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Register a new userThe X-ray emission of the Seyfert 2 galaxy MCG-01-24-12
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We present a detailed X-ray spectral analysis of the nearby Seyfert 2 galaxy MCG-01-24-12 based on a multi-epoch data set. Data have been taken with different X-ray satellites, namely XMM-Newton, NuSTAR, Swift and Chandra and cover different time intervals, from years down to a few days. From 2006 to 2013 the source had a 2-10 keV flux of $sim$1.5$times$10$^{-11}$ erg cm$^{-2}$ s$^{-1}$, consistent with archival observations based on textit{HEAO} and textit{BeppoSAX} data, though a 2019 textit{Chandra} snapshot caught the source in an extreme low flux state, a factor of $sim$10 fainter than its historical one. Based on phenomenological and physically motivated models, we find the X-ray spectrum of MCG-01-24-12 to be best modelled by a power-law continuum emission with $Gamma$=1.76$pm$0.09 with a high energy cut-off at E$_{rm c}=70^{+21}_{-14}$ keV that is absorbed by a fairly constant column density of N$_{rm H}$=(6.3$pm$0.5)$times10^{22}$ cm$^{-2}$. These quantities allowed us to estimate the properties of the hot corona in MCG-01-24-12 for the cases of a spherical or slab-like hot Comptonising plasma to be kT$_{rm e}$=27$^{+8}_{-4}$ keV, $tau_{rm e}$=5.5$pm$1.3 and kT$_{rm e}$=28$^{+7}_{-5}$ keV, $tau$=3.2$pm$0.8, respectively. Finally, despite the short duration of the exposures, possible evidence of the presence of outflows is discussed.
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We have carried out an extensive X-ray spectral study of the bare Seyfert-1 galaxy MCG--02--58--22 to ascertain the nature of the X-ray reprocessing media, using observations from Suzaku (2009) and simultaneous observations from XMM-Newton and NuSTAR (2016) . The most significant results of our investigation are: 1. The primary X-ray emission from the corona is constant in these observations, both in terms of the power law slope ($Gamma=1.80$) and luminosity ($L_{2-10 rm keV}= 2.55times 10^{44} $ 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 FeK$alpha$ emission line became marginally broad ($sigma=0.35pm0.08$ keV) and its flux doubled in 2016. 3. From physical model fits we find that the normalization of the narrow component of the FeK$alpha$ 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 FeK$alpha$ emission) and a polar component (producing the variable Compton hump), C. The reduction of the soft-excess flux by half and increase in the FeK$alpha$ flux by a factor of two in the same period cannot be adequately explained by ionized disk reflection model alone.
We report the results of a detailed analysis of a deep simultaneous $130,rm ks$ textit{XMM-Newton & NuSTAR} observation of the nearby ($z=0.0315$) and bright ($L_{rm bol}sim3times10^{45},rm erg,s^{-1}$) starburst-AGN Seyfert,2 system: MCG--03--58--007. From the broadband fitting we show that most of the obscuration needs to be modeled with a toroidal type reprocessor such as texttt{MYTorus} citep{MurphyYaqoob09}. Nonetheless the signature of a powerful disc-wind is still apparent at higher energies and the observed rapid short-term X-ray spectral variability is more likely caused by a variable zone of highly ionized fast wind rather than by a neutral clumpy medium. We also detect X-ray emission from larger scale gas as seen from the presence of several soft narrow emission lines in the RGS, originating from a contribution of a weak star forming activity together with a dominant photoionized component from the AGN.
