The second INTEGRAL AGN catalogue Beckmann, V.; Soldi, S.; Ricci, C. ...
Astronomy and astrophysics (Berlin),
10/2009, Letnik:
505, Številka:
1
Journal Article
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Aims. The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows testing of the unified scheme for AGN. Methods. We present analysis of ...INTEGRAL IBIS/ISGRI, JEM-X, and OMC data for 199 AGN supposedly detected by INTEGRAL above 20 keV. Results. The data analysed here allow significant spectral extraction on 148 objects and an optical variability study of 57 AGN. The slopes of the hard X-ray spectra of Seyfert 1 and Seyfert 2 galaxies are found to be consistent within the uncertainties, whereas higher cut-off energies and lower luminosities we measured for the more absorbed/type 2 AGN. The intermediate Seyfert 1.5 objects exhibit hard X-ray spectra consistent with those of Seyfert 1. When applying a Compton reflection model, the underlying continua appear the same in Seyfert 1 and 2 with Γ $\simeq$ 2, and the reflection strength is about R $\simeq$ 1, when assuming different inclination angles. A significant correlation is found between the hard X-ray and optical luminosity and the mass of the central black hole in the sense that the more luminous objects appear to be more massive. There is also a general trend toward the absorbed sources and type 2 AGN having lower Eddington ratios. The black hole mass appears to form a fundamental plane together with the optical and X-ray luminosity of the form $L_V \propto L_{\rm X}^{0.6} M_{\rm BH}^{0.2}$, similar to what is found between $L_{\it R}$, LX, and MBH. Conclusions. The transition from the type 1 to type 2 AGN appears to be smooth. The type 2 AGN are less luminous and have less accreting super massive black holes. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2, but seen under different inclination angles and absorption. The fundamental plane links the accretion mechanism with the bulge of the host galaxy and with the mass of the central engine in the same way in all types of Seyfert galaxies.
We present the first combined study of the recently discovered source IGR J16283-4838 with Swift, INTEGRAL, and RXTE. The source, discovered by INTEGRAL on 2005 April 7, shows a highly absorbed ...variable N sub(H) = (0.4-1.7) x 10 super(23) cm super(-2) and flat ( 6 1) spectrum in the Swift XRT and RXTE PCA data. No optical counterpart is detectable (V > 20 mag), but a possible infrared counterpart within the Swift XRT error radius is detected in the 2MASS and Spitzer GLIMPSE. The observations suggest that IGR J16283-4838 is a high-mass X-ray binary (HMXB) containing a neutron star embedded in Compton thick material. This makes IGR J16283-4838 a member of the class of highly absorbed HMXBs, discovered by INTEGRAL.
There is now abundant evidence that the luminosity of the Galactic super-massive black hole (SMBH) has not always been as low as it is nowadays. The observation of varying non-thermal diffuse X-ray ...emission in molecular complexes in the central 300 pc has been interpreted as delayed reflection of a past illumination by bright outbursts of the SMBH. The observation of different variability timescales of the reflected emission in the Sgr A molecular complex can be well explained if the X-ray emission of at least two distinct and relatively short events (i.e. about 10 yr or less) is currently propagating through the region. The number of such events or the presence of a long-duration illumination are open questions. Variability of the reflected emission all over of the central 300 pc, in particular in the 6.4 keV Fe Kα line, can bring strong constraints. To do so we performed a deep scan of the inner 300 pc with XMM-Newton in 2012. Together with all the archive data taken over the course of the mission, and in particular a similar albeit more shallow scan performed in 2000–2001, this allows for a detailed study of variability of the 6.4 keV line emission in the region, which we present here. We show that the overall 6.4 keV emission does not strongly vary on average, but variations are very pronounced on smaller scales. In particular, most regions showing bright reflection emission in 2000–2001 significantly decrease by 2012. We discuss those regions and present newly illuminated features. The absence of bright steady emission argues against the presence of an echo from an event of multi-centennial duration and most, if not all, of the emission can likely be explained by a limited number of relatively short (i.e. up to 10 yr) events.
Rifaximin, with its low systemic absorption, may represent a treatment of choice for irritable bowel syndrome (IBS), mainly due to its ability to act on IBS pathogenesis, through the influence on gut ...microbiota. The aim of the present study was to assess, by biomolecular tools, the rifaximin active modulation exerted on gut microbiota of non-constipated IBS patients. Fifteen non-constipated IBS subjects were treated with 550 mg rifaximin three times a day for 14 days. Stool samples were collected before starting the treatment, at the end of it, and after a 6-week washout period. Real-time polymerase chain reaction, denaturing gradient gel electrophoresis, and next-generation sequencing were applied to all the samples to verify and quantify possible microbial fluctuations. Rifaximin treatment did not affect the overall composition of the microbiota of the treated subjects, inducing fluctuations in few bacterial groups, balanced by the replacement of homologs or complementary bacterial groups. Rifaximin appeared to influence mainly potentially detrimental bacteria, such as Clostridium, but increasing the presence of some species, such as Faecalibacterium prausnitzii. A decrease in the Firmicutes/Bacteroidetes ratio after 14 days of treatment and bacterial profiles with higher biodiversity were observed during the follow-up compared to baseline. Rifaximin treatment, although effective on IBS symptom relief and normalization of lactulose breath test, did not induce dramatic shifts in the microbiota composition of the subjects, stimulating microbial reorganization in some populations toward a more diverse composition. It was not possible to speculate on differences of fecal microbiota modification between responders vs nonresponders and to correlate the quali-/quantitative modification of upper gastrointestinal microbiota and clinical response.
