The study of multi-frequency scattering of 10 radio pulsars

Abstract

We present the results of the multi-frequency scatter time measurements for ten radio pulsars that were relatively less studied in this regard. The observations were performed using the Giant Meterwave Radio Telescope at the observing frequencies of 150, 235, 325, 610 and 1060 MHz. The data we collected, in conjunction with the results from other frequencies published earlier, allowed us to estimate the scatter time frequency scaling indices for eight of these sources. For PSR J1852−0635 it occurred that its profile undergoes a strong evolution with frequency, which makes the scatter time measurements difficult to perform, and for PSR J1835−1020 we were able to obtain reliable pulse broadening estimates at only two frequencies. We used the eight frequency scaling indices to estimate both: the electron density fluctuation strengths along the respective lines-of-sight, and the standardized amount of scattering at the frequency of 1 GHz. Combining the new data with the results published earlier by Lewandowski et al., we revisited the scaling index versus the dispersion measure (DM) relation, and similarly to some of the earlier studies -we show that the average value of the scaling index deviates from the theoretical predictions for large DM pulsars, however it reaches the magnitude claimed by Löhmer et al. only for pulsars with very large DMs (>650 pc cm −3 ). We also investigated the dependence of the scattering strength indicators on the pulsar distance, DM, and the position of the source in the Milky Way Galaxy.

Evidence for magnetospheric effects on the radiation of radio pulsars

“…Several authors (e.g. Lewandowski et al 2015b;Noutsos et al 2015) observed this pulsar to be scattered at low frequencies. Hence it is possible that the observed RM variations were caused by low level scattering.…”

A New Electron-Density Model for Estimation of Pulsar and FRB Distances

“…Numerous observations (e.g., Stinebring 2006;Trang & Rickett 2007;Brisken et al 2010) have shown that interstellar scattering is typically dominated by just a few regions of very strong n e fluctuations along the path to a pulsar. This makes it essentially impossible to satisfactorily model the large-scale distribution of interstellar scattering and leads to the very large scatter seen in plots of SM and scattering delay t sc versus DM (e.g., Krishnakumar et al 2015;Lewandowski et al 2015).…”

Scattering features and variability of the Crab pulsar

“…A thin-screen scattering model is an approximation that assumes that the material causing the pulse scatter-broadening is in a thin screen between the observer and the object (Williamson 1972). The screen is usually attributed to the ISM and it is expected that −4.4 < α < −4 (Lewandowski et al 2015); where α = −4.4 assumes a Kolmogorov spectrum (Kuzmin et al 2002) and α = −4 assumes Gaussian inhomogeneities (Lang 1971;Lee & Jokipii 1976), however many pulsars have been observed to have α values greater than −4 and less than −4.4 (Krishnakumar et al 2017). The frequency dependence of pulse scatter-broadening is shown in Fig.…”