ASTRONOMY AND ASTROPHYSICS

Author: BADENES MONTOLIU CARLES.
Year: 2003.
University: POLITÉCNICA DE CATALUÑA [More theses of this university] [www.upc.edu].
Place of defense: aula teleensenyament mòdul B-3 cn..
Place of preparation: EDIFICI B5 DESPATX 111C Campus NORD.

Author: GIAMMANCO CORRADO.
Year: 2004.
University: LA LAGUNA [More theses of this university] [www.ull.es].
Place of defense: UNIVERSIDAD DE LA LAGUNA.
Place of preparation: INSTITUTO DE ASTROFISICA DE CANARIAS.

Summary: Problems related to the inhomogeneidad in density of giant HII regions, and its impact on the loss of photons Lyman, feel the starting point of this thesis. In it, first, we conducted a statistical model for regions HII inhomogéneas. Then we compare the predictions of the models with data in different diagrams for diagnosis, while providing the necessary mathematical tool. In general, analyzing diagnostic diagrams, notes that the effect of the loss of photons by Lyman regions translates into an increase of ionization parameter estimated. So it is possible to determine the percentage of photons Lyman lost, comparing the parameter ioniazción estimated in H-alpha brightness of the region under consideration. A direct consequence of the model we propose is also the presence within regions of a significant fraction of neutral mass. Finally, move the assumption that cosmic rays in the regions themselves ionicen this mass leading to temperature fluctuations that occur in them.

Author: SERICHOL AUGUE NURIA.
Year: 2004.
University: POLITÉCNICA DE CATALUÑA [More theses of this university] [www.upc.edu].
Place of defense: Aula de Teleensenyament..
Place of preparation: Edifici B5 DESPATX: 210A NORD.

Author: GRIGAHCÈNE AHMED.
Year: 2004.
University: GRANADA [More theses of this university] [www.ugr.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: INSTITUTO DE ASTROFÍSICA Y ANDALUCIA.

Summary: This thesis explores the interplay between convection and the oscillation in the field of astrosismologia. In fact such a study is necessary because the disadvantages of convection approximation frozen until now mainly used to predict the edge of the red band volatility of the delta Scuti stars and explain the mechanism of excitation of the stars gamma Doradus. This work arose in anticipation of the space mission COROT (scheduled for 2006) of which are expected observational data much more accurate than those that are available on earth. Therefore it has become necessary substantial improvements theoretical tool that can allow the modeling of these future data. The identification of the modes of oscillation stellar remains the top target astroseismology as well as heliosísmología. Many efforts have been devoted in order to achieve this, as has been the recent improvement in the treatment of rotation. Among other things, the convection is still an outstanding problem, as a method of transporting energy so far lacks accurate analytical formulation. This is a source of considerable disagreement. The method of mixing length remains, with its different variants, the only one in force. An improved treatment of convection as a means of transporting energy, it means not only the improvement of the internal structure models in stellar astrophysics, but also improving the understanding of a phenomenon that has its applications from a pan of boiling water until the explosion of a supernova. On the other hand, the interaction between the convection with the stellar oscillations also produces another source of disagreement. The propagation of a wave in an environment that suffers a movement led by the turbulent convection is very different from its spread in an environment that does not suffer. Bear in mind that interaction allows the improvement of the calculations. Some early estimates put enable improved results within an order of magnitude of between 10 up to 15%. What is much bigger than the uncertainties in the observations. The issue touches almost most of the stars except those that are highly evolved in such a way that they do not have a wrapper convecting. We have studied the influence of convection in the stellar spectrum pulse not only through the treatment of convection as was done until now, but rather to explore the interaction convección-oscilación. We establish the principle analytical formulation of the problem as broad as possible to allow inclusion of non - radial oscillations. As a starting point taken equations that govern the structure and evolution stellar continuity equation. Equation of motion. Equation energy conservation. Equation energy transmission. Conjugadas with the equation of state. It introduces a disturbance in this set of equations. It then provides a set of equations that describe the interaction between convection and swings. This enabled us to get some very important results: obtaining the red edge of the band of instability of the delta Scuti stars for radio and non-radio modes, the explanation of the mechanism of excitation of the newly discovered stars gamma Doradus. So better not insignificant in the notes they photometric which allowed us to identify the modes of oscillation of stars 28 And and gamma Doradus.

