Radio emission evolution, polarimetry and multifrequency single pulse analysis of the radio magnetar PSR J1622-4950

TL;DR

This study presents multi-frequency radio observations of the magnetar PSR J1622-4950, revealing variable flux, polarization, and pulse profiles, with insights into its magnetic geometry and emission mechanisms over 700 days.

Contribution

It provides the first comprehensive analysis of the polarization, pulse profile evolution, and single pulse properties of PSR J1622-4950 across multiple frequencies.

Findings

Flux density varies by a factor of 10 over days and decreases over 700 days.

Pulse profiles are highly polarized with complex polarization angle behavior.

Single pulses are narrow spikes whose widths inversely scale with frequency.

Abstract

Here we report on observations of the radio magnetar PSR J1622-4950 at frequencies from 1.4 to 17 GHz. We show that although its flux density is varying up to a factor of ~10 within a few days, it has on average decreased by a factor of 2 over the last 700 days. At the same time, timing analysis indicates a trend of decreasing spin-down rate over our entire data set, again of about a factor of 2 over 700 days, but also an erratic variability in the spin-down rate within this time span. Integrated pulse profiles are often close to 100 per cent linearly polarized, but large variations in both the profile shape and fractional polarization are regularly observed. Furthermore, the behaviour of the position angle of the linear polarization is very complex - offsets in both the absolute position angle and the phase of the position angle sweep are often seen and the occasional presence of orthogonal mode jumps further complicates the picture. However, model fitting indicates that the magnetic and rotation axes are close to aligned. Finally, a single pulse analysis has been carried out at four observing frequencies, demonstrating that the wide pulse profile is built up of narrow spikes of emission, with widths that scale inversely with observing frequency. All three of the known radio magnetars seem to have similar characteristics, with highly polarized emission, time-variable flux density and pulse profiles, and with spectral indices close to zero.