433 research outputs found
The X-ray spectra of optically selected Seyfert 2 galaxies. Are there any Sy2 galaxies with no absorption?
We present an X-ray spectral analysis of a sample of 8 bona-fide Seyfert 2
galaxies, selected on the basis of their high flux, from
the Ho et al. (1997) spectroscopic sample of nearby galaxies. We find that, in
general, the X-ray spectra of our Seyfert 2 galaxies are complex, with some our
objects having spectra different from the 'typical' spectrum of X-ray selected
Seyfert 2 galaxies. Two (NGC3147 and NGC4698) show no evidence for intrinsic
absorption. We suggest this is due to the fact that when the torus suppresses
the intrinsic medium and hard energy flux, underlying emission from the host
galaxy, originating in circumnuclear starbursts, and scattering from warm
absorbers contributes in these energy bands more significantly. Our asca data
alone cannot discriminate whether low absorption objects are Compton-thick AGN
with a strong scattered component or lack an obscuring torus. The most striking
example of our low absorption Seyfert 2 is NGC4698. Its spectrum could be
explained by either a dusty warm absorber or a lack of broad line clouds so
that its appearance as a Seyfert 2 is intrinsic and not due to absorption.Comment: 12 pages, to be published in MNRA
XMM-Newton observations of ultraluminous X-ray sources in nearby galaxies
An XMM-Newton study of ultraluminous X-ray sources (ULX) has been performed
in a sample of 10 nearby Seyfert galaxies. Eighteen ULX have been found with
positional uncertainty of about 4". The large collecting area of XMM-Newton
makes the statistics sufficient to perform spectral fitting with simple models
in 8 cases. The main results of the present minisurvey strengthen the theory
that the ULX could be accreting black holes in hard or soft state. In some
cases, the contribution of the ULX to the overall X-ray flux appears to be
dominant with respect to that of the active nucleus. In addition, 6 ULX present
probable counterparts at other wavelengths (optical/infrared, radio). A
multiwavelength observing strategy is required to better assess the nature of
these sources.Comment: 10 pages, 11 figures. Accepted for publication by Astronomy and
Astrophysics. If you want figures at full resolution, please send an email to
Foschin
Increased percentage of L-selectin+ and ICAM-1+ peripheral blood CD4+/CD8+ T cells in active Graves' ophthalmopathy.
The purpose of the study was to evaluate the percentage of CD4+/CD8+ peripheral T cells expressing CD62L+ and CD54+ in patients with Graves' disease and to assess if these estimations could be helpful as markers of active ophthalmopathy. The study was carried out in 25 patients with Graves' disease (GD) divided into 3 groups: 1/ 8 patients with active Graves' ophthalmopathy (GO) (CAS 3-6, GO complaints pound 1 year), 2/ 9 patients with hyperthyroid GD without symptoms of ophthalmopathy (GDtox) and 3/ 8 patients with euthyroid GD with no GO symptoms (GDeu). The control group consisted of 15 healthy volunteers age and sex matched to groups 1-3. The expression of lymphocyte adhesion molecules was evaluated by using three-color flow cytometry. In GO group the percentage of CD8+CD54+, CD8+CD62L+, CD4+CD54+ and CD4+CD62L+ T cells was significantly higher as compared to controls (p<0.001, p<0.05, p<0.01, p<0.001 respectively). The percentage of CD8+CD54+ T lymphocytes was also elevated in GO group in comparison to hyperthyroid GD patients (p< 0.05). CD4+CD62L+ and CD8+CD54+ percentages were also increased in GDtox and GDeu as compared to controls. We found a positive correlation between the TSHRab concentration and the percentage of CD8+CD62L+ T cells in all studied groups (r= 0.39, p<0.05) and between the TSHRab level and CAS (r= 0.77, p<0.05). The increased percentage of CD8+CD54+ and CD8+CD62L+ T cells in patients with Graves' ophthalmopathy may be used as a marker of immune inflammation activity
Fosamprenavir or atazanavir once daily boosted with ritonavir 100 mg, plus tenofovir/emtricitabine, for the initial treatment of HIV infection: 48-week results of ALERT
