19,434 research outputs found
XMM-Newton observation of SNR J0533-7202 in the Large Magellanic Cloud
Aims. We present an X-ray study of the supernova remnant SNR J0533-7202 in
the Large Magellanic Cloud (LMC) and determine its physical characteristics
based on its X-ray emission. Methods. We observed SNR J0533-7202 with
XMM-Newton (flare-filtered exposure times of 18 ks EPIC-pn and 31 ks
EPIC-MOS1/MOS2). We produced X-ray images of the SNR, performed an X-ray
spectral analysis, and compared the results to multi-wavelength studies.
Results. The distribution of X-ray emission is highly non-uniform, with the
south-west region brighter than the north-east. The X-ray emission is
correlated with the radio emission from the remnant. We determine that this
morphology is likely due to the SNR expanding into a non-uniform ambient medium
and not an absorption effect. We estimate the size to be 53.9 (\pm 3.4) x 43.6
(\pm 3.4) pc, with the major axis rotated ~64 degrees east of north. We find no
spectral signatures of ejecta and infer that the X-ray plasma is dominated by
swept-up interstellar medium. Using the spectral fit results and the Sedov
self-similar solution, we estimate an age of ~17-27 kyr, with an initial
explosion energy of (0.09-0.83) x 10^51 erg. We detected an X-ray source
located near the centre of the remnant, namely XMMU J053348.2-720233. The
source type could not be conclusively determined due to the lack of a
multi-wavelength counterpart and low X-ray counts. We find that it is likely
either a background active galactic nucleus or a low-mass X-ray binary in the
LMC. Conclusions. We detected bright thermal X-ray emission from SNR J0533-7202
and determined that the remnant is in the Sedov phase of its evolution. The
lack of ejecta emission prohibits us from typing the remnant with the X-ray
data. Therefore, the likely Type Ia classification based on the local stellar
population and star formation history reported in the literature cannot be
improved upon.Comment: 7 pages, 4 figures, accepted for publication in Astronomy and
Astrophysic
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
Quality of Radiomic Features in Glioblastoma Multiforme: Impact of Semi-Automated Tumor Segmentation Software.
ObjectiveThe purpose of this study was to evaluate the reliability and quality of radiomic features in glioblastoma multiforme (GBM) derived from tumor volumes obtained with semi-automated tumor segmentation software.Materials and methodsMR images of 45 GBM patients (29 males, 16 females) were downloaded from The Cancer Imaging Archive, in which post-contrast T1-weighted imaging and fluid-attenuated inversion recovery MR sequences were used. Two raters independently segmented the tumors using two semi-automated segmentation tools (TumorPrism3D and 3D Slicer). Regions of interest corresponding to contrast-enhancing lesion, necrotic portions, and non-enhancing T2 high signal intensity component were segmented for each tumor. A total of 180 imaging features were extracted, and their quality was evaluated in terms of stability, normalized dynamic range (NDR), and redundancy, using intra-class correlation coefficients, cluster consensus, and Rand Statistic.ResultsOur study results showed that most of the radiomic features in GBM were highly stable. Over 90% of 180 features showed good stability (intra-class correlation coefficient [ICC] ≥ 0.8), whereas only 7 features were of poor stability (ICC < 0.5). Most first order statistics and morphometric features showed moderate-to-high NDR (4 > NDR ≥1), while above 35% of the texture features showed poor NDR (< 1). Features were shown to cluster into only 5 groups, indicating that they were highly redundant.ConclusionThe use of semi-automated software tools provided sufficiently reliable tumor segmentation and feature stability; thus helping to overcome the inherent inter-rater and intra-rater variability of user intervention. However, certain aspects of feature quality, including NDR and redundancy, need to be assessed for determination of representative signature features before further development of radiomics
Near-infrared and X-ray obscuration to the nucleus of the Seyfert 2 galaxy NGC 3281
We present the results of a near-infrared and X-ray study of the Seyfert 2
galaxy NGC 3281. Emission from the Seyfert nucleus is detected in both regions
of the electromagnetic spectrum, allowing us to infer both the equivalent line
of sight hydrogen column density, N_H = 71.0(+11.3,-12.3)e26/m^2 and the
extinction due to dust, A_V = 22+/-11 magnitudes (90% confidence intervals). We
infer a ratio of N_H/A_V which is an order of magnitude larger than that
determined along lines of sight in the Milky Way and discuss possible
interpretations. We consider the most plausible explanation to be a dense cloud
in the foreground of both the X-ray and infrared emitting regions which
obscures the entire X-ray source but only a fraction of the much larger
infrared source.Comment: 23 pages including 9 figure
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The shape of online meetings
Live videoconferencing has become an integral part of international virtual learning and working with professionals, educators and students using online meetings to enhance their collaboration from different parts of the world. This paper explores the visualization of a set of different online meetings produced by the FlashMeeting' videoconferencing system. Our polar area visualization analysis reveals interesting patterns in participant dominance in online meetings: seminars, interviews, moderated project meetings, peer-to-peer meetings, web-casts and video lectures. Visualizing patterns in the use of foreground and background communication channels is a promising way to help us to start to explore individual user roles in different communities and in different meeting types
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