2,665 research outputs found
Proving strong magnetic fields near to the central black hole in the quasar PG0043+039 via cyclotron lines
The optical luminous quasar PG0043+039 has not been detected before in deep
X-ray observations indicating the most extreme optical-to-X-ray slope index
of all quasars. This study aims to detect PG0043+039 in a deep
X-ray exposure. Furthermore, we wanted to check out whether this object shows
specific spectral properties in other frequency bands. We took deep X-ray
(XMM-Newton), far-ultraviolet (HST), and optical (HET, SALT telescopes) spectra
of PG0043+039 simultaneously in July 2013. We just detected PG0043+039 in our
deep X-ray exposure. The steep gradient is
consistent with an unusual steep gradient with
seen in the UV/far-UV continuum. The optical/UV
continuum flux has a clear maximum near 2500 {\AA}. The UV spectrum is very
peculiar because it shows broad humps in addition to known emission lines. A
modeling of these observed humps with cyclotron lines can explain their
wavelength positions, their relative distances, and their relative intensities.
We derive plasma temperatures of T 3keV and magnetic field strengths
of B 2 G for the line-emitting regions close to the
black hole.Comment: 4 pages, 3 figures, Astronomy & Astrophysics in pres
A long hard look at the minimum state of PG 2112+059 with XMM-Newton
XMM-Newton successfully detected the minimum state of PG 2112+059 during a
short snapshot observation and performed a long follow-up observation. The high
signal-to-noise spectra are modelled assuming different emission scenarios and
compared with archival spectra taken by XMM-Newton and Chandra.
The PG 2112+059 X-ray spectra acquired in May 2007 allowed the detection of a
weak iron fluorescent line, which is interpreted as being caused by reflection
from neutral material at some distance from the primary X-ray emitting source.
The X-ray spectra of PG 2112+059 taken at five different epochs during
different flux states can be interpreted within two different scenarios. The
first consists of two layers of ionised material with column densities of N_H
~5 x 10^22 cm^-2 and N_H ~3.5 x 10^23 cm^-2, respectively. The first layer is
moderately ionised and its ionisation levels follow the flux changes, while the
other layer is highly ionised and does not show any correlation with the flux
of the source. The spectra can also be interpreted assuming reflection by an
ionised accretion disk seen behind a warm absorber. The warm absorber
ionisation is consistent with being correlated with the flux of the source,
which provides an additional degree of self-consistency with the overall
reflection-based model. We explain the spectral variability with light bending
according to the models of Miniutti and Fabian and constrain the black hole
spin to be a/M > 0.86. Both scenarios also assume that a distant cold reflector
is responsible for the Fe K \alpha emission line.
Light bending provides an attractive explanation of the different states of
PG 2112+059 and may also describe the physical cause of the observed properties
of other X-ray weak quasars.Comment: 15 pages, 12 figures, A&A latex, accepted for publication in
Astronomy & Astrophysic
Genomic Evolution of Two Acinetobacter baumannii Clinical Strains from ST-2 Clones Isolated in 2000 and 2010 (ST-2_clon_2000 and ST-2_clon_2010)
Acinetobacter baumannii is a successful nosocomial pathogen due to its ability to persist in hospital environments by acquiring
mobile elements such as transposons, plasmids, and phages. In this study, we compared two genomes of A. baumannii clinical
strains isolated in 2000 (ST-2_clon_2000) and 2010 (ST-2_clon_2010) from GenBank project PRJNA308422
Infrared FeII Emission in Narrow-Line Seyfert 1 Galaxies
We obtained 0.8-2.4 micron spectra at a resolution of 320 km/s of four
narrow-line Seyfert 1 galaxies in order to study the near-infrared properties
of these objects. We focus on the analysis of the FeII emission in that region
and the kinematics of the low-ionization broad lines. We found that the 1
micron FeII lines (9997 A, 10501 A, 10863 A and 11126 A) are the strongest FeII
lines in the observed interval. For the first time, primary cascade lines of
FeII arising from the decay of upper levels pumped by Ly-alpha fluorescence are
resolved and identified in active galactic nuclei. Excitation mechanisms
leading to the emission of the 1 micron FeII features are discussed. A
combination of Ly-alpha fluorescence and collisional excitation are found to be
the main contributors. The flux ratio between near-IR FeII lines varies from
object to object, in contrast to what is observed in the optical region. A good
correlation between the 1 micron and optical FeII emission is found. This
suggests that the upper z4Fo and z4Do levels from which the bulk of the optical
lines descend are mainly populated by the transitions leading to the 1 micron
lines. The width and profile shape of FeII 11127, CaII 8642 and OI 8446 are
very similar but significantly narrower than Pa-beta, giving strong
observational support to the hypothesis that the region where FeII, CaII and OI
are produced are co-spatial, interrelated kinematically and most probably
