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On 1998 May 9–11, BeppoSAX observed the low-luminosity Seyfert 1 galaxy NGC 4051 in an ultra-dim X-ray state. The 2–10 keV flux (1.26 × 10−12 erg cm−2 s−1) was about 20 times fainter than its historical average value, and remained steady along the whole observation (∼2.3 d). The observed flat spectrum (Γ ≃ 0.8) and intense iron line (EW ≃ 600 eV) are best explained by assuming that the active nucleus has switched off, leaving only a residual reflection component visible.
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Guainazzi et al. (1998) studied this question.
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