Search results for "CCR"
showing 10 items of 574 documents
Unveiling the disc structure in ultraluminous X-ray source NGC 55 ULX-1
2022
Ultraluminous X-ray sources (ULXs) are the most extreme among X-ray binaries in which the compact object, a neutron star or a black hole, accretes matter from the companion star, and exceeds a luminosity of 1039 ergs−1 in the X-ray energy band alone. Despite two decades of studies, it is still not clear whether ULX spectral transitions are due to stochastic variability in the wind or variations in the accretion rate or in the source geometry. The compact object is also unknown for most ULXs. In order to place constraints on to such scenarios and on the structure of the accretion disc, we studied the temporal evolution of the spectral components of the variable source NGC 55 ULX-1. Using rec…
Broadband spectral analysis of MXB 1659-298 in its soft and hard state
2019
The X-ray transient eclipsing source MXB 1659-298 went in outburst in 1999 and 2015, respectively, during which it was observed by XMM-Newton, NuSTAR and Swift. Using these observations we studied the broadband spectrum of the source to constrain the continuum components and to verify the presence of a reflection component. We analysed the soft and hard state of the source, finding that the soft state can be modelled with a thermal component associated with the inner accretion disc plus a Comptonised component. A smeared reflection component and the presence of an ionised absorber are also requested in the best-fit model. On the other hand, the direct continuum emission in the hard state ca…
MAXI J1957+032: a new accreting millisecond X-ray pulsar in an ultra-compact binary
2022
The detection of coherent X-ray pulsations at ~314 Hz (3.2 ms) classifies MAXI J1957+032 as a fast-rotating, accreting neutron star. We present the temporal and spectral analysis performed using NICER observations collected during the latest outburst of the source. Doppler modulation of the X-ray pulsation revealed the ultra-compact nature of the binary system characterised by an orbital period of ~1 hour and a projected semi-major axis of 14 lt-ms. The neutron star binary mass function suggests a minimum donor mass of 1.7e-2 Msun, assuming a neutron star mass of 1.4 Msun and a binary inclination angle lower than 60 degrees. This assumption is supported by the lack of eclipses or dips in th…
La praxis de la excelencia universitaria entre la paranoia de sus promotores y la culpa de sus víctimas: hacia la recuperación del deseo docente y la…
2017
Hasta 2015 la universidad de Valencia era la única universidad pública en el Estado espa- ñol que no había aprobado el programa Docentia. Dicho programa apareció en 2006, en el escenario de la integración del sistema universitario español en el Espacio Europ eo de Educación Superior (EEES). La Agencia Nacional de la Evaluación de la Calidad y Acreditación (ANECA) propu-so/impuso al conjunto de las universidades públicas españolas un nuevo programa que desde la apli- cación de los criterios de la razón neoliberal (Dardot & Laval; 2013) perseguía controlar y gestionar, en términos básicamente empresariales, la actividad docente. Este trabajo sitúa dicho programa en el proceso de mercantilizac…
Rethinking the role of Higher Education
2013
The market has to change as our current society becomes increasingly diverse and so do workers’ competences, which are now more and more cross-disciplinary. New training models have appeared seeking to meet such market and society needs. This editorial reflects on the pressing need to redefine university education and the accreditation processes in non-formal education. En el contexto actual en el que cada vez la sociedad es más plural, las necesidades del mercado cambiantes y las competencias que se requieren a los trabajadores más tranversales, aparecen nuevas modalidades de formación, modalidades asociadas a las necesidades del mercado y al interés de las personas. Este editorial reflexi…
The Changing Role of the State in French Higher Education: From Curriculum Control to Programme Accreditation
2004
The French higher education system is currently undergoing deep changes in relation to degree structure and accreditation process. In the wake of the Bologna declaration, new state regulations have been introduced since 2000 that aimed at building a degree structure that is common to all higher education institutions. As their implementation will be phased in step by step until 2006, a study of the accreditation processes in operation in France must present both past and future schemes.
Temperature dependence of sodium and ionized calcium resonance lines perturbed by helium
2014
International audience; Traces of heavy metals in cool DZ white dwarf stars may be attributed to the accretion of circumstellar dust thought to originate from tidal disruption of rocky parent bodies. Spectra of such stars therefore provide a unique opportunity to study the composition of extrasolar planetary systems. The determination of metal abundances from stellar spectra depends on stellar atmospheric parameters and an accurate prior knowledge of the collision broadening of the line profiles by the most common constituents of the stellar atmosphere. For this purpose, we present theoretical absorption spectra of Na and Ca+ broadened by He for the conditions prevailing in cool white dwarf…
<em>Veedors, marquejadors</em>, maestros: el valor de la experiencia en la carpintería medieval. El ejemplo valenciano
2014
In the carpenter’s guild of Valencia in the Middle Ages, experience and skill were two notions captured in the more comprehensive idea of expertise. The appreciation of this added value made the expert an indispensable figure inside the guild. He was present in the different positions of control and inspection established by by-laws, which ensured the quality of goods manufactured, the proper level of teaching, and the accreditation of new masters. This figure also acted as an expert assessor, estimating the work of a colleague of even assessing the value of his interventions. In this article we examine the notion of expert in medieval carpentry and the infl uence of his practical applicati…
Nucleation and accretion of bioelastomeric fibers at biological temperatures and low concentrations.
1988
Quasi-elastic light scattering (QELS) studies are reported, which address the early stages of aggregation of the polypentamer poly(VPGVG). This reflects the major primary structural feature of native elastin. The study is focused on the region of the phase diagram which in both its temperature and concentration range is closest to the state of affairs occurring in the course of bioelastogenesis by progressive synthesis of the precursor protein. Results here reported allow for the first time a self-consistent view of the physics of elastogenesis, and specify the role of the region of metastability and of that of instability of the phase diagram in the non-chaotic, orderly formation of elasto…
Long-term X-ray variability of the microquasar system LS 5039/RX J1826.2−1450
2003
We report on the results of the spectral and timing analysis of a BeppoSAX observation of the microquasar system LS 5039/RX J1826.2-1450. The source was found in a low-flux state with Fx(1-10 keV)= 4.7 x 10^{-12} erg cm^{-2} s^{-1}, which represents almost one order of magnitude lower than a previous RXTE observation 2.5 years before. The 0.1--10 keV spectrum is described by an absorbed power-law continuum with photon-number spectral index Gamma=1.8+-0.2 and hydrogen column density of NH=1.0^{+0.4}_{-0.3} x 10^{22} cm^{-2}. According to the orbital parameters of the system the BeppoSAX observation covers the time of an X-ray eclipse should one occur. However, the 1.6-10 keV light curve does…