HEAD 2003 Meeting
Session 21. Active Galactic Nuclei III
Poster, Sunday-Wednesday, March 23, 2003, Duration of Meeting

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[21.18] Multi-Epoch XMM Observations of NGC4258

A. Fruscione, L. J. Greenhill, J. Moran (Center for Astrophysics), A. Filippenko (UC Berkeley), J. Herrnstein (Renaissance Technologies Corp.)

We observed the Seyfert 2 nucleus in NGC4258 four times between May 2001 and May 2002 for about 10ksec each with the instruments on board XMM. Our goal is to characterize variability in the X-ray spectrum - in particular the timescale for variability in the N(H) column density - and explore whether it is related to rotation of the molecular portion of the thin warped accretion disk in this system. NGC4258 is the galaxy for which the accretion disk structure is most well known, from direct mapping of water megamaser emission, and this makes it an important target for AGN studies.

We present here the analysis of the EPIC images and spectra, with additional emphasis on the energy band around the iron K\alpha line, which was (unexpectedly) not detected during a ~20ksec GTO observation in December 2000, despite previous detections using ASCA, SAX, and RXTE.

This work has been supported by the NASA contract NAS8-39073 to the Chandra X-Ray Center.

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Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.