Author: SICILIA AGUILAR MARIA AURORA.
Year: 2004.
University: AUTÓNOMA DE MADRID [More theses of this university] [www.uam.es].
Place of defense: AUTONOMA DE MADRID.
Place of preparation: UNIVERSIDAD AUTONOMA DE MADRID HARVARD SMITHSONIAN CENTER FOR ASTROPHYSICS.

Summary: This work includes the study of populations of young stars and their disks protoplanetarios, aged between 1 and 10 million years ago, belonging to the stage at which the disks circumestelares are dissipated, probably after forming planetary systems. The time between 3 and 10 million years ago is of particular interest because, due to the absence of cumulus and nearby regions in this age range, there is a lack of systematic data on the processes taking place on disks during the same. The new generation of instruments, which include the espectrógrafos multifibra Hectospec and Hectochelle, operating in the telescope 6.5m MMT (Multiple Mirror Telescope, Mount Hopkins, Arizona), and the Spitzer Space Telescope, have recently opened a new window for the investigation of these more remote regions. This study is part of a program to chart the evolution of disks protoplanetarios during the crucial stages (from 1 to 10 million years) to understand the processes that lead to the dissipation of the disks and the formation of planetary systems. First, we present the results of the observations in optical wavelengths and JHK into two piles youth in the Association of Cep OB2: Tr 37 (which is embedded in the H II region CI 1396), and NGC 7160. Using optical spectra taken with the low-resolution spectrograph Hectospec, has identified a total of about 165 and about 50 stars of low mass belonging to Tr 37 and NGC 7160, respectively (using the line of Li to 6707 Angstroms and issuing H - alpha). The fraction of low-mass stars with accretion disks is 43% Tr 37, while only a star in NGC 7160 presents indicators increase asset. The photometry in the optical, together with the corresponding theoretical isocronas allows estimating ages Tr 37 and NGC 7160, 4 and 12 million years, respectively. The presence of disks protoplanetarios in Cep OB2 is inferred through the data Spitzer, belonging to a program with Time Observation Guaranteed (GTO) to study the evolution of disks. The comments of Spitzer (IRAC and MIPS, 3.6-24.0 microns) to determine the presence and characteristics of the discs in the range of distances of about 0.1 to 20 astronomical units. The colors in the IR and spectral energy distributions (SEDs) from the low mass stars (types spectral G-M2) are presented and described, as compared with those of younger regions. The main difference between Tr 37 and Taurus is that the excesses of color wavelengths less than or equal to 5.8 microns are substantially lower in Tr 37. According to the model disks, the effect suggests that the most internal disk has suffered a major agglomeration of dust, and / or a major settlement in the same plane after 4 billion years. After 12 million years (NGC 7160), the effect of the coagulation and settling dust is even more evident in the remaining disks, hampered the issuance between 3.6 and 24.0 microns. These observations suggest, then, that the evolution of the disk starts on the inside of it, spreading outwards. It has also found a small fraction of "transitional objects" consisting of stars that are not acretando, no emission of the inner part of the disk, but still preserve the most external disk (detectable as an excess at wavelengths of 5.8 microns or longer). The shortage of these objects suggests that their lifetime are of the order of hundreds of thousands of years at most, then the external disk not 8 tardarí 2d9 to dissipate once in the internal disk has disappeared or been agglomerate.

Author: GARCÍA GIL ALEJANDRO M..
Year: 2005.
University: LA LAGUNA [More theses of this university] [www.ull.es].
Place of defense: FACULTAD DE FÍSICA.
Place of preparation: FACULTAD DE FÍSICA/INSTITUTO DE ASTROFISICA DE CANARIAS.

