Discovery of the X-ray Counterpart to the Rotating Radio Transient J1819--1458

Abstract

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 {\sl 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 $N_H=7_{-4}^{+7}\times 10^{21}$ 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.

4 pages, 2 figures, submitted to ApJL