Search results for "astronomía"
showing 10 items of 247 documents
Aspects of physics beyond the standard model
2021
Emprant els diferents problemes del Model Estàndar com a guia, en esta tesi presente noves teories que milloren la nostra descripció de la natura al nivell més fonamental. En la primera part, després de revisitar el Model Estàndar, enumere i descric les raons que tenim per a sospitar de l'existència d'una teoria més fonamental. La parts dos, basada en diferents articles d'investigació, es centra en les possibles connexions entre l'orige de la massa del neutrí i la natura de la matèria fosca. Finalment, a la part tres, estudie en detall teories que permeten unificar les forces i explicar els diferents números quàntics dels fermions del Model Estàndar i, a més, explicar la replicació de les f…
SHARDS: A global view of the star formation activity at z~0.84 and z~1.23
2015
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Relativistic simulations of rotational core collapse : II. Collapse dynamics and gravitational radiation
2002
We have performed hydrodynamic simulations of relativistic rotational supernova core collapse in axisymmetry and have computed the gravitational radiation emitted by such an event. Details of the methodology and of the numerical code have been given in an accompanying paper. We have simulated the evolution of 26 models in both Newtonian and relativistic gravity. Our simulations show that the three different types of rotational supernova core collapse and gravitational waveforms identified in previous Newtonian simulations (regular collapse, multiple bounce collapse, and rapid collapse) are also present in relativistic gravity. However, rotational core collapse with multiple bounces is only …
Gaia-ESO Survey: Gas dynamics in the Carina nebula through optical emission lines
2016
Aims. We present observations from the Gaia-ESO Survey in the lines of Hα, [N II], [S II], and He I of nebular emission in the central part of the Carina nebula. Methods. We investigate the properties of the two already known kinematic components (approaching and receding), which account for the bulk of emission. Moreover, we investigate the features of the much less known low-intensity high-velocity (absolute RV >50 km s) gas emission. Results. We show that gas giving rise to Hα and He I emission is dynamically well correlated with but not identical to gas seen through forbidden-line emission. Gas temperatures are derived from line-width ratios, and densities from [S II] doublet ratios. Th…
El cometa de Halley y la imagen pública de la astronomía en la prensa diaria española de principios del siglo XX
2013
Este texto pretende mostrar algunos aspectos de las representaciones formadas en la opinión pública española acerca de la astronomía y la astrofísica, a partir del análisis de las noticias publicadas en algunas de las cabeceras más destacadas con motivo de la aparición del cometa de Halley en 1910. El interés despertado por la llegada de este cometa estuvo íntimamente ligado a su asociación con diferentes desastres y calamidades, representado en este caso por el equipaje de gases mortíferos que portaba y que desató una inquietud generalizada entre una parte importante de la población. Esta preocupación sirvió para reforzar y legitimar frente a la opinión pública la actividad desarrollada po…
Measurement of hard double-parton interactions inW(???) + 2-jet events at $\sqrt{s}\,=7$ TeV with the ATLAS detector
2013
The production of W bosons in association with two jets in proton–proton collisions at a centre-of-mass energy of √s=7 TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36 pb[superscript −1], collected with the ATLAS detector at the Large Hadron Collider. The fraction of events arising from double-parton interactions, f[superscript (D) over subscript DP], has been measured through the p[subscript T] balance between the two jets and amounts to f[superscript (D) over subscript DP] = 0.08 ± 0.01 (stat.) ± 0.02 (sys.) for jets with transverse momentum p[subscript T] > 20 GeV and rapidity |y| < 2.8. This corresponds to a …
Crust-magnetosphere coupling during magnetar evolution and implications for the surface temperature
2018
We study the coupling of the force-free magnetosphere to the long-term internal evolution of a magnetar. We allow the relation between the poloidal and toroidal stream functions - that characterizes the magnetosphere - to evolve freely without constraining its particular form. We find that, on time-scales of the order of kyr, the energy stored in the magnetosphere gradually increases, as the toroidal region grows and the field lines expand outwards. This continues until a critical point is reached beyond which force-free solutions for the magnetosphere can no longer be constructed, likely leading to some large-scale magnetospheric reorganization. The energy budget available for such events …
Long-term evolution of the force-free twisted magnetosphere of a magnetar
2017
We study the long-term quasi-steady evolution of the force-free magnetosphere of a magnetar coupled to its internal magnetic field. We find that magnetospheric currents can be maintained on long timescales of the order of thousands of years. Meanwhile, the energy, helicity and twist stored in the magnetosphere all gradually increase over the course of this evolution, until a critical point is reached, beyond which a force-free magnetosphere cannot be constructed. At this point, some large-scale magnetospheric rearrangement, possibly resulting in an outburst or a flare, must occur, releasing a large fraction of the stored energy, helicity and twist. After that, the quasi-steady evolution sho…
The force-free twisted magnetosphere of a neutron star – II. Degeneracies of the Grad–Shafranov equation
2017
We extend our previous study of equilibrium solutions of non-rotating force-free magnetospheres of neutron stars. We show that multiple solutions exist for the same sets of parameters, implying that the solutions are degenerate. We are able to obtain configurations with disconnected field lines, however, in nearly all cases these correspond to degenerate higher energy solutions. We carry out a wide parametric search in order to understand the properties of the solutions. We confirm our previous results that the lower energy solutions have up to $\sim 25\%$ more energy than the vacuum case, helicity of the order of $\sim 5$ (in some defined units), maximum twist of $\sim 1.5$ rad, and a dipo…
Instability of twisted magnetar magnetospheres
2019
We present three-dimensional force-free electrodynamics simulations of magnetar magnetospheres that demonstrate the instability of certain degenerate, high energy equilibrium solutions of the Grad-Shafranov equation. This result indicates the existence of an unstable branch of twisted magnetospheric solutions and allows to formulate an instability criterion. The rearrangement of magnetic field lines as a consequence of this instability triggers the dissipation of up to 30% of the magnetospheric energy on a thin layer above the magnetar surface. During this process, we predict an increase of the mechanical stresses onto the stellar crust, which can potentially result in a global mechanical f…