681 research outputs found
XMM-Newton observation of the interacting galaxies NGC1512 and NGC1510
The galaxy NGC1512 is interacting with the smaller galaxy NGC1510 and shows a
peculiar morphology, characterised by two extended arms immersed in an HI disc
whose size is about four times larger than the optical diameter of NGC1512. For
the first time we performed a deep X-ray observation of the galaxies NGC1512
and NGC1510 with XMM-Newton to gain information on the population of X-ray
sources and diffuse emission in a system of interacting galaxies. We identified
and classified the sources detected in the XMM-Newton field of view by means of
spectral analysis, hardness-ratios calculated with a Bayesian method, X-ray
variability, and cross-correlations with catalogues in optical, infrared, and
radio wavelengths. We also made use of archival Swift (X-ray) and Australia
Telescope Compact Array (radio) data to better constrain the nature of the
sources detected with XMM-Newton. We detected 106 sources in the energy range
of 0.2-12 keV, out of which 15 are located within the D_25 regions of NGC1512
and NGC1510 and at least six sources coincide with the extended arms. We
identified and classified six background objects and six foreground stars. We
discussed the nature of a source within the D_25 ellipse of NGC1512, whose
properties indicate a quasi-stellar object or an intermediate ultra-luminous
X-ray source. Taking into account the contribution of low-mass X-ray binaries
and active galactic nuclei, the number of high-mass X-ray binaries detected
within the D_25 region of NGC1512 is consistent with the star formation rate
obtained in previous works based on radio, infrared optical, and UV
wavelengths. We detected diffuse X-ray emission from the interior region of
NGC1512 with a plasma temperature of kT=0.68(0.31-0.87) keV and a 0.3-10 keV
X-ray luminosity of 1.3E38 erg/s, after correcting for unresolved discrete
sources.Comment: Accepted for publication in Astronomy and Astrophysics. 20 pages.
Appendix B will be published electronically onl
Spatial distribution of unidentified infrared bands and extended red emission in the compact galactic HII region Sh 152
We present visible and near IR images of the compact HII region Sh 152. Some
of these images reveal the presence of Extended Red Emission (ERE) around 698
nm and emission from Unidentified Infra Red Bands (UIRBs) at 3.3 and 6.2
micron. Other images show the near infrared (7-12 micron) continuous emission
of the nebula. The ERE emission is found to coincide with the ionized region
and significantly differ from the UIRBs location. Also some evidence is found
in favor of grains as carriers for ERE.Comment: 3 pages, 4 figures, to be published in the proceedings of the
colloquium "The universe as seen by ISO" help in Paris, October 20-23, 1998 ;
available in html format at http://www.obs-hp.fr/preprints.htm
Le genre Abies en Italie: écologie générale, gestion sylvicole et ressources génétiques.
International audienceLe genre Abies est représenté en Italie par deux espèces indigènes : A. alba et A. nebrodensis. A. alba (63.400 ha) est localisé dans les Alpes et dans les Apennins, jusqu'à l'Aspromonte, en Calabre. L'article fournit d'abord un aperçu historique, puis écologique de l'utilisation des sapinières. Il décrit ensuite la gestion naturelle des ressources génétiques. Importante bibliographie
High frequency GaAs nano-optomechanical disk resonator
Optomechanical coupling between a mechanical oscillator and light trapped in
a cavity increases when the coupling takes place in a reduced volume. Here we
demonstrate a GaAs semiconductor optomechanical disk system where both optical
and mechanical energy can be confined in a sub-micron scale interaction volume.
We observe giant optomechanical coupling rate up to 100 GHz/nm involving
picogram mass mechanical modes with frequency between 100 MHz and 1 GHz. The
mechanical modes are singled-out measuring their dispersion as a function of
disk geometry. Their Brownian motion is optically resolved with a sensitivity
of 10^(-17)m/sqrt(Hz) at room temperature and pressure, approaching the quantum
limit imprecision.Comment: 7 pages, 3 figure
Swift/XRT orbital monitoring of the candidate supergiant fast X-ray transient IGR J17354-3255
We report on the Swift/X-ray Telescope (XRT) monitoring of the field of view
around the candidate supergiant fast X-ray transient (SFXT) IGR J17354-3255,
which is positionally associated with the AGILE/GRID gamma-ray transient AGL
J1734-3310. Our observations, which cover 11 days for a total on-source
exposure of about 24 ks, span 1.2 orbital periods (P_orb=8.4474 d) and are the
first sensitive monitoring of this source in the soft X-rays. These new data
allow us to exploit the timing variability properties of the sources in the
field to unambiguously identify the soft X-ray counterpart of IGR J17354-3255.
