Soft gamma repeaters activity in time

TL;DR

This paper explores the hypothesis that soft gamma repeater activity decreases over time similarly to pulsar glitches, suggesting younger sources are more active but produce less energetic flares.

Contribution

It proposes a model linking soft gamma repeater activity evolution to pulsar glitch laws, providing insights into their age-related activity and energy limits.

Findings

Younger soft gamma repeaters are more active.

Energy of giant flares is limited by magnetic field energy.

Activity decline follows a power-law similar to glitch evolution.

Abstract

In this short note I discuss the hypothesis that bursting activity of magnetars evolves in time analogously to the glitching activity of normal radio pulsars (i.e. sources are more active at smaller ages), and that the increase of the burst rate follows one of the laws established for glitching radio pulsars. If the activity of soft gamma repeaters decreases in time in the way similar to the evolution of core-quake glitches ($\propto t^{5/2}$), then it is more probable to find the youngest soft gamma repeaters, but the energy of giant flares from these sources should be smaller than observed $10^{44}$ --$10^{46}$ ergs as the total energy stored in a magnetar's magnetic field is not enough to support thousands of bursts similar to the prototype 5 March 1979 flare.