located in the outermost portion of the BLR.Comment: Accepted for publication in ApJ - 35 page
The Reproducibility of Ultrasonographic Findings of Rectosigmoid Endometriosis Among Examiners With Different Level of Expertise
Objective: To analyze the reproducibility of ultrasonographic (US) findings of rectosigmoid endometriosis among examiners with different level of expertise using stored three-dimensional (3D) volumes of the posterior compartment of the pelvis as a part of SANABA (Sardinia-Navarra-Barcelona) collaborative study. Materials and methods: Six examiners in 3 academic Department of Obstetrics and Gynecology, with different levels of experience and blinded to each other, evaluated 60 stored 3D volumes from the posterior compartment of the pelvis and looked for the presence or absence of features of rectosigmoid endometriotic lesions defined as an irregular hypoechoic nodule with or without hypoechoic foci at the level of the muscularis propria of the anterior wall rectum sigma. Multiplanar view and virtual navigation were used. All examiners had to assess the 3D volume of posterior compartment of the pelvis and classify it as present or absent disease. To analyze intra-observer and the inter-observer agreements, each examiner performed the assessment twice with a 2-week interval between the first and second assessments. Reproducibility was assessed by calculating the weighted Kappa index. Results: Intra-observer reproducibility was moderate to very good for all observers (Kappa index ranging from 0.49 to 0.96) associated with a good diagnostic accuracy of each reader. Inter-observer reproducibility was fair to very good (Kappa index range: 0.21–0.87). Conclusions: The typical US sign of rectosigmoid endometriosis is reasonably recognizable to observers with different level of expertise when assessed in stored 3D volumes
An X-ray look at the Seyfert 1 Galaxy Mrk 590: XMM-Newton and Chandra reveal complexity in circumnuclear gas
This paper reports on a partially simultaneous observation of the bright Seyfert 1 Galaxy Mrk590, performed by XMM-Newton and Chandra. The long exposure (~100 ks) allows to investigate with great detail the Fe K complex at 6-7 keV and the presence of soft X-ray spectral features. We have analysed XMM-Newton data from the European Photon Imaging Camera (EPIC) in the 0.5-12 keV band and from the Reflection Grating Spectrometer (RGS) in the 0.35-2.5 keV band, and data from the High Energy Transmission Gratings (HETGs) onboard Chandra. UV and optical data from the Optical Monitor (OM) onboard XMM-Newton are also included in the analysis. The broad band spectrum is well described by an unabsorbed power law and three unresolved Fe~K lines in the 6-7 keV range. The presence of a Compton reflection component and a narrow Fe K line at 6.4 keV is consistent with an origin via torus reflection. The ionised Fe lines at ~6.7 and 7 keV are instead most likely originated by scattering on a warm and ionised gas. The soft X-ray spectrum appears to be almost featureless due to the very bright continuum emission, except for one emission line identified as OVIII Ly alpha detected at ~19 Angstrom by both RGS and Chandra-MEG. The emerging picture consists of an active nucleus seen directly on a "clean" line of sight without intervening material, surrounded by photoionised circumnuclear gas at a high ionisation level. We also study three serendipitous sources in the field of view of Chandra and XMM-Newton. One of these sources may be identified with an ULX of L_{0.3-10 keV}~10^{40} ergs/s
Dynamics of the Lyman alpha and C IV emitting gas in 3C 273
In this paper we study the variability properties of the Lyman alpha and C IV
emission lines in 3C273 using archival IUE observations. Our data show for the
first time the existence of variability on time scales of several years. We
study the spatial distribution and the velocity field of the emitting gas by
performing detailed analyses on the line variability using correlations, 1D and
2D response functions, and principal component analysis. In both lines we find
evidence for two components, one which has the dynamic properties of gas in
Keplerian motion around a black hole with a mass of the order of 10^9 Mo, and
one which is characterized by high, blue-shifted velocities at large lag. There
is no indication of the presence of optically thick emission medium neither in
the Lya, nor in the Civ response functions. The component characterized by
blue-shifted velocities, which is comparatively much stronger in Civ than in
Lya, is more or less compatible with being the result of gas falling towards
the central black hole with free-fall acceleration. We propose however that the
line emission at high, blue-shifted velocities is better explained in terms of
entrainment of gas clouds by the jet. This gas is therefore probably
collisionally excited as a result of heating due to the intense infrared
radiation from the jet, which would explain the strength of this component in
Civ relative to Lya. This phenomenon might be a signature of disk-jet
interaction.Comment: 16 pages, 10 figures. Accepted for publication in ApJ. Uses aaste
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