DISCOVERY OF EXTENDED X-RAY EMISSION AROUND THE HIGHLY MAGNETIC RRAT J1819-1458

We report on the discovery of extended X-ray emission around the high magnetic field rotating radio transient J1819-1458. Using a 30 ks Chandra ACIS-S observation, we found significant evidence for extended X-ray emission with a peculiar shape: a compact region out to similar to 5.'' 5, and more diffuse emission extending out to similar to 13 '' from the source. The most plausible interpretation is a nebula somehow powered by the pulsar, although the small number of counts prevents a conclusive answer on the nature of this emission. RRAT J1819-1458's spin-down energy loss rate ((E) over dot(rot) similar to 3 x 10(32) erg s(-1)) is much lower than that of other pulsars with observed spin-down-powered pulsar wind nebulae (PWNe), and implies a rather high X-ray efficiency of eta(X) equivalent to Lpwn; 0.5-8 keV/(E) over dot(rot) similar to 0.2 at converting spin-down power into the PWNX-ray emission. This suggests the need of an additional source of energy rather than the spin-down power alone, such as the high magnetic energy of this source. Furthermore, this Chandra observation allowed us to refine the positional accuracy of RRAT J1819-1458 to a radius of similar to 0.'' 3, and confirms the presence of X-ray pulsations and the similar to 1 keV absorption line, previously observed in the X-ray emission of this source.