17 resultados para Clararrosa, José Joaquín de
em Universidad de Alicante
Resumo:
El presente trabajo es resultado de un proyecto correspondiente a ediciones anteriores del programa Redes, que permitió la creación de un repositorio virtual que albergue el material elaborado por los profesores de las asignaturas de Física en las titulaciones de Grado. Actualmente, y debido a la motivación de los participantes, se está trabajando en poner al día el material correspondiente a los Grados y ampliarlo a las asignaturas Máster orientados a las tecnologías que se imparten en la Escuela Politécnica Superior de la Universidad de Alicante. El material recopilado es accesible virtualmente por todo el profesorado del departamento implicado en las asignaturas de Física, por medio de un repositorio virtual. Por otro lado, terminada una primera parte del trabajo nos encontramos inmersos en una reflexión sobre las metodologías aplicadas a partir del diálogo y la discusión entre los docentes sobre la experiencia en el aula con los alumnos y con los materiales generados.
Resumo:
Context. We report the infrared identification of the X-ray source 2XMM J191043.4+091629.4, which was detected by XMM-Newton/EPIC in the vicinity of the Galactic supernova remnant W49B. Aims. The aim of this work is to establish the nature of the X-ray source 2XMM J191043.4+091629.4 studying both the infrared photometry and spectroscopy of the companion. Methods. We analysed UKIDSS images around the best position of the X-ray source and obtained spectra of the best candidate using NICS in the Telescopio Nazionale Galileo (TNG) 3.5-m telescope. We present photometric and spectroscopic TNG analyses of the infrared counterpart of the X-ray source, identifying emission lines in the K-band. The H-band spectra does not present any significant feature. Results. We have shown that the Brackett γ H i at 2.165 μm, and He i at 2.184 μm and at 2.058 μm are significantly present in the infrared spectrum. The CO bands are also absent from our spectrum. Based on these results and the X-ray characteristics of the source, we conclude that the infrared counterpart is an early B-type supergiant star with an E(B − V) = 7.6 ± 0.3 at a distance of 16.0 ± 0.5 kpc. This would be, therefore, the first high-mass X-ray binary in the Outer Arm at galactic longitudes of between 30° and 60°.
Resumo:
We present an analysis of a series of four consecutive Chandra high-resolution transmission gratings observations, amounting to a total of 150 ks, of the Be X-ray source HD 119682 (=1WGA J1346.5–6255), a member of the new class of γ Cas analogs. The Chandra light curve shows significant brightness variations on timescales of hours. However, the spectral distribution appears rather stable within each observation and during the whole campaign. A detailed analysis is not able to detect any coherent pulsation up to a frequency of 0.05 Hz. The Chandra High Energy Transmission Gratings spectrum seems to be devoid of any strong emission line, including Fe Kα fluorescence. The continuum is well described with the addition of two collisionally ionized plasmas of temperatures kT ≈ 15 keV and 0.2 keV, respectively, by the apec model. Models using photoionized plasma components (mekal) or non-thermal components (powerlaw) give poorer fits, providing support for the pure thermal scenario. These two components are absorbed by a single column with N H = (0.20+0.15 –0.03) × 1022 cm–2 compatible with the interstellar value. We conclude that HD 119682 can be regarded as a pole-on γ Cas analog.
Resumo:
We present analysis of 100 ks contiguous XMM-Newton data of the prototypical wind accretor Vela X-1. The observation covered eclipse egress between orbital phases 0.134 and 0.265, during which a giant flare took place, enabling us to study the spectral properties both outside and during the flare. This giant flare with a peak luminosity of 3.92+0.42-0.09 × 1037 erg s-1 allows estimates of the physical parameters of the accreted structure with a mass of ~1021 g. We have been able to model several contributions to the observed spectrum with a phenomenological model formed by three absorbed power laws plus three emission lines. After analysing the variations with orbital phase of the column density of each component, as well as those in the Fe and Ni fluorescence lines, we provide a physical interpretation for each spectral component. Meanwhile, the first two components are two aspects of the principal accretion component from the surface of the neutron star, the third component seems to be the X-ray light echo formed in the stellar wind of the companion.
