J. Kijak

Pulsars with gigahertz-peaked spectra

Aims: We investigate a high frequency turn-over effect in radio spectra for pulsars with positive or flat spectral index. Methods. Using GMRT and Effelsberg observatory, we estimated the flux density to reconstruct pulsar spectra. Results. We find objects that have a maximum flux in their spectrum above 1 GHz, whose emitted energy decreases below 1 GHz and whose spectral indices are positive at lower frequencies. Some pulsars with a turn-over in their spectrum at high frequencies are found to exist in very interesting environments. We call these objects gigahertz-peaked spectra pulsars.

Pulse broadening analysis for several new pulsars and anomalous scattering

ABSTRACT We show the results of our analysis of the pulse broadening phenomenon in 25 pulsars at sev-eral frequencies using the data gathered with GMRT and Effelsberg radiotelescopes. Twentytwo of these pulsars were not studied in that regard before and our work has increased thetotal number of pulsars with multi-frequency scattering measurements to almost 50, basi-cally doubling the amount available so far. The majority of the pulsars we observed havehigh to very-high dispersion measures (DM > 200) and our results confirm the suggestion ofLo¨hmer et al. (2001, 2004) that the scatter time spectral indices for high-DM pulsars deviatefrom the value predicted by a single thin screen model with Kolmogorov’s distribution of thedensity fluctuations. In this paper we discuss the possible e xplanations for such deviations.Key words: stars: pulsars – general, pulsars – scattering 1 INTRODUCTIONThe existence of the ionized fraction of the Interstellar Medium(ISM) affects the incoming pulsar radiation in several ways. Thefirst order e ffect - the interstellar dispersion - is due to the amountof the free electrons along the line-of-sight, usually quantized bythe Dispersion Measure: DM =R

Turn-over in pulsar spectra around 1 GHz

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 analysis of the largest sample of multifrequency pulsar scatter time estimates

We present our results of pulse broadening time estimates and the study of the frequency scaling of this quantity for 60 pulsars based on actual multi-frequency scattering estimates. This research was based on our own measurements, performed on the observational data and the profiles from various pulsar profile databases, as well as the scatter time measurements that were found in the literature. We were able to construct a database of over 60 pulsars with true multi-frequency

Flux-density spectral analysis for several pulsars and two newly identified gigahertz-peaked spectra pulsars

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On the aberration–retardation effects in pulsars

measurements, which allowed us to revise the previously proposed relations between the scatter time spectral slope and the dispersion measure (DM). We found that the deviations from theoretical predictions of the value of

THERMAL ABSORPTION AS THE CAUSE OF GIGAHERTZ-PEAKED SPECTRA IN PULSARS AND MAGNETARS

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Spectrum evolution in binary pulsar B1259−63/LS 2883 Be star and gigahertz‐peaked spectra

appear for pulsars regardless of their DM, however the DM-averaged value of the scaling index is almost constant except for pulsars with very high DMs. Based on the obtained slopes we were also able to estimate the amount of scattering at the standard frequency of 1 GHz. We found that while the estimated standardized pulse broadening time increases with DM the relation seems to be much flatter than it was previously proposed, which suggests higher values of the scatter time for mid-DM pulsars, and lower values of expected pulse broadening for highly dispersed sources.

Frequency Dependence of Pulsar Radiation Patterns

In this paper, we present results from flux-density measurements for 21 pulsars over a wide frequency range, using the Giant Metrewave Radio Telescope (GMRT) and the Effelsberg telescope. Our sample was a set of mostly newly discovered pulsars from the selection of candidates for gigahertz-peaked spectra (GPS) pulsars. Using the results of our observations along with previously published data, we identify two new GPS pulsars. One of them, PSR J1740+1000, with dispersion measure (DM) of 24 pc cm

Flux density measurements of gigahertz-peaked spectra candidate pulsars at 610 MHz using an interferometric imaging technique

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