Summary: This thesis presents a pooled analysis of the spectra ultraviolet, optical and near-infrared of the stars Vega and Portion. For the analysis is done using atmospheric models planoparalelos in local thermodynamic equilibrium, with the so-called effect of line-blanketing and approximate length of mixture for convection, and also in non-equilibrium models termodinámico locally. Since they get physical parameters for these stars, such as effective temperature, the angular diameter of the star, and the abundances of certain chemicals, such as C, N, O, Si, Mg and Fe. For the determination of these abundances are used both the classical approach based on the stellar absorption lines as a new method developed in this thesis, where abundances are obtained from continuous adjustments to UV. The parameters obtained are compared well with the results of the literature for these objects, and discussed discrepancies encountered and how to proceed in the future to resolve them. Finally an improvement in the analysis of Vega, a rotora fast, is considered in this work. Having found distorisión of the stellar surface due to the high speed rotation obtained new parameters for Vega, which differ significantly with those obtained previously indicating the need for this type of analysis when the precise parameters of a rotora rapid want to be identified.

Author: de Hoyos Fernández de Córdova. Carlos.
Year: 2005.
University: AUTÓNOMA DE MADRID [More theses of this university] [www.uam.es].
Place of defense: Facultad de Ciencias. U.A.M..
Place of preparation: DpTO. de Fisica Teórica. U.A.M..

Summary: This dissertation is about the nature of the Compact Galaxies Bright and Blue (GLCA) to travel more parecidasa the red intermediate HII galaxies in the universe local.Las GLCA are small galaxies with an outbreak of highly active stellar formation. Estosobjectos dominate the density of stellar formation in galaxies to travel red intermedios.A spite of the key role that this class of objects is in the evolution of galaxies, susprincipales properties are largely unknown, nor is known very well what is surelación with local populations of galaxies. The HII galaxies are also blue and compact systems that are experiencing a major outbreak of training estelar.Se has suggested that the GLCA could give rise to galaxies in the universe esferoidales close as NGC205 and NGC147. It has also been suggested that the GLCA would result in the bulbs of the first galaxies espirales.Este work consists of three parts. The first is a statistical survey on laspropiedades of galaxies HII more closely match the GLCAs, the second is a study of high spatial resolution about the nature of the GLCA to desplazamientosal red intermediate, and the third part presents a study of the metallicity these objetos.La first part of this study also deals with studying the differences between those galaxies presentanla line auroral emission [OIII] 4363 and those that do not show this feature in its espectro.Las galaxies HII more closely match the GLCA have more common ground withthe subsample not submitting the aforementioned line auroral.También is that the objects without this line are more luminososy have a lower degree of ionization. Its underlying population is also much másimportante and temperatures effective ionizing their piles are probably menores.De the second part of the job is obtained that the GLCA have several regions of stellar formation. This is confirmed with the images obtained direct, which also show a great variety morphological. The GLCAs are kinematically hot systems, in which random movements dominate on rotation to menosen the gas phase. These objects are not immersed in a great record low surface brightness as has been sugerido.También evidence for the existence of stellar generations. One identificacon people responsible for the ionization. The other is the underlying population. Our models indicate that the first episodes of stellar formation occurred ago aproximadamente8 billion years. The poblacionesestelares underlying themes are very similar to those of galaxies HII locale, but posiblementetengan fewer stars relative giants rojas.Por other hand, if the properties of stellar formation of GLCAs are compared with those of the brightest galaxies HII is that lasGLCAs studied are very similar to those HII brightest galaxies in terms of their stellar formation rate per unit area and the relative size of the regions of ionized gas against the overall size of galaxias.En the last chapter presents the a sample survey of 17 galaxies with stellar formation bright but poor in metals, desplazamientosal red z = 0.7. These galaxies are: (1) poorer metals queotras galaxies with strong emission lines in the remote and local universe; (2) comparable with the metallicity much more distant z = 3.0 galaxies of court but less bright and Lyman ( 3) of metallicity comparablea the population of blue compact galaxies extreme, but more luminosas.El overall result suggests that galaxies compact poor in metals more luminosascon outbreaks of stellar formation are becoming weaker.