Mkn 3 is a Seyfert 2 galaxy that is widely regarded as an exemplary Compton-thick AGN. We study the Suzaku X-ray spectrum using models of the X-ray reprocessor that self-consistently account for the Fe K$alpha$ fluorescent emission line and the associated Compton-scattered, or reflection, continuum. We find a solution in which the average global column density, $0.234^{+0.012}_{-0.010} times 10^{24} rm cm^{-2}$, is very different to the line-of-sight column density, $0.902^{+0.012}_{-0.013} times 10^{24} rm cm^{-2}$. The global column density is $sim 5$ times smaller than that required for the matter distribution to be Compton-thick. Our model accounts for the profiles of the Fe K$alpha$ and Fe K$beta$ lines, and the Fe K edge remarkably well, with a solar abundance of Fe. The matter distribution could consist of a clumpy medium with a line-of-sight column density higher than the global average. A uniform, spherically-symmetric distribution alone cannot simultaneously produce the correct fluorescent line spectrum and reflection continuum. Previous works on Mkn 3, and other AGN, that assumed a reflection continuum from matter with an infinite column density could therefore lead to erroneous or puzzling conclusions if the matter out of the line-of-sight is really Compton-thin. Whereas studies of samples of AGN have generally only probed the line-of-sight column density, with simplistic, one-dimensional models, it is important now to establish the global column densities in AGN. It is the global properties that affect the energy budget in terms of reprocessing of X-rays into infrared emission, and that constrain population synthesis models of the cosmic X-ray background.
We present the result of the Chandra high-resolution observation of the Seyfert~2 galaxy NGC 7590. This object was reported to show no X-ray absorption in the low-spatial resolution ASCA data. The XMM observations show that the X-ray emission of NGC 7590 is dominated by an off-nuclear ultra-luminous X-ray source (ULX) and an extended emission from the host galaxy, and the nucleus is rather weak, likely hosting a Compton-thick AGN. Our recent Chandra observation of NGC 7590 enables to remove the X-ray contamination from the ULX and the extended component effectively. The nuclear source remains undetected at ~4x10^{-15} erg/s/cm^-2 flux level. Although not detected, Chandra data gives a 2--10 keV flux upper limit of ~6.1x10^{-15} erg/s/cm^-2 (at 3 sigma level), a factor of 3 less than the XMM value, strongly supporting the Compton-thick nature of the nucleus. In addition, we detected five off-nuclear X-ray point sources within the galaxy D25 ellipse, all with 2 -- 10 keV luminosity above 2x10^{38} erg/s (assuming the distance of NGC 7590). Particularly, the ULX previously identified by ROSAT data was resolved by Chandra into two distinct X-ray sources. Our analysis highlights the importance of high spatial resolution images in discovering and studying ULXs.
We present a flux-resolved X-ray analysis of the dwarf Seyfert 1.8 galaxy NGC 4395, based on three archival $XMM-Newton$ and one archival $NuSTAR$ observations. The source is known to harbor a low mass black hole ($sim 10^4- {rm a~ few~}times 10^{5}~rm M_odot$) and shows strong variability in the full X-ray range during these observations. We model the flux-resolved spectra of the source assuming three absorbing layers: neutral, mildly ionized, and highly ionized ($N_{rm H} sim 1.6times 10^{22}-3.4 times 10^{23}~rm cm^{-2}$, $sim 0.8-7.8 times 10^{22}~rm cm^{-2}$, and $ 3.8 times 10^{22}~rm cm^{-2}$, respectively. The source also shows intrinsic variability by a factor of $sim 3$, on short timescales, due to changes in the nuclear flux, assumed to be a power law ($Gamma = 1.6-1.67$). Our results show a positive correlation between the intrinsic flux and the absorbers ionization parameter. The covering fraction of the neutral absorber varies during the first $XMM-Newton$ observation, which could explain the pronounced soft X-ray variability. However, the source remains fully covered by this layer during the other two observations, largely suppressing the soft X-ray variability. This suggests an inhomogeneous and layered structure in the broad line region. We also find a difference in the characteristic timescale of the power spectra between different energy ranges and observations. We finally show simulated spectra with $XRISM$, $Athena$, and $eXTP$, which will allow us to characterize the different absorbers, study their dynamics, and will help us identify their locations and sizes.
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