Spectral properties of 441 radio pulsars

Abstract

We present a study of the spectral properties of 441 pulsars observed with the Parkes radio telescope near the centre frequencies of 728, 1382 and 3100 MHz. The observations at 728 and 3100 MHz were conducted simultaneously using the dual-band 10-50cm receiver. These high-sensitivity, multi-frequency observations provide a systematic and uniform sample of pulsar flux densities. We combine our measurements with spectral data from the literature in order to derive the spectral properties of these pulsars. Using techniques from robust regression and information theory we classify the observed spectra in an objective, robust and unbiased way into five morphological classes: simple or broken power law, power law with either low or high-frequency cutoff and log-parabolic spectrum. While about 79% of the pulsars that could be classified have simple power law spectra, we find significant deviations in 73 pulsars, 35 of which have curved spectra, 25 with a spectral break and 10 with a low-frequency turn-over. We identify 11 gigahertz-peaked spectrum (GPS) pulsars, with 3 newly identified in this work and 8 confirmations of known GPS pulsars; 3 others show tentative evidence of GPS, but require further low-frequency measurements to support this classification. The weighted mean spectral index of all pulsars with simple power law spectra is −1.60 ± 0.03. The observed spectral indices are well described by a shifted log-normal distribution. The strongest correlations of spectral index are with spin-down luminosity, magnetic field at the light-cylinder and spin-down rate. We also investigate the physical origin of the observed spectral features and determine emission altitudes for three pulsars.

Limits on absorption from a 332-MHz survey for fast radio bursts

“…We scaled the obtained 1.4-GHz flux density to 332 MHz and applied reduction to the peak flux due to scattering and the correction due to free-free absorption and ICS in the rest frame of the source for a set of model parameters. For the flux scaling, we used a spectral index that was drawn from a normal distribution with a mean of −1.8 and unity variance (Jankowski et al 2018). Finally, we obtained the final peak fluxes at 332 MHz for our N simulated events in the observer's frame and ran a simulated search, accounting for the reduction in sensitivity due to channel flagging and RFI over the resulting events.…”

Gigahertz-peaked spectra pulsars in Pulsar Wind Nebulae

“…In case of PSR J1718−3825 the source was not detected at 325 MHz (only upper limit established) and there were only three measurements for fitting the three parameter model. We assumed an intrinsic spectral index α = −1.6, which is the average spectral index in the pulsar population (Lorimer et al 1995;Maron et al 2000;Jankowski et al 2017), and estimated the other parameters as shown in Table 3. In Kijak et al (2017) the spectral nature of the pulsar J1809−1917 was estimated using only high frequency measurements (> 1 GHz).…”

“…The radio emission from pulsars are characterized by a steep power law spectrum with typical spectral index around −1.6 (Lorimer et al 1995;Maron et al 2000;Jankowski et al 2017) over a wide frequency range from 0.1 -10 GHz. A new spectral type in radio pulsars was identified by Kijak et al (2007) where the pulsar spectra were observed to show a turn over around gigahertz frequencies.…”

“…These sources are called gigahertz-peaked spectrum (GPS) pulsars and only a handful of such sources are known. A systematic search for GPS pulsars have been conducted since the initial discovery (Kijak et al 2011a(Kijak et al ,b, 2013Dembska et al 2014Dembska et al , 2015aBasu et al 2016;Kijak et al 2017;Jankowski et al 2017) with seventeen pulsars confirmed to exhibit GPS behaviour. The GPS pulsars are usually associated with young energetic sources which are found in peculiar environments like Pulsar wind nebulae (PWN), HII regions, Supernova remnants (SNR), etc.…”

The emission and scintillation properties of RRAT J2325−0530 at 154 MHz and 1.4 GHz

“…The mean spectral index is α = −2.2 ± 0.1 with a standard deviation of σ = 0.4 ± 0.1. The grey shaded region is the typical distribution of spectral indices, with a mean of α = −1.6 and standard deviation of σ = 0.5(Jankowski et al, 2018). servations in the past from the GBT (350 MHz), LOFAR (150 MHz) and LWA1 (30-80 MHz).…”