Author: Casas del Castillo Ricardo.
Year: 2005.
University: GRANADA [More theses of this university] [www.ugr.es].
Place of defense: Facultad de Ciencias.
Place of preparation: Facultad de Ciencias.

Summary: For some time there has been noting the importance of Astrosismología as a tool for studying the internal structure of stars. This has led to a major development of both the theoretical aspects of the linear oscillations (for example, through the development of codes of pulsation) and the observational aspect (including observations from Earth and from satellites). The field theory has experienced a boom in recent times, since until recently the work done imposed approximations to the codes very strong pulse (adiabatic treatment of equations, were not taken into account either interaction with the atmosphere or rotation of the star, and so on.). However, it has been shown that although these treatments allow the study of the fluctuations in some cases (such as the Sun), for many other stars were clearly insufficient. A very interesting of these are the so-called delta Scuti. Its importance lies in presenting multiperiodicidad radial and non - radial, in the absence of magnetic fields and peculiarities of their metallicity. This makes them a special laboratory for the study of stellar pulsations. However, it also presents many complications, such as the presence of convection, or the fact that these stars rotate with moderate or even high speeds. The advent of multicolor photometry as a tool for identifying modes of oscillation has prompted a major boost to both observations and theoretical models. These areas have been developed and refined in parallel, until in recent times has been the need to improve with the first satellite observations (COROT mission, MOST, â |), and the second with the inclusion besides treatment of interactions pulsación-convección and pulsación-rotación, improvements that take into account not adiabaticidad of oscillations and the interaction of these with the stellar atmosphere. The complexity of all these phenomena is such that until now has different numerical codes that focus on one aspect or another, but can not cover all. Even so, it is now possible to carry out a study astrosismológico fairly complete using different algorithms and comparing the results to be obtained. In fact, the Department of Physics Primetime Institute of Astrophysics of Andalusia have codes covering every aspect described, being possible to carry out a comprehensive study of stellar pulsations in a group of stars delta Scuti sufficiently observed by members 's own Institute. The scientific objectives of this thesis fall into the situation described above. It has conducted a survey consistent with the various codes that are available in different aspects of stellar oscillations. We have studied the behavior of non-observable adiabáticos (specifically, the relative variation of the effective temperature, the relative variation of the local gravity, and the so-called "phase lag, ie the phase difference in temperature between the pulsation radio and displacement) along the HR diagram. This involves the use of a code of evolution (CESAM) and a pulse code that includes not adiabaticidad in the equations of oscillation, as well as interaction with the atmosphere. It has already been developed in the Department of Physics Primetime Institute of Astrophysics of Andalusia, and has been sufficiently tested to be able to be used reliably. Moreover, it also has a code of pulsation adiabatic which includes the effects of the rotation until the second order in the rotational speed. Both can be used together to compare 8 resultad 7c8 you. This is important because in the event that the star rotates, the speeds involved, a fact to keep in mind is the degeneration of the ways in rotation: modes with frequencies would be forthcoming "coupled" their frequencies, resulting in significant variations in the value of the same. The study of these data is another novelty of the project. Furthermore, these results were compared with those obtained by the photometric studies of a group of stars. Specifically, it has been used several of those included in the catalog of Rodriguez et al. The comparison between the theoretical and observational results have helped to identify the modes of oscillation, and thus the underlying stellar models. In addition, it has been deepening in the variation of certain magnitudes related to the press along the HR diagram. This is the first work that meets all the elements described in the theoretical analysis of the properties pulsacionales the delta Scuti in a significant portion of the HR diagram. This project represents a support for all the work being done in preparation for the launch of satellite COROT, the French space agency (CNES), scheduled for the year 2006.

Author: BLAY SERRANO PERE.
Year: 2005.
University: VALENCIA [More theses of this university] [www.uv.es].
Place of defense: FACULTAD DE FÍSICA.
Place of preparation: FACULTAD DE FÍSICA.

Author: CABALLERO HERNÁNDEZ JOSE ANTONIO.
Year: 2005.
University: LA LAGUNA [More theses of this university] [www.ull.es].
Place of defense: FACULTAD DE LA LAGUNA.
Place of preparation: UNIVERSIDAD DE LA LAGUNA.

