Multifrequency Observations of Radio Pulse Broadening and Constraints on Interstellar Electron Density Microstructure

By N. D. Ramesh Bhat, J. Cordes, F. Camilo, D. Nice, D. R. Lorimer. 2004

285 citations recorded by the source corpus.

We have made observations of 98 low Galactic latitude pulsars to measure pulse broadening caused by multipath propagation through the interstellar medium. Data were collected with the 305 m Arecibo telescope at four radio frequencies between 430 and 2380 MHz. We used a CLEAN-based algorithm to deconvolve interstellar pulse broadening from the measured pulse shapes. We employed two distinct pulse-broadening functions (PBFs): PBF1 is appropriate for a thin screen of scattering material between the Earth and a pulsar, while PBF2 is appropriate for scattering material uniformly distributed along the line of sight from the Earth to a pulsar. We found that some observations were better fitted by PBF1 and some by PBF2. Pulse-broadening times (τd) are derived from fits of PBFs to the data and are compared with the predictions of a smoothed model of the Galactic electron distribution. Several lines of sight show excess broadening, which we model as clumps of high-density scattering material. A global analysis of all available data finds that the pulse broadening scales with frequency, ν, as τd ∝ ν-α, where α ~ 3.9 ± 0.2. This is somewhat shallower than the value α = 4.4 expected from a Kolmogorov medium but could arise if the spectrum of turbulence has an inner cutoff at ~300-800 km. A few objects follow particularly shallow scaling laws (the mean scaling index ⟨α⟩ ~ 3.1 ± 0.1 and ~3.8 ± 0.2, respectively, for PBF1 and PBF2), which may arise from large-scale refraction or from the truncation of scattering screens transverse to the Earth-pulsar line of sight.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/efbd8792c213d779ec26cb8918b11ab5ef9f3c9d

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

The pulsar spectral index distribution (2013, background): “Secondly, as signals from pulsars traverse the interstellar medium, they are scattered, which causes them to be broadened by a timescale which scales approximately as ν−3.5 for high-DM pulsars (Löhmer et al. 2001; Bhat et al. 2004).”
Spectral properties of 441 radio pulsars (2017, methodology): “We estimate the expected scatter broadening of the pulse profiles in the ISM as a fraction of pulse period using the empirical formula of Bhat et al. (2004): logτs =−6.46 + 0.154logDM+ 1.07(logDM)2−3.86logν , (19) where ν is the observing frequency in GHz and τs is the scattering time assuming thin…”
Pulsar searches and timing with the square kilometre array (2009, background): “Previous work (e.g. Lazio & Cordes 1998; Bhat et al. 2004; Cordes et al. 2004) shows that frequencies above 10 GHz are required to penetrate the scattering screen surrounding the Galactic centre.”
1E 1547.0–5408: A Radio-emitting Magnetar with a Rotation Period of 2 Seconds (2007, background): “1) is larger than for any known pulsar (see Bhat et al. 2004).”
THE GALACTIC POSITION DEPENDENCE OF FAST RADIO BURSTS AND THE DISCOVERY OF FRB011025 (2014, background): “We make the assumption that all bursts have an intrinsic duration ti much less than instrumental broadening and scattering effects, and use µ = −4.0 to appropriately scale Galactic scattering (Bhat et al. 2004).”
On the origin of a highly dispersed coherent radio burst (2012, background): “A steep power law, e.g. the Kolmogorov scenario with W ∝ f−4.4 can be ruled out, as can the predicted scatter broadening time of ∼ 130 ms from the empirical estimate of Bhat et al. (2004), although the latter is known to be uncertain to at least 2 orders of magnitude.”
Observing pulsars and fast transients with LOFAR (2011, background): “Considering the same pulsar and observing frequecy and system as discussed in the first paragraph of this section, and using the relation between dispersion measure and scattering from Bhat et al. (2004) we find that the scattering delay would lie between 0.01 and 1 s.”
Science with the Murchison Widefield Array (2012, background): “…duration do not survive passage through interplanetary, interstellar, or intergalactic plasma unscathed (Rickett 1990; Cordes et al. 1991; Taylor & Cordes 1993) and are distorted via dispersion (Cordes & Lazio 2002), scintillation (Rickett 1969), scattering (Bhat et al. 2004), and Faraday rotation.”