NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-25 T13:55:54 PDT
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For refcode 2009ApJ...705..496M:
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Copyright by American Astronomical Society. Reproduced by permission
2009ApJ...705..496M A Suzaku Observation of NGC 4593: Illuminating the Truncated Disk Markowitz, A. G.; Reeves, J. N. Abstract. We report results from a 2007 Suzaku observation of the Seyfert 1 AGN NGC 4593. The narrow Fe K{alpha} emission line has a FWHM width ~ 4000 km s^-1^, indicating emission from >~ 5000 R_g_. There is no evidence for a relativistically broadened Fe K line, consistent with the presence of a radiatively efficient outer disk which is truncated or transitions to an interior radiatively inefficient flow. The Suzaku observation caught the source in a low-flux state; comparison to a 2002 XMM-Newton observation indicates that the hard X-ray flux decreased by 3.6, while the Fe K{alpha} line intensity and width {sigma} each roughly halved. Two model-dependent explanations for the changes in Fe K{alpha} line profile are explored. In one, the Fe K{alpha} line width has decreased from ~10,000 to ~4000 km s^-1^ from 2002 to 2007, suggesting that the thin disk truncation/transition radius has increased from 1000-2000 to >~5000 R_g_. However, there are indications from other compact accreting systems that such truncation radii tend to be associated only with accretion rates relative to Eddington much lower than that of NGC 4593. In the second model, the line profile in the XMM-Newton observation consists of a time-invariant narrow component plus a broad component originating from the inner part of the truncated disk (~300 R_g_) which has responded to the drop in continuum flux. The Compton reflection component strength R is ~ 1.1, consistent with the measured Fe K{alpha} line total equivalent width with an Fe abundance 1.7 times the solar value. The modest soft excess, modeled well by either thermal bremsstrahlung emission or by Comptonization of soft seed photons in an optical thin plasma, has fallen by a factor of ~20 from 2002 to 2007, ruling out emission from a region 5 lt-yr in size. Key words: galaxies: active, galaxies: individual: NGC 4593, galaxies: Seyfert, X-rays: galaxies
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