  We consider the nature of the elusive neutron star candidate 1E~161348-5055
using X-ray observations obtained with the ASCA Observatory. The compact X-ray
source is centered on the shell-type Galactic supernova remnant RCW103 and has
been interpreted as a cooling neutron star associated with the remnant. The
X-ray spectrum of the remnant shell can be characterized by a non-equilibrium
ionization (NEI) thermal model for a shocked plasma of temperature kT ~ 0.3
keV. The spectrum falls off rapidly above 3 keV to reveal a point source in the
spectrally-resolved images, at the location of 1E~161348-5055. A black-body
model fit to the source spectrum yields a temperature kT = 0.6 keV, with an
unabsorbed 0.5-10 keV luminosity of Lx ~ 10E34 erg/s (for an assumed distance
of 3.3 kpc, both of which are at least a factor of 2 higher than predicted by
cooling neutron star models. Alternatively, a power-law model for the source
continuum gives a steep photon index of ~ 3.2, similar to that of other
radio-quiet, hard X-ray point sources associated with supernova remnants.
1E~161348-5055 may be prototypical of a growing class of radio-quiet neutron
stars revealed by ASCA; we suggest that these objects account for previously
hidden neutron stars associated with supernova remnants.
