X-ray observations of the new unusual magnetar Swift J1834.9-0846

We present X-ray observations of the new transient magnetar SwiftJ1834.9-0846, discovered with the Swift Burst Alert Telescope on 2011 August 7. The data were obtained with Swift, Rossi X-ray Timing Explorer (RXTE), CXO, and XMM-Newton both before and after the outburst. Timing analysis reveals single 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, s s^-1, and confirmed the high magnetic field of the source, B = 1.4 × 10¹⁴G. The decay of the persistent X-ray flux, spanning 48days, is consistent with a power law, Ft ^-0.5. In the CXO/Advanced CCD Imaging Spectrometer image, we find that the highly absorbed point source is surrounded by extended emission, which most likely is a dust scattering halo. SwiftJ1834.9-0846 is located near the center of the radio supernova remnant W41 and TeV source HESSJ1834-087. 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 SwiftJ1834.9-0846 revealed no source down to K_s ∼ 19.5 within the 06 CXO error circle.