X-ray Observations of a New Unusual Magnetar Swift J1834.9-0846

TL;DR

This paper reports detailed X-ray observations of the newly discovered magnetar Swift J1834.9-0846, revealing its pulsation properties, magnetic field, flux decay, and potential environmental associations, contributing to magnetar phenomenology understanding.

Contribution

It provides the first comprehensive multi-instrument X-ray analysis of Swift J1834.9-0846, including timing, flux decay, and environmental context, highlighting its unusual high pulsed fraction and potential supernova remnant association.

Findings

Pulsation period of 2.4823 s with 85% pulsed fraction.

Estimated magnetic field of 1.4×10^{14} G.

Flux decay follows a t^{-0.5} power law over 48 days.

Abstract

We present X-ray observations of the new transient magnetar Swift J1834.9-0846, discovered with Swift BAT on 2011 August 7. The data were obtained with Swift, RXTE, CXO, and XMM-Newton both before and after the outburst. Timing analysis reveals singe peak pulsations with a period of 2.4823 s and an unusually high pulsed fraction, 85+/-10%. Using the RXTE and CXO data, we estimated the period derivative, dot{P}=8\times 10^{-12} s/s, and confirmed the high magnetic field of the source, B=1.4\times 10^{14} G. The decay of the persistent X-ray flux, spanning 48 days, is consistent with a power law, t^{-0.5}. In the CXO/ACIS image, we find that the highly absorbed point source is surrounded by extended emission, which most likely is a dust scattering halo. Swift J1834.9-0846 is located near the center of the radio supernova remnant W41 and TeV source HESS J1834-087. An association with W41 would imply a source distance of about 4 kpc; however, any relation to the HESS source remains unclear, given the presence of several other candidate counterparts for the latter source in the field. Our search for an IR counterpart of Swift J1834.9-0846 revealed no source down to K_s=19.5 within the 0.6' CXO error circle.