The New Magnetar Swift J1822.3-1606

TL;DR

This paper reports the discovery and detailed timing and spectral analysis of the magnetar Swift J1822.3-1606, highlighting its low magnetic field and potential proximity, with implications for understanding magnetar properties.

Contribution

It provides the first detailed timing and flux evolution analysis of Swift J1822.3-1606, revealing its unusually low magnetic field among magnetars and suggesting it may be the nearest known example.

Findings

Spin-down rate of ~3x10^-13 s/s

Magnetic field of ~5x10^13 G, second lowest among magnetars

Possible distance of ~1.6 kpc, nearest magnetar if confirmed

Abstract

On 2011 July 14, a transient X-ray source, Swift J1822.3-1606, was detected by Swift BAT via its burst activities. It was subsequently identified as a new magnetar upon the detection of a pulse period of 8.4 s. Using follow-up RXTE, Swift, and Chandra observations, we have determined a spin-down rate of $\dot{P}\sim3\times10^{-13}$, implying a dipole magnetic field of $\sim5\times10^{13}$\,G, second lowest among known magnetars, although our timing solution is contaminated by timing noise. The post-outburst flux evolution is well modelled by surface cooling resulting from heat injection in the outer crust, although we cannot rule out other models. We measure an absorption column density similar to that of the open cluster M17 at 10\arcmin\ away, arguing for a comparable distance of $\sim$1.6\,kpc. If confirmed, this could be the nearest known magnetar.