Summary: The brown dwarfs are the bridge between the least massive stars and the giant planets. More than ten years after its discovery .. We tried to make a precise determination of the role of mass in a very young stellar cluster and appropriate for their distance and low extinction, Sigma Orionis, to explore a range of planetary masses until domain. We have studied the stellar populations and subestelar of cúmul9o, including the presence of accretion disks. Moreover, it has investigated the presence of substellar objects as fellow young stars in the solar neighborhood with sensitivity to detect planets, as a complement to search for exoplanets Doppler.

Author: GÁLVEZ ORTIZ M. CRUZ.
Year: 2005.
University: COMPLUTENSE DE MADRID [More theses of this university] [www.ucm.es].
Place of defense: FACULTAD DE CIENCIAS FÍSICAS.
Place of preparation: FACULTAD DE CIENCIAS FÍSICAS.

Summary: There has been a cinematic and spectroscopic study (multilongitud wave) of the chromospheric activity of binary systems assets through various indicators cormosféricos of optical and near-infrared, which has selected a set of systems BY Dra and RS CVn with different levels activity including many with high levels, ie show emissions in most lines cromosféricas of optical and near-infrared. We have studied the characteristics of binary well known and the new binary recently identified by X-ray emissions by radial velocity variations. This would have made a great number of spectroscopic observations over several years, which have enabled one hand cover the different phases or orbital rotation of binary systems and other analyze variability in the longer term. The study multilongitud wave has allowed studying all the indicators of activity simultaneously, thus far, the study of these indicators was limited to the most common (HyK Ca II or Halfa) and usually in a non-simultaneous, which has provided the opportunity to explore the relationship between them and obtain all possible information about the origin of the observed chromospheric emission (beaches, protuberances planned extensive material type bumps in limbo, flares, and microfulguraciones). In addition it has also enabled the determination of accurate radial velocities for which solutions have been obtained orbital and stellar parameters derived from them were also determined speeds of rotation and each star has been estimated ages by the actions of Li I. There will always be a cinematic study of a group of 333 binary stars cromosféricamente active using astrometric data from HIPPARCOS and radial velocities of the literature or certain is this work. It has been studied their belonging to the five most popular youth groups kinematic (Association Local group Ursa Major, supercúmulo of Híades, supercúmulo IC 2391, and group movement Castor) using kinematic criteria and has obtained additional information on age through the presence of Li. It also presents the simultaneous study of the indicators of activity in the optical for 14 binary systems. Have been identified widths equivalent flows and temporal variations. It has been studied in detail five of these systems in addition to the activity that has been secured solution orbital parameters of the system and some stellar derivatives. There has been one hand a detailed study of some systems recently discovered by studying its orbital solution and analyze the activity of the same by identifying widths equivalent flow indicators optical studying further its temporal variations and on the other a study more general level of activity cromoférica of only nine known systems. The comments (with a good coverage Orbital) performed in different eras, it also allows for studying the effect of magnetic activity in the orbital motion of the binary systems (for example, the change of orbital period). It has also been given the isolated nature, binary short period or long period binary, of a sample of 28 stars that good of previous studies of other authors or from studies conducted in recent years by the research group showed changes in the Radial velocity. In addition, for those stars that turned out to be binary short period orbital solution was obtained when possible and also conducted a brief study of its activity indicators cromosféricos. Finally, with a total sample of 46 stars (33 binary systems), of which we have obtained the average values of the flows in the various indicators of activity in the optical and near-infrared, or measured in the course of this work or good spectroscopic observations's prior research group, has undertaken a comprehensive study of the dependence of the activ 8 ity with 355 different parameters stellar through relationships flujo-flujo between indicators and relations flujos-rotación, flujos-período and flujos- Rossby number and has been compared to the behavior of isolated stars. It also has analyzed the peculiarity of binary systems with respect to changing their rotation (due to the timing) and on the sobreactividad and parameters that can make it to be longer or shorter.