Resumo:
High resolution X-ray spectroscopy is a powerful tool for studying the nature of the matter surrounding the neutron star in X-ray binaries and its interaction between the stellar wind and the compact object. In particular, absorption features in their spectra could reveal the presence of atmospheres of the neutron star or their magnetic field strength. Here we present an investigation of the absorption feature at 2.1 keV in the X-ray spectrum of the high mass X-ray binary 4U 1538–52 based on our previous analysis of the XMM-Newton data. We study various possible origins and discuss the different physical scenarios in order to explain this feature. A likely interpretation is that the feature is associated with atomic transitions in an O/Ne neutron star atmosphere or of hydrogen and helium like Fe or Si ions formed in the stellar wind of the donor.
Resumo:
Cuando finalice el curso 2013-14 se producirá la salida de la primera promoción de graduados en la Escuela Politécnica Superior (EPS). Teniendo en cuenta que antes de que transcurran seis años se debe renovar la acreditación de los títulos oficiales de Grado, consideramos adecuado efectuar un análisis crítico del proceso de enseñanza-aprendizaje. En este trabajo presentamos los resultados del seguimiento realizado en el contexto educativo de los fundamentos físicos en los títulos de grado de la EPS. Estos resultados muestran la necesidad de abordar los cambios necesarios para corregir las deficiencias detectadas y mejorar la calidad del aprendizaje. Conviene recordar que el cambio que se pretendía realizar en la enseñanza universitaria era para centrarse en el aprendizaje del alumnado. Además incluimos un estudio de la evolución del aprendizaje de la física analizando las calificaciones de acceso en física y matemáticas y comparándolas con las obtenidas en los fundamentos físicos de los diferentes grados impartidos en la EPS. También presentaremos buena parte de las actividades realizadas para facilitar el aprendizaje continuo de nuestro alumnado mediante el uso de nuevas herramientas informáticas, como blogs, OpenCourseWare, materiales audiovisuales (pUAs), etc.
Resumo:
Numerosos estudios han puesto de manifiesto la dificultad del aprendizaje de la física tanto en la educación secundaria y bachillerato como en la educación universitaria. El espacio Europeo de Educación Superior (EEES) pone énfasis en el aprendizaje del alumnado y modifica el rol del profesorado como tutor de su aprendizaje, potenciando la adquisición de los conocimientos mediante metodologías activas. Nosotros nos centraremos en desarrollar competencias transversales y favorecer un aprendizaje interactivo y global. Por ejemplo, se potenciará la búsqueda de información relacionada con un tema, se provocará la reacción o participación del alumnado sobre aspectos de aplicación de los fundamentos físicos en la edificación y en la ingeniería, se comprobará mediante la autoevaluación la adquisición de los objetivos, se favorecerá el aprendizaje atemporal, etc. También proporcionará el trabajo de algunas capacidades como la planificación de las tareas, la comunicación y exposición de ideas sobre aspectos académicos o profesionales, la generación de nuevas ideas o la construcción de conocimiento a partir de sus aportaciones. Finalmente se recogerán los comentarios y sugerencias del alumnado para adaptar los materiales diseñados a sus necesidades.