<p>Abstract</p> <p>Background</p> <p>Once-daily (QD) ritonavir 100 mg-boosted fosamprenavir 1400 mg (FPV/r100) or atazanavir 300 mg (ATV/r100), plus tenofovir/emtricitabine (TDF/FTC) 300 mg/200 mg, have not been compared as initial antiretroviral treatment. To address this data gap, we conducted an open-label, multicenter 48-week study (ALERT) in 106 antiretroviral-naïve, HIV-infected patients (median HIV-1 RNA 4.9 log<sub>10 </sub>copies/mL; CD4+ count 191 cells/mm<sup>3</sup>) randomly assigned to the FPV/r100 or ATV/r100 regimens.</p> <p>Results</p> <p>At baseline, the FPV/r100 or ATV/r100 arms were well-matched for HIV-1 RNA (median, 4.9 log<sub>10 </sub>copies/mL [both]), CD4+ count (mean, 176 vs 205 cells/mm<sup>3</sup>). At week 48, intent-to-treat: missing/discontinuation = failure analysis showed similar responses to FPV/r100 and ATV/r100 (HIV-1 RNA < 50 copies/mL: 75% (40/53) vs 83% (44/53), p = 0.34 [Cochran-Mantel-Haenszel test]); mean CD4+ count change-from-baseline: +170 vs +183 cells/mm<sup>3</sup>, p = 0.398 [Wilcoxon rank sum test]). Fasting total/LDL/HDL-cholesterol changes-from-baseline were also similar, although week 48 median fasting triglycerides were higher with FPV/r100 (150 vs 131 mg/dL). FPV/r100-treated patients experienced fewer treatment-related grade 2–4 adverse events (15% vs 57%), with differences driven by ATV-related hyperbilirubinemia. Three patients discontinued TDF/FTC because their GFR decreased to <50 mL/min.</p> <p>Conclusion</p> <p>The all-QD regimens of FPV/r100 and ATV/r100, plus TDF/FTC, provided similar virologic, CD4+ response, and fasting total/LDL/HDL-cholesterol changes through 48 weeks. Fewer FPV/r100-treated patients experienced treatment-related grade 2–4 adverse events.</p
Exploring the spectral properties of faint hard X-ray sources with XMM-Newton
We present a spectroscopic study of 41 hard X-ray sources detected
serendipitously with high significance (> 5 sigma in the 2-10 keV band) in
seven EPIC performance/verification phase observations. The large collecting
area of EPIC allows us to explore the spectral properties of these faint hard
X-ray sources with 2< F_{2-10} < 80 x 10^{-14} erg cm^{-2}s^{-1} even though
the length of the exposures are modest (~ 20 ks). Optical identifications are
available for 21 sources of our sample. Using a simple power law plus Galactic
absorption model we find an average value of the photon index Gamma ~ 1.6-1.7,
broadly consistent with recent measurements made at similar fluxes with ASCA
and with Chandra stacked spectral analyses. We find that 31 out of 41 sources
are well fitted by this simple model and only eight sources require absorption
in excess of the Galactic value. Interestingly enough, one third of these
absorbed sources are broad line objects, though with moderate column densities.
Two sources in the sample are X-ray bright optically quiet galaxies and show
flat X-ray spectra. Comparing our observational results with those expected
from standard synthesis models of the cosmic X-ray background (CXB) we find a
fraction of unabsorbed to absorbed sources larger than predicted by theoretical
models at our completeness limit of F_{2-10} ~ 5 x 10^{-14} erg cm^{-2}s^{-1}.
The results presented here illustrate well how wide-angle surveys performed
with EPIC on board XMM-Newton allow population studies of interesting and
unusual sources to be made as well as enabling constraints to be placed on some
input parameters for synthesis models of the CXB.Comment: 16 pages, 11 figures. To be published in A&
NGC3147: a "true" Seyfert 2 without the broad-line region
We report on simultaneous optical and X-ray observations of the Seyfert
galaxy, NGC3147. The XMM-Newton spectrum shows that the source is unabsorbed in
the X-rays ( cm). On the other hand, no broad lines
are present in the optical spectrum. The origin of this optical/X-rays
misclassification (with respect to the Unification Model) cannot be attributed
to variability, since the observations in the two bands are simultaneous.
Moreover, a Compton-thick nature of the object can be rejected on the basis of
the low equivalent width of the iron K line ( eV) and the
large ratio between the 2-10 keV and the [OIII] fluxes. It seems therefore
inescapable to conclude that NGC3147 intrinsically lacks the Broad Line Region
(BLR), making it the first "true" Seyfert 2.Comment: 5 pages, 4 figures, accepted for publication in MNRAS Letter
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