Exceptional flaring activity of the anomalous X-ray pulsar 1E 1547.0-5408

TL;DR

This study reports on an extraordinary burst activity of the anomalous X-ray pulsar 1E 1547.0-5408 in 2009, revealing burst luminosities comparable to soft gamma repeaters and suggesting a unified nature of AXPs and SGRs.

Contribution

The paper presents the first detection of extremely luminous bursts from an AXP, comparable to SGR bursts, and analyzes their properties to support the unified model of these sources.

Findings

Burst luminosity > 1e42 erg/s, similar to SGRs.

Burst structure includes a short spike and extended tail with pulsations.

Supports the idea that AXPs and SGRs are the same source type.

Abstract

(Abridged) We studied an exceptional period of activity of the anomalous X-ray pulsar 1E 1547.0-5408 in January 2009, during which about 200 bursts were detected by INTEGRAL. The major activity episode happened when the source was outside the field of view of all the INTEGRAL instruments. But we were still able to study the properties of 84 bursts detected simultaneously by the anti-coincidence shield of the spectrometer SPI and by the detector of the imager ISGRI. We find that the luminosity of the 22 January 2009 bursts of 1E 1547.0-5408 was > 1e42 erg/s. This luminosity is comparable to that of the bursts of soft gamma repeaters (SGR) and is at least two orders of magnitude larger than the luminosity of the previously reported bursts from AXPs. Similarly to the SGR bursts, the brightest bursts of 1E 1547.0-5408 consist of a short spike of ~100 ms duration with a hard spectrum, followed by a softer extended tail of 1-10 s duration, which occasionally exhibits pulsations with the source spin period of ~2 s. The observation of AXP bursts with luminosities comparable to the one of SGR bursts strengthens the conjecture that AXPs and SGRs are different representatives of one and the same source type.