Discovery of the X-ray counterpart to the Rotating RAdio Transient J1819-1458

We present the discovery of the first X-ray counterpart to a Rotating RAdio Transient (RRAT) source. RRAT J1819-1458 is a relatively highly magnetized (G) member of a new class of unusual pulsar-like objects discovered by their bursting activity at radio wavelengths. A Chandra observation of that position revealed a pointlike source, CXOU J181934.1-145804, with a soft spectrum well fit by an absorbed blackbody with N-H = 7(-4)(+7) X 10(21)cm(-2), temperature kT = 0.12 +/- 0.04 keV, and an unabsorbed flux of similar to 2 X 10(-12) ergs cm(-2) s(-1) between 0.5 and 8 keV. No optical or infrared (IR) counterparts are visible within 1" of our X- ray position. The positional coincidence, spectral properties, and lack of an optical/IR counterpart make it highly likely that CXOU J181934.1 - 145804 is a neutron star and is the same object as RRAT J1819 - 1458. The source showed no variability on any timescale from the pulse period of 4.26 s up to the 5 day window covered by the observations, although our limits (especially for pulsations) are not particularly constraining. The X-ray properties of CXOU J181934.1 145804, while not yet measured to high precision, are similar to those of comparably aged radio pulsars and are consistent with thermal emission from a cooling neutron star.