The lighthouse stays silent most of the time, but occasionally it emits a flare so bright it can be seen from hundreds of thousands of kilometers away. That's exactly how the magnetar XTE J1810-197 behaves — an ultra-dense star with a monstrous magnetic field. From September 2022 to July 2023, radio telescopes at the Argentine Institute of Radio Astronomy picked up its signals. During that time, they recorded 249 giant pulses — short but extremely powerful radio bursts.
These pulses don't occur just anywhere; they appear at a specific point in the star's rotation. If the magnetar is a spinning searchlight, the flares only show up when the beam points directly at us. The brightest pulses occupied only about two percent of the rotation period — a tiny 'window' during which the star manages to release energy comparable to that of small fast radio bursts coming from distant galaxies.
Why does this matter? Magnetars are among the most enigmatic objects in the universe. Their magnetic fields are billions of times stronger than those of ordinary neutron stars, and the mechanisms behind such flares remain poorly understood. Observations with new, upgraded radio telescopes show that even relatively modest instruments can catch these rare events and help unravel the nature of the most extreme 'radio stations' in the cosmos.
The brightest recorded pulse had a peak flux density of 119 janskys — roughly like trying to spot an ordinary light bulb from a distance of a few light-years.