Flux Densities, Spectra and Variability of Pulsars at Metre Wavelengths

Abstract

We present the results of two-frequency flux density measurements of 74 pulsars with the Culgoora circular array. We show that the spectral index of a typical pulsar steepens markedly from 80 to 1400 MHz, but we found no significant relationship between the metre-wave spectral index and the published pulsar parameters.We investigated the intensity changes in 22 pulsars at 160 MHz over an l8-month interval and found that 19 of them were variable on a month-to-month time scale. A search for relationships between the degree of variability and the published pulsar parameters showed a highly significant dependence on dispersion measure and a probable dependence on period derivative. We attribute the dependence on dispersion measure to slow scintillations caused by large-scale turbulence in the interstellar medium, although the high amplitude of the intensity changes is not consistent with a recently proposed model for slow interstellar scintillation. The dependence of variability on period derivative and a high degree of correlation between intensity changes at 80 and 160 MHz demonstrate the presence of an intrinsic variability component.

Spectral indices for radio emission of 228 pulsars

“…We also compiled spectral indices of pulsars in the literature. Previously, spectral indices have been determined for 426 pulsars (Sieber, 1973;Kramer et al, 1998;Malofeev et al, 1994;Lorimer et al, 1995;Toscano et al, 1998;Kijak et al, 1998;Maron et al, 2000;Sieber et al, 1975;Izvekova et al, 1979;Kramer et al, 1999;Cordes, 1978;Dembska et al, 2014;Bates et al, 2011;Slee et al, 1986;Deneva et al, 2009;Foster et al, 1991;Hobbs et al, 2011;Joshi et al, 2009;Lambert & Rickett, 1999;Lommen et al, 2000;Lorimer & Xilouris, 2000;McLaughlin et al, 2002;Malofeev, 1996;Malofeev et al, 2000;Rankin et al, 1970;Robinson et al, 1968). In our sample, 28 pulsars have their spectral indices determined in the literature, and 200 weak pulsars have newly determined spectral indices.…”

Pulse shapes of radio pulsars at 4.85 GHz

“…We have combined the data from this survey with other published flux measurements in the frequency range Slee et al 1986) between 1.41 GHz and 4.85 GHz. Figure 4 shows the distribution of spectral indices for all pulsars in the combined sample.…”

Observing pulsars and fast transients with LOFAR

“…Though radio pulsars form over 85% of the known neutron star population, they are generally very weak radio sources with pulsed flux densities ranging from 0.0001 to 5 Jy with a median of 0.01 Jy at a frequency of 400 MHz. The pulsed flux density at radio wavelengths exhibits a steep spectrum (S ∝ ν α ; −4 < α < 0; α mean = −1.8, Maron et al 2000) that often peaks and turns over at frequencies between 100 and 200 MHz (Kuzmin et al 1978;Slee et al 1986;Malofeev et al 1994). …”