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 ( B \sim 5 \times 10 ^ { 13 } G ) member of a new class of unusual pulsar-like objects discovered by their bursting activity at radio wavelengths .
The position of RRAT J1819–1458 was serendipitously observed by the Chandra ACIS-I camera in 2005 May .
At that position we have discovered a pointlike source , CXOU J181934.1–145804 , with a soft spectrum well fit by an absorbed blackbody with N _ { H } = 7 ^ { +7 } _ { -4 } \times 10 ^ { 21 } cm ^ { -2 } and temperature kT = 0.12 \pm 0.04 keV , having an unabsorbed flux of \sim 2 \times 10 ^ { -12 } ergs cm ^ { -2 } s ^ { -1 } between 0.5 and 8 keV .
No optical or infrared ( IR ) counterparts are visible within 1 ^ { \prime \prime } 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 five-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 .