining four are obvious counterexamples. The counterexamples and doubtful cases may arise from uncertainties in the determination of the location of the meridional plane and/or the core emission component. Hence, it appears that the A/R effects are likely to operate in most pulsars from our sample. We conclude that in cases where those effects are present the core emission has to originate below the conal emission region.

Aims. We present the results of flux density monitoring of PSR B0329+54 at the frequency of 4.8 GHz using the 32-m TCfA radiotelescope. The observations were conducted between 2002 and 2005. The main goal of the project was to find interstellar scintillation (ISS) parameters for the pulsar at the frequency at which it was never studied in detail. To achieve this, the 20 observing sessions consisted of 3-min integrations, which on average lasted 24 h. This gave us sufficient sensitivity to all types of flux density variations over a wide range of timescales. The character of the observations makes our project unique amongst other ISS oriented observing programs, at least at high frequency. Methods. Flux density time series obtained for each session were analysed using structure functions. For some of the individual sessions as well as for the general average structure function we were able to identify two distinctive timescales present, the timescales of diffractive and refractive scintillations. To the best of our knowledge, this is the first case when both scintillation timescales, t DISS = 42.7 min and t RISS = 305 min, were observed simultaneously in a uniform data set and estimated using the same method. Results. The obtained values of the ISS parameters combined with the data found in the literature allowed us to study the frequency dependence of these parameters over a wide range of observing frequencies, which is crucial for understanding the ISM turbulence. We found that the Kolmogorov spectrum is not best suited for describing the density fluctuations of the ISM, and a power-law spectrum with β = 4 seems to fit better with our results. We were also able to estimate the transition frequency (transition from strong to weak scintillation regimes) as ν c = 10.1 GHz, much higher than was previously predicted. We were also able to estimate the strength of scattering parameter u = 2.67 and the Fresnel scale as r F = 6.7 × 10 8 m.