Resumo:
We present a comprehensive analysis of the whole sample of available XMM-Newton observations of high-mass X-ray binaries (HMXBs) until August 2013, focusing on the FeKα emission line. This line is key to better understanding the physical properties of the material surrounding the X-ray source within a few stellar radii (the circumstellar medium). We collected observations from 46 HMXBs and detected FeKα in 21 of them. We used the standard classification of HMXBs to divide the sample into different groups. We find that (1) different classes of HMXBs display different qualitative behaviours in the FeKα spectral region. This is visible especially in SGXBs (showing ubiquitous Fe fluorescence but not recombination Fe lines) and in γ Cass analogues (showing both fluorescent and recombination Fe lines). (2) FeKα is centred at a mean value of 6.42 keV. Considering the instrumental and fits uncertainties, this value is compatible with ionization states that are lower than Fe xviii. (3) The flux of the continuum is well correlated with the flux of the line, as expected. Eclipse observations show that the Fe fluorescence emission comes from an extended region surrounding the X-ray source. (4) We observe an inverse correlation between the X-ray luminosity and the equivalent width of FeKα (EW). This phenomenon is known as the X-ray Baldwin effect. (5) FeKα is narrow (σline< 0.15 keV), reflecting that the reprocessing material does not move at high speeds. We attempt to explain the broadness of the line in terms of three possible broadening phenomena: line blending, Compton scattering, and Doppler shifts (with velocities of the reprocessing material V ~ 1000 km s-1). (6) The equivalent hydrogen column (NH) directly correlates to the EW of FeKα, displaying clear similarities to numerical simulations. It highlights the strong link between the absorbing and the fluorescent matter. (7) The observed NH in supergiant X-ray binaries (SGXBs) is in general higher than in supergiant fast X-ray transients (SFXTs). We suggest two possible explanations: different orbital configurations or a different interaction compact object – wind. (8) Finally, we analysed the sources IGR J16320-4751 and 4U 1700-37 in more detail, covering several orbital phases. The observed variation in NH between phases is compatible with the absorption produced by the wind of their optical companions. The results clearly point to a very important contribution of the donor’s wind in the FeKα emission and the absorption when the donor is a supergiant massive star.
Resumo:
Context. 4U 1538−52, an absorbed high mass X-ray binary with an orbital period of ~3.73 days, shows moderate orbital intensity modulations with a low level of counts during the eclipse. Several models have been proposed to explain the accretion at different orbital phases by a spherically symmetric stellar wind from the companion. Aims. The aim of this work is to study both the light curve and orbital phase spectroscopy of this source in the long term. In particular, we study the folded light curve and the changes in the spectral parameters with orbital phase to analyse the stellar wind of QV Nor, the mass donor of this binary system. Methods. We used all the observations made from the Gas Slit Camera on board MAXI of 4U 1538−52 covering many orbits continuously. We obtained the good interval times for all orbital phase ranges, which were the input for extracting our data. We estimated the orbital period of the system and then folded the light curves, and we fitted the X-ray spectra with the same model for every orbital phase spectrum. We also extracted the averaged spectrum of all the MAXI data available. Results. The MAXI spectra in the 2–20 keV energy range were fitted with an absorbed Comptonisation of cool photons on hot electrons. We found a strong orbital dependence of the absorption column density but neither the fluorescence iron emission line nor low energy excess were needed to fit the MAXI spectra. The variation in the spectral parameters over the binary orbit were used to examine the mode of accretion onto the neutron star in 4U 1538−52. We deduce a best value of Ṁ/v∞ = 0.65 × 10-9M⊙ yr-1/ (km s-1) for QV Nor.
Resumo:
We present an analysis of a 78 ks Chandra high-energy transmission gratings observation of the B0I star QV Nor, the massive donor of the wind-accreting pulsar 4U1538−52. The neutron star (NS) orbits its companion in a very close orbit (r < 1.4R*, in units of the stellar radii), thereby allowing probing of the innermost wind regions. The flux of the Fe Kα line during eclipse reduces to only ∼30% of the flux measured out of eclipse. This indicates that the majority of Fe fluorescence must be produced in regions close to the NS, at distances smaller than 1R* from its surface. The fact that the flux of the continuum decreases to only ∼3% during eclipse allows for a high contrast of the Fe Kα line fluorescence during eclipse. The line is not resolved and centered at 1.9368 0.0018 l = 0.0032 - + Å. From the inferred plasma speed limit of v < c l < 800 l D km s−1 and range of ionization parameters of log 1, 2 x = [- ], together with the stellar density profile, we constrain the location of the cold, dense material in the stellar wind of QV Nor using simple geometrical considerations. We then use the Fe Kα line fluorescence as a tracer of wind clumps and determine that these clumps in the stellar wind of QV Nor (B0I) must already be present at radii r < 1.25R*, close to the photosphere of the star.
