Search results for "ASTROFÍSICA"
showing 10 items of 402 documents
Gravitational-Wave Astronomy: Modelling, detection, and data analysis
2017
La detección directa de la primera señal de ondas gravitatorias, el 14 de Septiembre de 2015, puede considerarse uno de los mayores hitos científicos de todos los tiempos. No solo porque supone la confirmación de la última de las predicciones de la Teoría de la Relatividad General de Albert Einstein, sino porque anticipa una autentica revolución en el campo de las astrofísica, comparable a la producida con la invención del telescopio por Galileo Galilei en 1609. Este descubrimiento ha inaugurado un nuevo tipo de astronomía, la astronomía de ondas gravitatorias. Se abre así una nueva ventana al universo que permitirá el estudio de procesos físicos producidos en regiones no accesibles al espe…
Pulsating B and Be stars in the Small Magellanic Cloud
2008
Context: Stellar pulsations in main-sequence B-type stars are driven by the kappa-mechanism due to the Fe-group opacity bump. The current models do not predict the presence of instability strips in the B spectral domain at very low metallicities. As the metallicity of the SMC is lower than Z=0.005, it constitutes a very suitable object to test these predictions. Aims: The main objective is to investigate the existence of B-type pulsators at low metallicities, searching for short-term periodic variability in absorption-line B and Be stars in the SMC. The analysis has been performed in a sample of 313 B and Be stars with fundamental astrophysical parameters accurately determined from high-res…
Numerical treatment of radiation processes in the internal shocks of magnetized relativistic outflows
2017
Los blázares son un tipo de núcleo activo de galaxia (AGN, por sus siglas en inglés) que se encuentran entre los objetos astrofísicos más energéticos y violentos, a la par de los brotes de rayos gamma (GRB por sus siglas en inglés). Los procesos físicos y, en particular, el escenario del chorro relativista en el que se genera la radiación ultraenergética detectada por observatorios terrestres y en órbita, han conseguido atraer la atención e interés de los astrónomos y astrofísicos desde su descubrimiento. En la presente tesis investigamos el modelo de choques internos (IS) cuya hipótesis consta del choque de dos capas de plasma con geometría cilíndrica, formando dos ondas de choque que atra…
Radio and infrared interferometry of stellar and substellar objects
2020
En el trabajo presentado aquí hemos usado la interferometría a modo de navaja suiza, lo cual nos ha permitido hacer contribuciones relevantes a diversos campos donde una gran resolución angular proporciona una gran ventaja. Hemos estudiado tanto objetos estelares como sub-estelares: desde gigantes rojas con atmósferas muy extensas y frías hasta enanas ultra-frías con una actividad magnética extrema. Todo gracias a la gran resolución que proporcionan los instrumentos actuales, tanto en radio como en infrarrojo, junto con su gran sensibilidad. In the work presented here, we have used interferometry as a Swiss knife allowing us to make contributions in a number of relevant astrophysical scenar…
Radio emission of binary stars in the AB Doradus moving group
2016
We present a study of the radio emission and kinematics of a sample of stars belonging to the AB Doradus moving group through VLA and VLBI observations. The main aim of our study is to obtain precise estimates of the dynamical mass of young, low-mass stars, which in combination with photometric measurements provide precise benchmarks for calibrating pre-main-sequence (PMS) stellar evolutionary models. Calibration of PMS models appears essential as they are widely used to predict the masses of low mass objects as brown dwarfs and planets. Previous studies show that model predictions are in disagreement with experimental results for masses below 1.2 solar masses. Among the stars included in o…
Near-infrarred spectro-interferometry of red giant and supergiant stars
2015
Las estrellas supergigantes rojas son estrellas frías y muy masivas que se encuentran en la fase previa a las estrellas Wolf-Rayet y a las supernovas. Presentan extensas atmósferas y fuertes vientos estelares que dan lugar a una importante pérdida de masa. El mecanismo que da lugar a estos vientos y a las extensas atmósferas es actualmente tema de debate. Además, la estimación de los parámetros fundamentales de este tipo de estrellas y su posterior localización en el diagrama HR es de gran importancia para calibrar los modelos de evolución estelar, y entender cómo la pérdida de masa afecta a su evolución. En esta tesis hemos estudiado una muestra representativa de estrellas supergigantes ro…
ALHAMBRA Ks band selected catalogue
2017
Galaxy formation and evolution are an essential part of astronomy and cosmology today. To better understand the processes that are involved in the mechanism behind them it is necessary to study the physical processes in the observable universe at different epochs, which requires large astronomical surveys. In the case of the ALHAMBRA Survey, near infrared images (NIR) provide extra information that significantly increases the scientific value of the data, particularly for strongly-reddened elliptical galaxies, AGN or moderate-redshift starburst galaxies. The selection in the optical band F814W (used for ALHAMBRA’s original catalogue in Molino et al. (2014)) creates a bias against intrinsica…
Stochastic gravito-inertial modes discovered by CoRoT in the hot Be star HD 51452
2012
International audience; Context. Be stars are rapidly rotating stars with a circumstellar decretion disk. They usually undergo pressure and/or gravity pulsation modes excited by the κ-mechanism, i.e. an effect of the opacity of iron-peak elements in the envelope of the star. In the Milky Way, p-modes are observed in stars that are hotter than or equal to the B3 spectral type, while g-modes are observed at the B2 spectral type and cooler. Aims. We observed a B0IVe star, HD 51452, with the high-precision, high-cadence photometric CoRoT satellite and high-resolution, ground-based HARPS and SOPHIE spectrographs to study its pulsations in great detail. We also used the lower resolution spectra a…
Measuring galaxy segregation with the mark connection function
2010
(abridged) The clustering properties of galaxies belonging to different luminosity ranges or having different morphological types are different. These characteristics or `marks' permit to understand the galaxy catalogs that carry all this information as realizations of marked point processes. Many attempts have been presented to quantify the dependence of the clustering of galaxies on their inner properties. The present paper summarizes methods on spatial marked statistics used in cosmology to disentangle luminosity, colour or morphological segregation and introduces a new one in this context, the mark connection function. The methods used here are the partial correlation functions, includi…
A photometric study of Be stars located in the seismology fields of COROT
2007
Context: In preparation for the COROT mission, an exhaustive photometric study of Be stars located in the seismology fields of the COROT mission has been performed. The very precise and long-time-spanned photometric observations gathered by the COROT satellite will give important clues of the origin of the Be phenomenon. Aims: The aim of this work is to find short-period variable Be stars located in the seismology fields of COROT and to study and characterise their pulsational properties. Methods: Light curves obtained at the Observatorio de Sierra Nevada together with data from Hipparcos and ASAS-3 of a total of 84 Be stars have been analysed in order to search for short-term variations. W…