RXTE Monitoring of the Anomalous X-ray Pulsar 1E 1048.1-5937: Long-Term Variability and the 2007 March Event

TL;DR

This paper presents a comprehensive long-term study of the Anomalous X-ray Pulsar 1E 1048.1-5937, detailing its variability, glitches, flares, and bursts over a decade, and discusses these phenomena within the magnetar model framework.

Contribution

It provides the first detailed long-term timing, flux, and profile analysis of 1E 1048.1-5937, including the detection of multiple glitches, flares, and a burst, enhancing understanding of magnetar activity.

Findings

Detected a large glitch coinciding with a pulsed-flux flare in 2007.

Identified multiple glitches and flux variations over 10 years.

Discovered a small burst 27 days after the last flare.

Abstract

After three years of no unusual activity, Anomalous X-ray Pulsar 1E 1048.1-5937 reactivated in 2007 March. We report on the detection of a large glitch (Delta(nu)/nu =1.63(2)X~10^{-5}) on 2007 March 26 (MJD 54185.9), contemporaneous with the onset of a pulsed-flux flare, the third flare observed from this source in 10 years of monitoring with the Rossi X-ray Timing Explorer. Additionally, we report on a detailed study of the evolution of the timing properties, the pulsed flux, and the pulse profile of this source as measured by RXTE from 1996 July to 2008 January. In our timing study, we attempted phase coherent timing of all available observations. We show that in 2001, a timing anomaly of uncertain nature occurred near the rise of the first pulsed flux flare; we show that a likely glitch (Delta(nu)/nu =2.91(9)X10^{-6}) occurred in 2002, near the rise of the second flare, and we present a detailed description of the variations in the spin-down. In our pulsed flux study, we compare the decays of the three flares and discuss changes in the hardness ratio. In our pulse profile study, we show that the profile exhibited large variations near the peak of the first two flares, and several small short-term profile variations during the most recent flare. Finally, we report on the discovery of a small burst 27 days after the peak of the last flare, the fourth burst discovered from this source. We discuss the relationships between the observed properties in the framework of the magnetar model.