The X-ray Light Curve and CCD Spectra of SN 1978K

We provide an updated X-ray light curve and spectral fits of SN1978K using all available data from ROSAT,ASCA, Suzaku, Chandra, Swift, and XMM. The light curve and spectra cover 25 years of X-ray observationsof this object. Spectral fits were applied using two models: absorbed dual optically-thin thermal gas('vapec') and an absorbed thermal gas and non-equilibrium ionization model ('vapec' + 'vnei'). The softtemperatures cluster around 0.65-0.7 keV for both models. The hard temperatures lie typically in the 2-3 keVrange, but Several claims over the years have been made for enhanced abundances: Si, claimed to bedetected in a 2003 Chandra observation, is not confirmed. The abundance of He, claimed to be detected inXMM observations, requires more work as it is not consistently detected in all observations. The X-ray lightcurve shows considerable `bouncing', suggesting a variable circumstellar medium, but uncertainties are notnegligible.