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Revealing the Dusty Warm Absorber in MCG--6-30-15 with the Chandra HETG | | J.C. Lee
; P.M. Ogle
; C.R. Canizares
; H.L. Marshall
; N.S.Schulz
; R. Morales
; A.C. Fabian
; K. Iwasawa
; | | Date: |
4 Dec 2000 | | Journal: | ApJ., 554, L13 (2001) | | Subject: | astro-ph | | Affiliation: | MIT), R. Morales, A.C. Fabian, K. Iwasawa (IoA-Cambridge | | Abstract: | We present detailed evidence for a warm absorber in the Seyfert 1 galaxy MCG--6-30-15 and dispute earlier claims for relativistic O line emission. The HETG spectra show numerous narrow, unresolved (FWHM < 200 km/s) absorption lines from a wide range of ionization states of N, O, Mg, Ne, Si, S, Ar, and Fe. The O VII edge and 1s^2--1snp resonance line series to n=9 are clearly detected at rest in the AGN frame. We attribute previous reports of an apparently highly redshifted O VII edge to the 1s^2--1snp (n > 5) O VII resonance lines, and a neutral Fe L absorption complex. The shape of the Fe L feature is nearly identical to that seen in the spectra of several X-ray binaries, and in laboratory data. The implied dust column density agrees with that obtained from reddening studies, and gives the first direct X-ray evidence for dust embedded in a warm absorber. The O VIII resonance lines and weak edge are also detected, and the spectral rollover below 2 keV is explained by the superposition of numerous absorption lines and edges. We identify, for the first time, a KLL resonance in the O VI photoabsorption cross section, giving a measure of the O VI column density. The O VII (f) emission detected at the systemic velocity implies a covering fraction of ~5% (depending on the observed vs. time-averaged ionizing flux). Our observations show that a dusty warm absorber model is not only adequate to explain all the spectral features > 0.48 keV (< 26 AA) the data REQUIRE it. This contradicts the interpretation of Branduardi-Raymont et al. (2001) that this spectral region is dominated by highly relativistic line emission from the vicinity of the black hole. | | Source: | arXiv, astro-ph/0101065 | | Services: | Forum | Review | PDF | Favorites | |
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