A LOFAR census of non-recycled pulsars: average profiles, dispersion measures, flux densities, and spectra

Abstract

We present first results from a LOFAR census of non-recycled pulsars. The census includes almost all such pulsars known (194 sources) at declinations Dec > 8• and Galactic latitudes |Gb| > 3• , regardless of their expected flux densities and scattering times. Each pulsar was observed for ≥20 min in the contiguous frequency range of 110-188 MHz. Full-Stokes data were recorded. We present the dispersion measures, flux densities, and calibrated total intensity profiles for the 158 pulsars detected in the sample. The median uncertainty in census dispersion measures (1.5 × 10 −3 pc cm −3 ) is ten times smaller, on average, than in the ATNF pulsar catalogue. We combined census flux densities with those in the literature and fitted the resulting broadband spectra with single or broken power-law functions. For 48 census pulsars such fits are being published for the first time. Typically, the choice between single and broken power-laws, as well as the location of the spectral break, were highly influenced by the spectral coverage of the available flux density measurements. In particular, the inclusion of measurements below 100 MHz appears essential for investigating the lowfrequency turnover in the spectra for most of the census pulsars. For several pulsars, we compared the spectral indices from different works and found the typical spread of values to be within 0.5-1.5, suggesting a prevailing underestimation of spectral index errors in the literature. The census observations yielded some unexpected individual source results, as we describe in the paper. Lastly, we will provide this unique sample of wide-band, low-frequency pulse profiles via the European Pulsar Network Database.

The frequency dependence of scattering imprints on pulsar observations

“…Recent works showing average pulse profiles in the LO-FAR bands confirm the expectation of scatter broadened pulse shapes at these frequencies (Bilous et al 2015;Pilia et al 2015).…”

TMRT Observations of 26 Pulsars at 8.6 GHz

“…This is another of the original four pulsars discovered at Cambridge (Pilkington et al 1968) that has a classic two-component profile and has been studied at many different frequencies. At low radio frequencies, the two components are of comparable amplitude (Bilous et al 2016) but, as Fig. 1 shows, at 8.6 GHz, the trailing component is much weaker, indicating a much steeper spectrum.…”

Simultaneous radio and X-ray observations of PSR B0611+22

“…error on system parameters, beam jitter due to the propagation in the ionosphere or strong sources contributing through the side lobes of the beam. Detailed discussion on error calculation is provided by Bilous et al (2015).…”