Author: CENTENO ELLIOTT REBECA MARIA.
Year: 2006.
University: LA LAGUNA [More theses of this university] [www.ull.es].
Place of defense: AULA TOMAS Y VALIENTE, FACULTAD DE DERECHO.
Place of preparation: INSTITUTO DE ASTROFISICA DE CANARIAS.

Summary: THE STUDY OF THE GENERATION AND PROPAGATION OF WAVES IN THE ATMOSPHERE IS A SOLAR ITEM CANDENTE IN THE INVESTIGATION ASTROPHYSICS PRESENT, AND THAT PROVIDED INFORMATION ON THE STRUCTURE AND THE DYNAMIC OF THE ATMOSFERAS OF THE STARS IN SUN AT THE SAME TIME THAT THEY ARE HELPING UNDERSTAND THE MECHANISMS OF HEATING CROMOSFERICO And CORONAL. DE FACTO, AMONG CANDIDATES FOR PROMISING AS MACHINERY FOR HEATING IS THE WAVES MAGNETOACUSTICAS WITH DISIPACION OF BUMPS AND RECONEXION MAGNETIC. PART ONE OF OUR RESEARCH IS IN THE STUDY FOCUSES ON OSCILACIONES AND PROPAGATION OF WAVES IN DIFFERENT STRUCTURES MAGNETICAS OF THE SUN AIR (STAIN, POROS And FACULAS). THE GOAL IS THE UNIT STUDY OF PROPERTIES OF THE ATMOSPHERE WITH THE FLOW OF MAGNETIC STRUCTURE. THAT HAS BEEN MADE FOR COMMENTS ESPECTROPOLARIMETRICAS IN THE REGION OF 10830 TO ESPECTRAL, CONTAINING AN ONLINE FOTOSFERICA of whether IA 10827 AY A TRIPLETE CROMOSFERICO OF HE IA 10830 A. DEVELOPMENT AND PUTTING A POINT OF SOFISTICADAS TECHNIQUES ALLOW INVESTMENT WE LEARN FROM THE DATA ON TEMPORARY, THE EVOLUTION TIME PHYSICAL CONDITIONS IN THE FOTOSFERA AND CROMOSFERA OF THE STRUCTURES. ANALYZING THE ESPECTROS OF POWERS AND PHASE OF DIFFERENCES WITH AN MODELACION TEORICA SINGLE OF DATA OBSERVACIONALES HAVE CONDUCIDO A VERY INTERESTING RESULT ON THE PROPAGATION OF WAVES AMONG THE FOTOSFERA AND CROMOSFERA. THE FREQUENCY OF ATMOSPHERIC COURT, THE DEVELOPMENT OF BUMPS AND PROPAGATION OF PROPERTIES ARE THE STRUCTURE OF MAGNETIC. BUT SOME FEATURES ARE COMMON TO ALL OF THEM: THE TIME EMPLOYEE OF THE ONE PERTURBACION IN ACHIEVING THE CROMOSFERA FROM FOTOSFERA PRESENTS AN UNIT WITH STRONG THE FREQUENCY, COMING TO BE THE ORDER OF SEVERAL MINUTES IN THE FREQUENCY THAT TRANSPORTAN THE GREATEST PART OF ENERGY . THE OSCILACIONES OBSERVED A ALTURAS CROMOSFERICAS ARISE BASICAMENTE PROPAGATION OF THE SHELF OF DISTURBANCES OBSERVED AT FOTOSFERICO, RATHER THAN GENERARSE FROM THE INTERACTION BETWEEN NON-LINEAR FREQUENCY OF OTHER WAYS, AS CREIA SO FAR. IN THE SECOND PART REALIZAMOS A THEORETICAL STUDY OF THE GENERATION OF THE INTENSITY AND POLARIZACION IN THE LINES ESPECTRALES OF MULTIPLETE OF HE IA 10830 A WHEREOF FORMULAMOS AND TO RESOLVE THE PROBLEM OF TRANSPORTATION RADIATIVO WITHOUT SUPONER ETL REALISTIC MODELS IN THE ATMOSPHERE AND SOLAR USING MODELS ATOMICOS COMPLEX. IS KNOWN AS THE FORMATION OF THIS RASGO ESPECTRAL IS CONTROLLED BY THE IMPACT ON THE CROMOSFERA OF HIGHLY ENERGETICA RADIATION FROM THE CROWN SOLAR. THE IMPLEMENTATION OF A CODE OF GENERAL USE IN THE FORMALISMO MALI (MULTI-LEVEL ACCELERATED LAMBDA-ITERATION) WE HAS ALLOWED SINTETIZAR THE MULTIPLETE OF SIN SUPONER ETL I HE, AND STUDY FOR THE FIRST TIME THE RESPONSE OF PROFILING STOKES TO THIS EMERGING RADIATION IONIZANTE, BOTH ON THE DISK LIMBO AS OUT OF SOLAR.

