X-ray variability from the compact source in the supernova remnant RCW 103

A new ASCA observation of 1E 161348-5055, the central compact X-ray source in the supernova remnant RCW 103, reveals an order-of-magnitude decrease in its 3-10 keV flux since the previous ASCA measurement 4 yr earlier This re sult is difficult to reconcile with suggestions that the bulk of the emissi on is simple quasi-blackbody, cooling radiation from an isolated neutron st ar. Furthermore, archived Einstein and ROSAT data sets spanning 18 yr confi rm that this source manifests long-term variability, to a lesser degree. Th is provides a natural explanation for difficulties encountered in reproduci ng the original Einstein detection of IE 161348-5055. Spectra from the new data are consistent with no significant spectral change despite the decline in luminosity. We find no evidence for a pulsed component in any of the da ta sets, with a best upper limit on the pulsed modulation of 13%. We discus s the phenomenology of this remarkable source.