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Register a new userHighly ionized disc and transient outflows in the Seyfert galaxy IRAS 18325-5926
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We report on strong X-ray variability and the Fe K band spectrum of the Seyfert galaxy IRAS 18325-5926 obtained from the 2001 XMM-Newton EPIC pn observation of a 120 ks duration. While the X-ray source is highly variable, the 8-10 keV band shows larger variability than that of the lower energies. Amplified 8-10 keV flux variations are associated with two prominent flares of the X-ray source during the observation. The Fe K emission is peaked at 6.6 keV with moderate broadening. It is likely to originate from a highly ionized disc with the ionization parameter of log xi ~3. The Fe K line flux responds to the major flare, supporting its disc origin. There is a short burst of the Fe line flux with no relation to the continuum brightness for which we have no clear explanation. We also find transient, blueshifted Fe K absorption features, which can be identified with high-velocity (~0.2 c) outflows of highly ionized gas, as found in other active galaxies. The deepest absorption feature appears only briefly (~1 hr) at the onset of the major flare and disappears when the flare is declining. The rapid evolution of the absorption spectrum makes this source peculiar among the active galaxies with high velocity outflows. Another detection of the absorption feature also precedes the other flare. The variability of the absorption feature partly accounts for the excess variability in the 8-10 keV band where the absorption feature appears. Although no reverberation measurement is available, the black hole mass of 2e6 Msun is inferred from the X-ray variability. When this mass is assumed, the black hole is accreting at around the Eddington limit, which may fit the highly ionized disc and strong outflows observed in this galaxy.
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We report our analysis of X-ray spectra of the Seyfert galaxy IRAS 18325-5926 (=Fairall 49) obtained from various X-ray observatories prior to XMM-Newton, including new results from two RXTE and one BeppoSAX observations. A relatively steep continuum slope (photon-index of ~2.2) in the 2-15 keV band is confirmed. The continuum spectrum observed with the BeppoSAX PDS shows a possible roll-over at energies above 30 keV, indicating a Comptonizing corona cooler than in other Seyfert nuclei. The X-ray spectrum above 2 keV is best explained with a model including reflection from a highly ionized disk with significant relativistic blurring. The iron K-alpha emission feature is then mainly due to FeXXV. The recent seven observations shows that the iron K emission flux appears to follow the continuum between the observations separated by a few months to years, although some exceptions suggest that the line strength may be determined in a more complex way.
For the past decade, ionized outflows of a few 100 km/s from nearby Seyfert galaxies have been studied in great detail using high resolution X-ray absorption spectra. A recurring feature of these outflows is their broad ionization distribution including essentially ions (e.g., of Fe) from neutral to fully ionized. The absorption measure distribution (AMD) is defined as the distribution of column density with ionization parameter |d N_H/d (log xi)|. AMDs of Seyfert outflows can span up to five orders of magnitude in xi. We present the AMD of five outflows and show that they are all rather flat, perhaps slightly rising towards high ionization. More quantitatively, a power-law fit for log AMD ~ (log xi)^a yields slopes of 0 < a < 0.4. These slopes tightly constrain the density profiles of the wind, which until now could be addressed only by theory. If the wind is distributed on large scales, the measured slopes imply a generic density radial profile of n ~ r^{-alpha} with 1 < alpha < 1.3. This scaling rules out a mass conserving radial flow of n ~ r^{-2}, or a constant density absorber, but is consistent with a non-spherical MHD outflow model in which n ~ r^{-1} along any given line of sight. On the other hand, if ionization variations are a result of local (delta r) density gradients, e.g. as in the turbulent interstellar medium (ISM), the AMD slopes imply density scaling of n ~ delta r^{-alpha} with 0.7 < alpha < 1.0, which is quite different from the scaling of approximately n ~ delta r^{0.4} found in the Milky Way ISM and typical of incompressible turbulence.
Ionized outflows, revealed by broad asymmetric wings of the [OIII] line, are commonly observed in AGN but the low intrinsic spatial resolution of observations has generally prevented a detailed characterization of their properties. The MAGNUM survey aims at overcoming these limitations by focusing on the nearest AGN, including NGC 1365, a nearby Seyfert galaxy (D~17 Mpc), hosting a low-luminosity AGN (Lbol ~ 2x10^43 erg/s). We want to obtain a detailed picture of the ionized gas in the central ~5 kpc of NGC 1365 in terms of physical properties, kinematics, and ionization mechanisms. We also aim to characterize the warm ionized outflow as a function of distance from the nucleus and its relation with the nuclear X-ray wind. We employed VLT/MUSE optical integral field spectroscopic observations to investigate the warm ionized gas and Chandra ACIS-S X-ray data for the hot highly-ionized phase. We obtained flux, kinematic, and diagnostic maps of the optical emission lines, which we used to disentangle outflows from disk motions and measure the gas properties down to a spatial resolution of ~70 pc. [OIII] emission mostly traces an AGN-ionized kpc-scale biconical outflow with velocities up to ~200 km/s. H{alpha} emission traces instead star formation in a circumnuclear ring and along the bar, where we detect non-circular motions. Soft X-rays are mostly due to thermal emission from the star-forming regions, but we could isolate the AGN photoionized component which matches the [OIII] emission. The mass outflow rate of the extended ionized outflow matches that of the nuclear X-ray wind and then decreases with radius. However, the hard X-ray emission from the circumnuclear ring suggests that star formation might contribute to the outflow. The integrated mass outflow rate, kinetic energy rate, and outflow velocity are broadly consistent with the typical relations observed in more luminous AGN.
We present the results of the analysis of the X-ray spectrum of the Seyfert 2 Mrk 348, observed by Suzaku and XMM-Newton. The overall spectrum of Mrk 348 can be described by a primary power law continuum seen through three layers of absorption, of which one is neutral and two are ionised. Comparing Suzaku (2008) and XMM-Newton (2002) observations we find variability of the X-ray spectral curvature. We suggest that the variability can be explained through the change of column density of both the neutral and one of the ionised absorbers, together with a variation of the ionisation level of the same absorber. We thus confirm one of the main features presented in past works, where intrinsic column density variability up to $sim 10^{23}$~cm$^{-2}$ was observed on time scales of months. We also find that the photon index of the underlying power law continuum ($Gamma sim 1.8$) is in agreement with the previous observations of this Seyfert 2.
In this paper we present a temporal and spectral analysis of X-ray data from the XMM and Chandra observations of the ultrasoft and variable Seyfert galaxy RX J1301.9+2747. In both observations the source clearly displays two distinct states in the X-ray band, a long quiescent state and a short flare (or eruptive) state which differs in count rates by a factor of 5--7. The transition from quiescent to flare state occurs in 1--2 ks. We have observed that the quiescent state spectrum is unprecedentedly steep with a photon index Gamma~7.1, and the spectrum of the flare state is flatter with Gamma~4.4. X-rays above 2 keV were not significantly detected in either state. In the quiescent state, the spectrum appears to be dominated by a black body component of temperature about ~30--40 eV, which is comparable to the expected maximum effective temperature from the inner accretion disk. The quiescent state however, requires an additional steep power-law, presumably arising from the Comptonization by transient heated electrons. Optical spectrum from the Sloan Digital Sky Survey shows Seyfert-like narrow lines for RX J1301.9+2747, while the HST imaging reveals a central point source for the object. In order to precisely determine the hard X-ray component, future longer X-ray observations are required. This will help constrain the accretion disk model for RX J1301.9+2747, and shed new light into the characteristics of the corona and accretion flows around black holes.
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