The spectacular X-ray echo of a magnetar burst

The Anomalous X-ray Pulsar (AXP) 1E 1547.0-5408 reactivated in 2009 January with the emission of dozens of short bursts. Follow-up observations with Swift/XRT and XMM-Newton showed the presence of multiple expanding rings around the position of the AXP. These rings are due to scattering, by different layers of interstellar dust, of a very high fluence burst emitted by 1E 1547.0-5408 on 2009 January 22. Thanks to the exceptional brightness of the X-ray rings, we could carry out a detailed study of their spatial and spectral time evolution until 2009 February 4. This analysis gives the possibility to estimate the distance of 1E 1547.0-5408. We also derived constraints on the properties of the dust and of the burst responsible for this rare phenomenon.

💡 Research Summary

The paper reports a remarkable X‑ray echo phenomenon associated with the anomalous X‑ray pulsar (AXP) 1E 1547.0‑5408, which entered an active phase in late January 2009. During this episode the source emitted dozens of short, intense bursts; one particularly powerful burst on 2009‑01‑22 produced a flash of X‑rays that was subsequently scattered by interstellar dust located at several distinct distances along the line of sight. The scattered photons arrived at Earth as expanding concentric rings, a classic “light‑echo” geometry first described for supernovae but rarely seen for magnetar bursts.

The authors used Swift/XRT and XMM‑Newton EPIC‑pn observations obtained from 2009‑01‑23 to 2009‑02‑04 to monitor the rings’ evolution. By fitting each image with a model consisting of a point‑source component (the direct afterglow) plus one or more thin annuli, they measured the rings’ radii, widths, surface brightness, and spectra at multiple epochs. The angular radius R of a ring follows the relation R = √