Swift observations of two outbursts from the magnetar 4U 0142+61

TL;DR

This study presents a detailed monitoring of the magnetar 4U 0142+61 over five years, documenting two significant radiative outbursts with associated timing anomalies, including a net spin-down glitch, and comparing these to similar events in other high-magnetic-field pulsars.

Contribution

It provides new observational data on two outbursts and associated timing events in 4U 0142+61, highlighting the occurrence of net spin-down glitches in high-B pulsars.

Findings

Two radiatively loud timing events observed with short gamma-ray bursts.

Long-lived flux decay associated with each outburst.

2015 event caused a net spin-down due to glitch over-recovery.

Abstract

4U 0142+61 is one of a small class of persistently bright magnetars. Here we report on a monitoring campaign of 4U 0142+61 from 2011 July 26 - 2016 June 12 using the Swift X-ray Telescope, continuing a 16 year timing campaign with the Rossi X-ray Timing Explorer. We show that 4U 0142+61 had two radiatively loud timing events, on 2011 July 29 and 2015 February 28, both with short soft gamma-ray bursts, and a long-lived flux decay associated with each case. We show that the 2015 timing event resulted in a net spin-down of the pulsar due to over-recovery of a glitch. We compare this timing event to previous such events in other high-magnetic-field pulsars, and discuss net spin-down glitches now seen in several young, high-B pulsars.