Author: Gutierrez Soto Juan.
Year: 2006.
University: VALENCIA [More theses of this university] [www.uv.es].
Place of defense: Facultad de Farmacia.
Place of preparation: Facultad de Matemáticas.

Summary: The general objective of the present work is to contribute to the knowledge of the physics of Be Stars. In particular, we are interested in studying and characterizing their pulsational properties. A very suitable tool to reach this goal is the study and analysis of photometric time series with the maximum time baseline, density and photometric accuracy. The space mission COROT scheduled to be launched in December 2006, will provide ultra high precision, relative stellar photometry for very long continuous observing runs. Up to ten stars will be observed in the seismology fields with a photometric accuracy of a few 10-4 and color information. The observations of Be stars with COROT will provide photometric time series with unprecedented quality. Their analysis will allow us to qualitatively improve our knowledge and understanding of the pulsational characteristics of Be stars. In consequence, we have started a research project aimed at observing Be stars both in the seismology and exoplanet fields of COROT. In this thesis we present the firs step of this project, which is the preparation and study of the sample of Be stars that will be observed by COROT. We have performed photometric analysis of all Be stars located in the seismology fields (Chapt. 2). Special emphasis has been given to two stars (NW Ser and V1446 Aql) in wich we have detected multiperiodic variability and which we have modeled in terms of stellar pulsations (Chap. 3). We have also performed an in-dept spectroscopic study of NW Ser and modeled the non-radial pulsations taking into account the rotational effects (Chap. 4) A technique to search for faint Be stars based on CCD photometry has been developed and is presented in Chap. 5. In the same chapter, we present a list of faint Be stars located in the exoplanet fields of COROT detected with this technique and which we propose as targets for COROT. In addition, we have proved that our period-analysis techniques are suitable to detect miltiperiodicity in large temporal baseline data (Chapt. 6). In particular, we have detected non.-radial pulsations in some Be stars in the low-metallicity galaxy SMC.

Author: DOMÍNGUEZ HERRERA MARÍA DEL CARMEN.
Year: 2006.
University: LA LAGUNA [More theses of this university] [www.ull.es].
Place of defense: FACULTAD DE EDUCACIÓN. MÓDULO A..
Place of preparation: FACULTAD DE EDUCACIÓN.

Summary: The thesis develops within the area Didactics of Experimental Sciences. Broadly, the research theme addresses three major issues: The language of science, the teaching of scientific concepts and the development of teaching resources for the teaching-learning. This work is positioned mainly in the first, concretándose analysis of the concepts inherent in the Solar System that appear in textbooks of basic education.

Author: Andrade Baliño Manuel.
Year: 2006.
University: SANTIAGO DE COMPOSTELA [More theses of this university] [www.usc.es].
Place of defense: Facultad de Matemáticas.
Place of preparation: Facultad de Matemáticas.

