90-Thorium

Malov, L.A.

doi:10.1007/10667325_31

Cited by 2 publications

(2 citation statements)

References 15 publications

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“…Efforts to measure the radio spectra of a large number of pulsars began in earnest with Sieber (1973), followed by Malofeev & Malov (1980) and Izvekova et al (1981) at low frequencies near 100 MHz and below. It was found that the majority of pulsars have steep spectra that can be described using a simple power law with spectral index α.…”

Section: Introductionmentioning

confidence: 99%

Spectral properties of 441 radio pulsars

Jankowski

Straten

Keane

et al. 2017

Monthly Notices of the Royal Astronomical Society

206

185

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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.

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Section: Introductionmentioning

confidence: 99%

Spectral properties of 441 radio pulsars

Jankowski

Straten

Keane

et al. 2017

Monthly Notices of the Royal Astronomical Society

206

185

View full text Add to dashboard Cite

show abstract

“…Despite these difficulties, anomalous X-ray pulsars have been studied at 102-111 MHz (Malov & Malofeev 2010;Malov 2014), and a large sample of pulsar light curves have been studied over a broad range of frequencies by LOFAR (Bilous et al 2016;Kondratiev et al 2016), down to as low as 15 MHz (Pilia et al 2016). Generally, a low-frequency turnover in the spectrum of radio pulsars is associated with a corresponding evolution of the pulse profile, related to processes occurring near the rest-frame plasma frequency above the polar cap (Sieber 1970;Malofeev & Malov 1980). While many NSs do not show evidence of such a turnover (Bilous et al 2016;Kondratiev et al 2016), this feature has been identified in a number of objects.…”

Section: Discussionmentioning

confidence: 99%

Escape and trapping of low-frequency gravitationally lensed rays by compact objects within plasma

Rogers

2016

Mon. Not. R. Astron. Soc.

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We consider the gravitational lensing of rays emitted by a compact object (CO) within a distribution of plasma with power-law density ∝ r −h . For the simplest case of a cloud of spherically symmetric cold non-magnetized plasma, the diverging effect of the plasma and the converging effect of gravitational lensing compete with one another. When h < 2, the plasma effect dominates over the vacuum Schwarzschild curvature, potentially shifting the radius of the unstable circular photon orbit outside the surface of the CO. When this occurs, we define two relatively narrow radio-frequency bands in which plasma effects are particularly significant. Rays in the escape window have ω 0 < ω ω + and are free to propagate to infinity from the CO surface. To a distant observer, the visible portion of the CO surface appears to shrink as the observed frequency is reduced, and vanishes entirely at ω 0 , in excess of the plasma frequency at the CO surface. We define the anomalous propagation window for frequencies ω − < ω ω 0 . Rays emitted from the CO surface within this frequency range are dominated by optical effects from the plasma and curve back to the surface of the CO, effectively cloaking the star from distant observers. We conclude with a study of neutron star (NS) compactness ratios for a variety of nuclear matter equations of state (EoS). For h = 1, NSs generated from stiff EoS should display significant frequency dependence in the EW, and lower values of h with softer EoS can also show these effects.

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90-Thorium

Cited by 2 publications

References 15 publications

Spectral properties of 441 radio pulsars

Spectral properties of 441 radio pulsars

Escape and trapping of low-frequency gravitationally lensed rays by compact objects within plasma

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