The soft X-ray light curve shows a moderate orbital modulation and a dip. We
investigated the nature of the dip by comparing the X-ray light curve with the
prediction of the Bondi-Hoyle-Lyttleton accretion theory, assuming both
spherical and nonspherical symmetry of the outflow from the donor star. We
found that the dip cannot be explained with the X-ray orbital modulation. We
propose that an eclipse or the onset of a gated mechanism is the most likely
explanation for the observed light curve.Comment: Accepted for publication in Astronomy and Astrophysics. 9 page
On-chip III-V monolithic integration of heralded single photon sources and beamsplitters
We demonstrate a monolithic III-V photonic circuit combining a heralded
single photon source with a beamsplitter, at room temperature and telecom
wavelength. Pulsed parametric down-conversion in an AlGaAs waveguide generates
counterpropagating photons, one of which is used to herald the injection of its
twin into the beamsplitter. We use this configuration to implement an
integrated Hanbury-Brown and Twiss experiment, yielding a heralded second-order
correlation that confirms single-photon
operation. The demonstrated generation and manipulation of quantum states on a
single III-V semiconductor chip opens promising avenues towards real-world
applications in quantum information
Giant outburst from the supergiant fast X-ray transient IGR J17544-2619: accretion from a transient disc?
Supergiant fast X-ray transients (SFXTs) are high mass X-ray binaries
associated with OB supergiant companions and characterised by an X-ray flaring
behaviour whose dynamical range reaches 5 orders of magnitude on timescales of
a few hundred to thousands of seconds. Current investigations concentrate on
finding possible mechanisms to inhibit accretion in SFXTs and explain their
unusually low average X-ray luminosity. We present the Swift observations of an
exceptionally bright outburst displayed by the SFXT IGR J17544-2619 on 2014
October 10 when the source achieved a peak luminosity of erg
s. This extends the total source dynamic range to 10, the
largest (by a factor of 10) recorded so far from an SFXT. Tentative evidence
for pulsations at a period of 11.6 s is also reported. We show that these
observations challenge, for the first time, the maximum theoretical luminosity
achievable by an SFXT and propose that this giant outburst was due to the
formation of a transient accretion disc around the compact object.Comment: Accepted for publication in Astronomy and Astrophysics Letters. 5
pages, 5 figures, 2 table
Cardiovascular magnetic resonance myocardial perfusion: methods and applications in patients with coronary artery disease
Perfusion CMR is an attractive imaging modality that is becoming comparable with other clinically diagnostic tests. SPECT and PET are well clinically validated and have good accuracy for detection of significant CAD. However, these techniques have a rather low spatial resolution and are not suitable for the detection of subendocardial perfusion defect. In addition, the radiation burden, the potential for attenuation artefacts (SPECT) and the limited availability (PET) are limitations of these imaging techniques. An integrated assessment of myocardial perfusion, function and viability is feasible with CMR. In addition, compared to other clinically available imaging techniques, CMR perfusion has excellent spatial resolution and no ionising radiation exposure. However, it is not widely available and there is a need of protocol and pulse sequence standardization. Most perfusion analysis remains observer-dependent (“eyeball” analysis) or dependent on bolus dispersion (semi-quantitative analysis). Fully quantitative analysis using CMR perfusion is currently time-consuming for clinical application. Perfusion CMR is an evolving field with numerous future directions
Multimodality imaging:Bird's eye view from the European Society of Cardiology Congress 2019 Paris, August 31st-September 4th, 2019
At the European Society of Cardiology (ESC) congress of this year 2019, held in Paris from August 31st to September 4th, 4509 abstracts were presented. Of those, 414 (9%) belonged to an imaging category. Experts in echocardiography (VD), nuclear imaging (AS), cardiac computed tomography (CT) (MD) and cardiovascular magnetic resonance (CMR) (CBD), have selected the abstracts in their areas of expertise that were of most interest to them and are summarized in this bird's eye view from this ESC meeting. These abstracts were integrated by one of the Editors of the Journal (JB).Cardiolog
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