A weakening Compton hump and soft X-ray excess detected in the Seyfert-1 galaxy MCG-02-58-22
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2021-04-29
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Laha, Sibasish; Ghosh, Ritesh; A weakening Compton hump and soft X-ray excess detected in the Seyfert-1 galaxy MCG-02-58-22; The Astrophysical Journal, IOP Science (2021); https://arxiv.org/abs/2104.14627
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Abstract
We have carried out an extensive X-ray spectral study of the bare Seyfert-1 galaxy MCG--02--58--22 to ascertain the nature of the X-ray reprocessing media, using observations from Suzaku (2009) and simultaneous observations from XMM-Newton and NuSTAR (2016) . The most significant results of our investigation are: 1. The primary X-ray emission from the corona is constant in these observations, both in terms of the power law slope (Γ=1.80) and luminosity (L₂₋₁₀ₖₑᵥ=2.55×10⁴⁴ erg/s). 2. The soft excess flux decreased by a factor of two in 2016, the Compton hump weakened/vanished in 2016, and the narrow FeKα emission line became marginally broad (σ=0.35±0.08 keV) and its flux doubled in 2016. 3. From physical model fits we find that the normalization of the narrow component of the FeKα line does not change in the two epochs, although the Compton hump vanishes in the same time span. Since the primary X-ray continuum does not change, we presume that any changes in the reprocessed emission must arise due to changes in the reprocessing media. Our primary conclusions are: A. The vanishing of the Compton hump in 2016 can probably be explained by a dynamic clumpy torus which is infalling/outflowing, or by a polar torus wind. B. The torus in this AGN possibly has two structures: an equatorial toroidal disk (producing the narrow FeKα emission) and a polar component (producing the variable Compton hump), C. The reduction of the soft-excess flux by half and increase in the FeKα flux by a factor of two in the same period cannot be adequately explained by ionized disk reflection model alone.