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An Unveiling Event in the Type 2 AGN NGC4388: A Challenge for a Parsec Scale Absorber | | Martin Elvis
; G.Risaliti
; F. Nicastro
; J.M.Miller
; F .Fiore
; S.Puccetti
; | | Date: |
14 Jul 2004 | | Journal: | Astrophys.J. 615 (2004) L25-L28 | | Subject: | astro-ph | | Affiliation: | CfA), G.Risaliti (CFA & INAF, Arcetri), F. Nicastro (CfA), J.M.Miller (CfA), F .Fiore (INAF, Monteporzio) and S.Puccetti (INAF, Monteporzio | | Abstract: | We present two Rossi Xray Timing Explorer (RXTE) PCA observations of the type~2 Seyfert galaxy NGC 4388 caught in an unusual low X-ray absorption state. The observations were triggered by a detection in the 1.5-3 keV band of the RXTE All-Sky Monitor. NGC 4388 was found at a somewhat high continuum level (f(2-10 keV)=8x10(-11)erg cm(-2) s(-1)) and with a column density (N_H~3x10(22)cm(-2)), a factor ~10 lower than normal. The second PCA observation, four hours later, gave N_H<2x10(21)cm(-2) indicating, at the 3.1 sigma level, variability so rapid puts the absorber on a few 100 Schwartzschild radii scale, similar to the Broad Emission Line Region, or smaller. This small scale creates difficulties for the parsec-scale obscuring torus paradigm of Unified Schemes for type 1 and type 2 AGNs. | | Source: | arXiv, astro-ph/0407291 | | Services: | Forum | Review | PDF | Favorites | |
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