Search results for " objects"

Unveiling the spatial structure of the overionized plasma in the supernova remnant W49B

2011

W49B is a mixed-morphology supernova remnant with thermal X-ray emission dominated by the ejecta. In this remnant, the presence of overionized plasma has been directly established, with information about its spatial structure. However, the physical origin of the overionized plasma in W49B has not yet been understood. We investigate this intriguing issue through a 2D hydrodynamic model that takes into account, for the first time, the mixing of ejecta with the inhomogeneous circumstellar and interstellar medium, the thermal conduction, the radiative losses from optically thin plasma, and the deviations from equilibrium of ionization induced by plasma dynamics. The model was set up on the basi…

Unveiling pure-metal ejecta X-ray emission in supernova remnants through their radiative recombination continuum

2020

Spectral analysis of X-ray emission from ejecta in supernova remnants (SNRs) is hampered by the low spectral resolution of CCD cameras, which creates a degeneracy between the best-fit values of abundances and emission measure. The combined contribution of shocked ambient medium and ejecta to the X-ray emission complicates the determination of the ejecta mass and chemical composition, leading to big uncertainties in mass estimates and it can introduce a bias in the comparison between the observed ejecta composition and the yields predicted by explosive nucleosynthesis. We explore the capabilities of present and future spectral instruments with the aim of identifying a spectral feature which …

Spatial distribution of X-ray emitting ejecta in Tychos SNR: indications of shocked Titanium

2015

Young supernova remnants show a characteristic ejecta-dominated X-ray emission that allows us to probe the products of the explosive nucleosynthesis processes and to ascertain important information about the physics of the supernova explosions. Hard X-ray observations have recently revealed the radioactive decay lines of 44Ti at ~67.9 keV and ~78.4 keV in the Tycho's SNR. We here analyze the set of XMM-Newton archive observations of the Tycho's SNR. We produce equivalent width maps of the Fe K and Ca XIX emission lines and find indications for a stratification of the abundances of these elements and significant anisotropies. We then perform a spatially resolved spectral analysis by identify…

Born–Infeld inspired modifications of gravity

2017

General Relativity has shown an outstanding observational success in the scales where it has been directly tested. However, modifications have been intensively explored in the regimes where it seems either incomplete or signals its own limit of validity. In particular, the breakdown of unitarity near the Planck scale strongly suggests that General Relativity needs to be modified at high energies and quantum gravity effects are expected to be important. This is related to the existence of spacetime singularities when the solutions of General Relativity are extrapolated to regimes where curvatures are large. In this sense, Born-Infeld inspired modifications of gravity have shown an extraordin…

Highlights from the ARGO-YBJ Experiment

2012

""The ARGO-YBJ experiment at YangBaJing in Tibet (4300m a.s.l.) has been taking data with its full layout since October 2007. Here we present a few significant results obtained in gamma-ray astronomy and cosmic-ray physics. Emphasis is placed on the analysis of gamma-ray emission from point-like sources (Crab Nebula, MRK 421), on the preliminary limit on the antiproton\\\/proton flux ratio, on the large-scale cosmic-ray anisotropy and on the proton-air cross-section. The performance of the detector is also discussed, and the perspectives of the experiment are outlined.""

Print and online newspapers as material artefacts

2014

Traditional newspaper journalism is in a state of crisis and there have been several attempts to overcome this. Many discourses have reiterated the triumphal march of a digital revolution in newspaper journalism and anticipated the end of the print newspaper. This moment calls for an in-depth analysis of reader habits of news consumption and use in order to understand the audiences for journalistic output and their relationship with the journalistic objects. In this study, we adopt a multi-method approach, integrating (1) qualitative content analysis of student essays dealing with the physicality of printed and online newspapers, (2) ethnographic observation of the use practices of readers…

X-ray Emission Mechanisms in Herbig - Haro objects .

2006

Negative and positive feedback from a supernova remnant with SHREC

2022

Supernova remnants (SNRs) contribute to regulate the star formation efficiency and evolution of galaxies. As they expand into the interstellar medium (ISM), they transfer vast amounts of energy and momentum that displace, compress and heat the surrounding material. Despite the extensive work in galaxy evolution models, it remains to be observationally validated to what extent the molecular ISM is affected by the interaction with SNRs. We use the first results of the ESO-ARO Public Spectroscopic Survey SHREC, to investigate the shock interaction between the SNR IC443 and the nearby molecular clump G. We use high sensitivity SiO(2-1) and H$^{13}$CO$^+$(1-0) maps obtained by SHREC together wit…

Modeling the mixed-morphology supernova remnant IC 443. Origin of its complex morphology and X-ray emission

2020

The morphology and the distribution of material observed in SNRs reflect the interaction of the SN blast wave with the ambient environment, the physical processes associated with the SN explosion and the internal structure of the progenitor star. IC 443 is a MM SNR located in a quite complex environment: it interacts with a molecular cloud in the NW and SE areas and with an atomic cloud in the NE. In this work we aim at investigating the origin of the complex morphology and multi-thermal X-ray emission observed in SNR IC 443, through the study of the effect of the inhomogeneous ambient medium in shaping its observed structure, and the exploration of the main parameters characterizing the re…

Novel Indexing Method of Relations Between Salient Objects

2011

Since the last decade, images have been integrated into several application domains such as GIS, medicine, etc. This integration necessitates new managing methods particularly in image retrieval. Queries should be formulated using different types of features such as low-level features of images (histograms, color distribution, etc.), spatial and temporal relations between salient objects, semantic features, etc. In this chapter, we propose a novel method for identifying and indexing several types of relations between salient objects. Spatial relations are used here to show how our method can provide high expressive power to relations in comparison to the traditional methods.