The Variable O VIII Warm Absorber in MCG–6–30–15

We present the results of a 4 day ASCA observation of the Seyfert galaxyMCG-6-30-15, focussing on the nature of the X-ray absorption by the warmabsorber, characterizd by the K-edges of the intermediately ionized oxygen,OVII and OVIII. We confirm that the column density of OVIII changes on atimescale of $\sim 10^4$~s when the X-ray continuum flux decreases. Thesignificant anti-correlation of column density with continuum flux gives directevidence that the warm absorber is photoionized by the X-ray continuum. Fromthe timescale of the variation of the OVIII column density, we estimate that itoriginates from gas within a radius of about $10^{17}\cm$ of the centralengine. In contrast, the depth of the OVII edge shows no response to thecontinuum flux, which indicates that it originates in gas at larger radii. Ourresults strongly suggest that there are two warm absorbing regions; one locatednear or within the Broad Line Region, the other associated with the outermolecular torus, scattering medium or Narrow Line Region.Comment: 8 pages (including figures) uuencoded gziped PS file. Submitted to Publications of the Astronomical Society of Japa