Resumo:
La preparación previa del alumnado que cursa la asignatura de Fundamentos Físicos en primer curso de grado implantado en la Escuela Politécnica Superior de la Universidad de Alicante, es muy heterogénea. Además, se da la circunstancia que en los últimos cursos alrededor de un 50% del alumnado no ha cursado nunca una asignatura de física anteriormente, aunque esta situación depende del grado concreto. En este trabajo presentamos un análisis de los resultados obtenidos en el curso 14-15 en dos grupos teóricos de Fundamentos Físicos de la Informática a lo largo del curso. Nuestro objetivo es mejorar la metodología de la asignatura en actividades como cursos de iniciación, distribución homogénea del alumnado en los grupos teóricos, o adaptación de la guía docente al contexto particular de cada grupo. Otro aspecto que trabaja la red es el desarrollo de materiales para el autoaprendizaje de la física. Nuestro objetivo es facilitar que el alumnado pueda prepararse la asignatura de Fundamentos Físicos utilizando estos materiales. Entre ellos destacamos la elaboración de libros de resolución de problemas y la elaboración de blogs educativos.
Resumo:
Para la realización de este trabajo, Antonio Escudero y Salvador Salort se han beneficiado del proyecto de investigación del Ministerio de Economía y Competitividad HAR 2010-21941-C03-01.
Resumo:
Dentro de las investigaciones sobre psicología del testimonio destaca, por el volumen de trabajos, el área de la identificación de personas. En este artículo se pretende dar una visión global de los diferentes procedimientos de identificación, aportando datos para juzgar su utilidad cuando son empleados por testigos para reconocer o recordar a una persona. Se sugiere que los errores de los testigos pueden ser interpretados al entender el funcionamiento de la memoria más como reconstrucción que como reproducción de sucesos, sugiriéndose como más conveniente para la interpretación de los datos actuales la teoría de conocimiento social de Nisbett y Ross (1980). Se aporta, también, una extensa bibliografía sobre este tema.
Resumo:
Context. Classical supergiant X-ray binaries (SGXBs) and supergiant fast X-ray transients (SFXTs) are two types of high-mass X-ray binaries (HMXBs) that present similar donors but, at the same time, show very different behavior in the X-rays. The reason for this dichotomy of wind-fed HMXBs is still a matter of debate. Among the several explanations that have been proposed, some of them invoke specific stellar wind properties of the donor stars. Only dedicated empiric analysis of the donors’ stellar wind can provide the required information to accomplish an adequate test of these theories. However, such analyses are scarce. Aims. To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J17544-2619 (SFXT) and Vela X-1 (SGXB). We analyze the spectra of each star in detail and derive their stellar and wind properties. As a next step, we compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. Methods. We use archival infrared, optical and ultraviolet observations, and analyze them with the non-local thermodynamic equilibrium (NLTE) Potsdam Wolf-Rayet model atmosphere code. We derive the physical properties of the stars and their stellar winds, accounting for the influence of X-rays on the stellar winds. Results. We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). The distance to the sources have been revised and also agree well with the estimations already available in the literature. In IGR J17544-2619 we are able to narrow the uncertainty to d = 3.0 ± 0.2 kpc. From the stellar radius of the donor and its X-ray behavior, the eccentricity of IGR J17544-2619 is constrained to e< 0.25. The derived chemical abundances point to certain mixing during the lifetime of the donors. An important difference between the stellar winds of the two stars is their terminal velocities (ν∞ = 1500 km s-1 in IGR J17544-2619 and ν∞ = 700 km s-1 in Vela X-1), which have important consequences on the X-ray luminosity of these sources. Conclusions. The donors of IGR J17544-2619 and Vela X-1 have similar spectral types as well as similar parameters that physically characterize them and their spectra. In addition, the orbital parameters of the systems are similar too, with a nearly circular orbit and short orbital period. However, they show moderate differences in their stellar wind velocity and the spin period of their neutron star which has a strong impact on the X-ray luminosity of the sources. This specific combination of wind speed and pulsar spin favors an accretion regime with a persistently high luminosity in Vela X-1, while it favors an inhibiting accretion mechanism in IGR J17544-2619. Our study demonstrates that the relative wind velocity is critical in class determination for the HMXBs hosting a supergiant donor, given that it may shift the accretion mechanism from direct accretion to propeller regimes when combined with other parameters.