ASCAObservations of the Ionized Gas in the Seyfert Galaxy NGC 3783

We present the results from ASCA observations of NGC 3783 carried out during1993 and 1996. Variability is observed both between the two epochs and withinthe individual observations, the latter due to a non-stationary process. We find the spectra at both epochs to contain features due to absorption byionized material, predominantly due to Ovii and Oviii. We find the opacity forsuch material to decrease by a factor approx 2 in the approx 0.7--1.0 keV bandbetween the epochs while the photoionizing flux increases by approx25%. Bycomparison with detailed photoionization models we show this behaviour isinconsistent with that expected from a single-zone of photoionized gas. Adeficit in the data compared to such models, consistent with excess absorptionby Oviii, supports the suggestion that the material consists of two or morezones. Significant Fe K-shell emission is also observed during both epochs. We showthis emission is dominated by the asymmetric line profile expected from theinnermost regions of the accretion flow. We find no evidence that the Feemission varied in either shape or equivalent width between the two epochs.