BeppoSAX observations of Seyfert 1s in the Piccinotti sample I: poorly studied sources

In this work we present the first of two papers devoted to the study of the X-ray spectral characteristics of Seyfert 1 galaxies in the Piccinotti sample. In particular we analyse here the BeppoSAX broad band (0.1-100 keV) data of 4 objects which, despite their X-ray brightness, have been historically poorly studied due to their late identification with an AGN; these are H0111-149 (MKN1152), H0235-525 (ESO198-G24), H0557-385 (IRAS F05563-3820) and H1846-786 (IRAS F18389-7834). We have assumed for all the sources a baseline model which includes a power law with an exponential cut-off plus a reflection component and an iron K_alpha line; we have also searched for the presence of intrinsic absorption and/or a soft excess component. Our analysis indicates the presence of complex absorption in two objects (H0557-385 and H0111-149) best described by a combination of two uniform absorbers, one cold and one warm. Only in one source, H0557-385, a soft excess component has been measured. The primary continuum is best described by a canonical power law (Gamma=1.7-2) with a high energy cut-off in the range 40-130 keV. A cold reflection component is likely present in all sources with values ranging from less than 0.6 to higher than 2. In 3 out of 4 objects we find a cold iron line having equivalent width typical of Seyfert 1s (100-200 eV).Comment: 6 pages, 2 figures, accepted for publication as a Research Note in Astronomy and Astrophysic

Aggregative movement and front propagation for bi-stable population models

Front propagation for the aggregation-diffusion-reaction equation is investigated, where f is a bi-stable reaction-term and D(v) is a diffusion coefficient with changing sign, modeling aggregating-diffusing processes. We provide necessary and sufficient conditions for the existence of traveling wave solutions and classify them according to how or if they attain their equilibria at finite times. We also show that the dynamics can exhibit the phenomena of finite speed of propagation and/or finite speed of saturation

Diffusion-aggregation processes with mono-stable reaction terms

This paper analyses front propagation of the equation $u_\tau=[D(u)v_x]_x +f(v) \;\;\; \tau < 0, x \in \mathbb{R}$ where $f$ is a monostable (ie Fisher-type) nonlinear reaction term and $D(v)$ changes its sign once, from positive to negative values,in the interval $v \in[0,1]$ where the process is studied. This model equation accounts for simultaneous diffusive and aggregative behaviors of a population dynamic depending on the population density $v$ at time $\tau$ and position $x$. The existence of infinitely many travelling wave solutions is proven. These fronts are parametrized by their wave speed and monotonically connect the stationary states u = 0 and v = 1. In the degenerate case, i.e. when D(0) and/or D(1) = 0, sharp profiles appear, corresponding to the minimum wave speed. They also have new behaviors, in addition to those already observed in diffusive models, since they can be right compactly supported, left compactly supported, or both. The dynamics can exhibit, respectively, the phenomena of finite speed of propagation, finite speed of saturation, or both

Guiding-like functions for semilinear evolution equations with retarded nonlinearities

The paper deals with a semilinear evolution equation in a reflexive and separable Banach space. The non-linear term is multivalued, upper Caratheodory and it depends on a retarded argument. The existence of global almost exact, i.e. classical, solutions is investigated. The results are based on a continuation principle for condensing multifields and the required transversalities derive from the introduction of suitable generalized guiding functions. As a consequence, the equation has a bounded globally viable set.The results are new also in the lack of retard and in the single valued case. A brief discussion of a non-local diffusion model completes this investigation

X-ray view of four high-luminosity Swift/BAT AGN: Unveiling obscuration and reflection with Suzaku

The Swift/BAT nine-month survey observed 153 AGN, all with ultra-hard X-ray BAT fluxes in excess of 10^-11 erg cm^-2 s^-1 and an average redshift of 0.03. Among them, four of the most luminous BAT AGN (44.73 < Log L(BAT) < 45.31) were selected as targets of Suzaku follow-up observations: J2246.0+3941 (3C 452), J0407.4+0339 (3C 105), J0318.7+6828, and J0918.5+0425. The column density, scattered/reflected emission, the properties of the Fe K line, and a possible variability are fully analyzed. For the latter, the spectral properties from Chandra, XMM-Newton and Swift/XRT public observations were compared with the present Suzaku analysis. Of our sample, 3C 452 is the only certain Compton-thick AGN candidate because of i) the high absorption and strong Compton reflection; ii) the lack of variability; iii) the "buried" nature, i.e. the low scattering fraction (<0.5%) and the extremely low relative [OIII] luminosity. In contrast 3C 105 is not reflection-dominated, despite the comparable column density, X-ray luminosity and radio morphology, but shows a strong long-term variability in flux and scattering fraction, consistent with the soft emission being scattered from a distant region (e.g., the narrow emission line region). The sample presents high (>100) X-to-[OIII] luminosity ratios, confirming the [OIII] luminosity to be affected by residual extinction in presence of mild absorption, especially for "buried" AGN such as 3C 452. Three of our targets are powerful FRII radio galaxies, making them the most luminous and absorbed AGN of the BAT Seyfert survey despite the inversely proportional N_H - L_X relation.Comment: A&A paper in press, 17 page

The X-ray spectra of Compton-thick Seyfert 2 galaxies as seen by BeppoSAX

Results from BeppoSAX observations of Compton--thick Seyfert 2 galaxies are summarized and reviewed, and their general properties derived and discussed. In five out of the seven observed sources, the nucleus is directly visible at high X-ray energies, where the photons penetrate absorbers with column densities in the range 1.1-4.3x10^{24} cm-2 (in the other two sources, NGC 1068 and NGC 7674, the nucleus is instead totally obscured at all energies, implying even larger column densities). In most sources there is unambiguous evidence of a reflection component from optically thick, cold matter, while in two (or maybe four) cases there is also evidence of reflection from ionized matter. For the sources with a measured X-ray luminosity, a comparison with the infrared luminosity is made; while in two cases (the Circinus galaxy and NGC 4945) the IR emission appears to be dominated by starburst activity, in the other three sources (NGC 6240, Mrk 3 and TOL 0109-383) it is likely to be dominated by reprocessing of the UV and X-ray photons emitted by an AGN.Comment: Accepted for publication in MNRA