The Variable O Viii Warm Absorber in Mcg{6{30{15

We present the results of a 4 day ASCA observation of the Seyfert galaxy MCG{6{30{15, focusing on the nature of the X-ray absorption by the warm absorber, characterized by the K-edges of the highly ionized oxygen, Ovii and Oviii. We con rm that the column density of Oviii changes on a timescale of 10 4 s when the X-ray continuum ux decreases. The signi cant anti-correlation of column density with continuum ux gives direct evidence that the warm absorber is photoionized by the X-ray continuum. From the timescale of the variation of the Oviii column density, we estimate that it originates from gas within a radius of about 10 17 cm of the central engine. In contrast, the depth of the Ovii edge shows no response to the continuum ux, which indicates that it originates in gas at larger radii. Our results strongly suggest that there are two warm absorbing regions; one located near or within the Broad Line Region, the other associated with the outer molecular torus, scattering medium or Narrow Line Region.