Pulsar emission at the bottom end of the electromagnetic spectrum

TL;DR

This study uses LOFAR to analyze low-frequency pulsar emissions, revealing narrow spectral widths that support strong plasma turbulence models and providing new insights into pulsar radio emission mechanisms.

Contribution

It presents the first detailed LOFAR observations of pulsar single pulses at low frequencies, demonstrating intrinsic narrow spectral widths consistent with turbulence models.

Findings

Spectral width of bright pulses can be as narrow as 1 MHz.

Spectral width scales with frequency as df/f ~ 0.15.

Results support the strong plasma turbulence model.

Abstract

Pulsars are arguably the only astrophysical sources whose emission spans the entire electromagnetic spectrum, from decameter radio wavelengths to TeV energies. The LOw Frequency ARray (LOFAR) offers the unique possibility to study pulsars over a huge fractional bandwidth in the bottom 4 octaves of the radio window, from 15-240 MHz. Here we present a LOFAR study of pulsar single pulses, focussing specifically on the bright nearby pulsar B0809+74. We show that the spectral width of bright low-frequency pulses can be as narrow as 1 MHz and scales with increasing frequency as df/f ~ 0.15, at least in the case of the PSR B0809+74. This appears to be intrinsic to the pulsar, as opposed to being due to propagation effects. If so, this behavior is consistent with predictions by the strong plasma turbulence model of pulsar radio emission. We also present other observed properties of the single pulses and discuss their relation to other single-pulse phenomena like giant pulses.