Wideband polarized radio emission from the newly revived magnetar XTE J1810-197

The anomalous X-ray pulsar XTE J1810-197 was the first magnetar found to emit pulsed radio emission. After spending almost a decade in a quiescent, radio-silent state, the magnetar was reported to have undergone a radio outburst in 2018 December. We observed radio pulsations from XTE J1810-197 during this early phase of its radio revival using the Ultra-Wideband Low receiver system of the Parkes radio telescope, obtaining wideband (704-4032 MHz) polarization pulse profiles, single pulses, and flux density measurements. Dramatic changes in polarization and rapid variations of the position angle of linear polarization across the main pulse and in time have been observed. The pulse profile exhibits similar structures throughout our three observations (over a week timescale), displaying a small amount of profile evolution in terms of polarization and pulse width across the wideband. We measured a flat radio spectrum across the band with a positive spectral index, in addition to small levels of flux and spectral index variability across our observing span. The observed wideband polarization properties are significantly different compared to those taken after the 2003 outburst, and therefore provide new information about the origin of radio emission.