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6th of April 2018
Extreme Scattering Events in pulsar light-curves
Kerr et al. have used the Parkes radiotelescope to measure the scintillation properties of 151 young, energetic pulsars and have reported the identification of two extreme scattering events (ESEs). One of these has a pronounced "double dip" in the measured flux density of PSR J1740−3015, similar to ESEs observed towards compact extragalactic radio sources. The figure above shows light curve, and dynamic spectra for PSR J1740−3015 over the eight year observing span. The top panel shows the band-averaged flux density (black circles) and the flux density for the top (blue upward-pointing triangles) and bottom (red downward-pointing triangles) halves of the band after scaling for the mean spectral index. The gray trace shows the flux variations predicted by a simple diverging lens model. The bottom panel shows the dynamic spectrum, averaged over time, for each observing epoch.

The observed shape is consistent with that produced by a diverging plasma lens with a size on the scale of many astronomical units (the Earth--Sun distance, 150 million km) with an electron density of ∼500 electons per cubic centimetre. These ESE detections indicate that well-calibrated pulsar monitoring is a keen tool for ESE detection and studies of the inter-stellar medium. More details are given in the full paper published in Monthly Notices of the Royal Astronomical Society.

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