The thermal degradation of 2-hydroxy-3-ionene chloride polymer (HICP) and 3,22-ionene bromide (3,22) was studied in nitrogen atmosphere by thermogravimetry (TG) and infrared spectroscopy (FTIR). For ...the two polymers, a different profile in the TG/DTG curves was observed which was probably associated with the structural and functional differences between HICP and 3,22. The
E-values decreased from 150 to 105 kJ mol
−1 for the HICP and increased from 110 to 140 kJ mol
−1 for the 3,22 in the same range of weight loss fraction. The observed behaviour in terms of the TG/DTG curves and the activation energy values suggested that the 3,22 is more stable thermally than the HICP. This conclusion was supported by the FTIR spectra of the residues and evolved gas products of degradation. The mechanism of degradation was apparently associated with the scission of weak bonds and random scission of the polymer chain. Evolved gas products such as CO
2 and NH
3 in HICP and unsaturated hydrocarbons in 3,22 confirm the above mechanism.
The development of intestinal microflora in newborns is strictly related to the kind of feeding. Breast-fed infants, unlike the bottle-fed ones, have an intestinal ecosystem characterized by a strong ...prevalence of bifidobacteria and lactobacilli. Data available so far in the literature show that, among the numerous substances present in human milk, oligosaccharides have a clear prebiotic effect. They are quantitatively one of the main components of human milk and are only partially digested in the small intestine, so they reach the colon, where they stimulate selectively the development of bifidogenic flora. Such results have been recently proved both by characterization of oligosaccharides in breast-fed infant feces and by the study of intestinal microflora using new techniques of molecular analysis, confirming that human milk oligosaccharides represent the first prebiotics in humans.
Multiwavelength variability of blazars offers indirect insight into their powerful engines and on the mechanisms through which energy is propagated from the centre down the jet. The BL Lac object Mkn ...421 is a TeV emitter, a bright blazar at all wavelengths, and therefore an excellent target for variability studies. Mkn 421 was observed by INTEGRAL and Fermi-LAT in an active state on 16-21 April 2013. Well sampled optical, soft, and hard X-ray light curves show the presence of two flares. The average flux in the 20-100 keV range is 9.1e-11 erg/s/cm2 (~4.5 mCrab) and the nuclear average apparent magnitude, corrected for Galactic extinction, is V ~12.2. In the time-resolved X-ray spectra (3.5-60 keV), which are described by broken power laws and, marginally better, by log-parabolic laws, we see a hardening that correlates with flux increase, as expected in refreshed energy injections in a population of electrons that later cool via synchrotron radiation. The hardness ratios between the JEM-X fluxes in two different bands and between the JEM-X and IBIS/ISGRI fluxes confirm this trend. During the observation, the variability level increases monotonically from the optical to the hard X-rays, while the large LAT errors do not allow a significant assessment of the MeV-GeV variability. The cross-correlation analysis during the onset of the most prominent flare suggests a monotonically increasing delay of the lower frequency emission with respect to that at higher frequency, with a maximum time-lag of about 70 minutes, that is however not well constrained. The spectral energy distributions from the optical to the TeV domain are satisfactorily described by homogeneous models of blazar emission based on synchrotron radiation and synchrotron self-Compton scattering, except in the state corresponding to the LAT softest spectrum and highest flux.
The thermal degradation of N-(o-carboxybenzoyl)-l-phenylalanine (NCBPh), N-(o-carboxybenzoyl)-l-leucine (NCBL) and N-(o-carboxybenzoyl)-l-valine (NCBV) were studied by thermogravimetry and infrared ...spectroscopy. The results suggested that the loss of mass occurred by two main events which were defined as the imide formation and sublimation. The values of the activation energy (E) for the imide formation, considering both systems, were at the range 170–60kJ mol−1 and the results indicate that thermal stability obeys the order: NCBPh>NCBV>NCBL. The apparent activation energies obtained for the sublimation process are consistent with the structure of the imides N-Phthaloylphenylalanine (PhtPh), N-phthaloylvaline (PhtV) and N-phthaloylleucine (PhtL). The values of E are in the order PhtPh>PhtV>PhtL. This higher energy for the sublimation of the phenylalanine derivative, may be associated to the presence of the phenyl group, which favours the crystalline packing. In a sealed tube at higher temperature, we detected the degradation of the imide, with the concurrent appearance of CO2 (2370 and 2340cm−1), CO (2200–2100cm−1).
The relatively rapid spatial and temporal variability of the x-ray radiation from some molecular clouds near the Galactic center shows that this emission center component is due to the reflection of ...X-rays generated by a source that was luminous in the past, most likely the central supermassive black hole) Sagittarius A*. Studying the evolution of the molecular cloud reflection features is therefore a key element in reconstructing Sgr A*'s past activity. The aim of the present work is to study this emission on small angular scales in order to characterize the source outburst on short time scales. The variations likely stem from a highly variable active phase of Sgr A* which occured sometime within the past within few hundred years, and is characterized by at least two luminous outbursts with typical time scales of a few years and during which the Sgr A* luminosity went up to at least 10sup 39 ergssup -1.
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