The extended X-ray emission around RRAT J1819-1458

We present new imaging and spectral analysis of the recently discovered extended X-ray emission around the high magnetic field rotating radio transient RRAT J1819-1458. We used two Chandra observations performed for this object in 2008 May 31 and 2011 May 28, respectively. The diffuse X-ray emissionwas detected with a significance of~19σ in the image obtained by combining the two observations. Neither long-term spectral nor timing variability has been observed from the source or the nebula. RRAT J1819-1458 shows an unusual high X-ray efficiency of ηX = LX(0.3-5 keV)/Ėrot~0.15 at converting spin-down power into X-ray luminosity. The most favourable scenario for the origin of this extended X-rayemission is either a pulsar wind nebula or a scattering halo. A magnetically powered scenario for the extended emission is viable only in the case of a Compton nebula, while it can be tentatively disfavoured in the case of synchrotron emission. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.