Summary: We have studied the problem of Gyldén-Mescerskij, namely, the problem of two bodies with variable mass when, overlapping with the temporary loss of mass, are considered different disturbances. In particular, he examines the phenomenon of increased mass loss by gravitational effect, the so-called `effect periastro ', revealing that could be the cause of relatively high values of eccentricity in some binary systems. In addition, deals with the case in which one of the components of the system presents ellipsoid shape considering relativistic effects in some approximation post-newtoniana. To attack the mathematical these scenarios disturbed analytical techniques are used both as a numeric. Among the first highlights a canonical perturbation method based on changes Lie, presented here for the first time, reflecting a widespread aN parameters of the classic method Lie-Deprit. The stability of some real hierarchical triple systems is examined over time using different criteria. For the display of the regions of stability is defined maps ad hoc according to the semi-major axis and eccentricity of the orbit outside. Finally, it provides a model of winds laden with mass based on a distribution function of mass defined on the basis of three factors shape of the stellar wind. This model is used for the integration of some hypothetical orbital configuration in a binary system Wolf-Rayet.

Author: Carretero Herráez Conrado.
Year: 2006.
University: LA LAGUNA [More theses of this university] [www.ull.es].
Place of defense: Facultad de Física y Matemáticas.
Place of preparation: Instituto de Astrofísica de Canarias.

Summary: In this thesis we have made a detailed study of stellar populations in elliptical galaxies in clusters of different mass. Our results suggest that the time scales of formation of stars in these galaxies are dependent on the environment in which they are: the stars of massive clusters of galaxies are formed faster than those in less dense environments. In all cases, there is a limit to these times of 1000 million years.

Author: Oreiro Rey Raquel.
Year: 2006.
University: LA LAGUNA [More theses of this university] [www.ull.es].
Place of defense: Facultad de Física Universidad La Laguna.
Place of preparation: Instituto de Astrofísica de Canarias.

Summary: This thesis focuses on the study of the stars subenanas Hot Type B (sdBs). Such objects show spectral properties similar to those of B-type stars in the Main Stream, and are characterized by low luminosity, which falls below that in a sequence diagram Hertzsprung-Russell. Currently sdBs are under review from different research areas. In particular, the recent discovery of stellar oscillations in part helps her study from a seismological point of view. This work is intended to deepen the implementation of the seismic event of the sdBs. On the one hand, it has been used profitably observation method for the detection of new sdBs pulsating, especially those with shorter periods. As a result, have found four new sdBs pulsating, one of which has resulted in the show beats ranges theoretically attributed to acoustic oscillation modes and gravity, becoming one of the most interesting objects in its class. Also, campaigns have been exhaustive on some sdBs oscillating, in order to fully characterize its spectral fluctuations. Moreover, from a theoretical point of view, it has generated a network of models covering the range of structural parameters typical sdBs, these being models complete structure, unlike the envelope models used for analysis by other similar groups. It has come to the calculation of the properties of oscillatory previous models, conducting a study on the results obtained. Finally, it establishes a procedure for frequency compared with those of observational network models based on the optimization of observational information, which can be compared to the properties derived from the theoretical study. This technique is applied to the three sdBs pulsating observed in greater detail during the argument, deriving important information on ways observational and physical properties of objects.

Author: Olivares Pulido Germán.
Year: 2006.
University: AUTÓNOMA DE BARCELONA [More theses of this university] [www.uab.es].
Place of defense: Facultad de Ciencias.
Place of preparation: Facultad de Física.

Summary: In 1998, measurements of the luminosity distance of a handful of supernovae Type Ia hinted at an accelerated expansion of the present Universe. Since then, several observational data sets including CMB and LSS lent further support to the idea of a spatially flat universe dominated by a cosmological constant, Lambda, with 70% of the total energy density and Cold Dark Matter energy density 3% of it. Although the Lambda CDM model fits reasonably well all observational data it faces two serious theoretical problems. In the first place, a fine-tuning problem. The observed cosmological constant is about 121 times smaller than the value predicted by quantum field theory. This is why scalar fields were proposed as an alternative to the cosmological constant; they naturally arises in particle physics including string theory. Up to now, a wide variety of scalar fields dark energy models have been suggested. These include quintessence, phantoms, k-essence, tachyon, ghost condensates and dilatonic dark energy amongst many others. Quintessence scalar fields present energy scales compatible with the energy scale of particle physics. This may help alleviate the severe fine-tuning problem of the cosmological constant. In the second place, it appears rather unnatural that the densities of two components, cold dark matter and dark energy, that evolve so differently with expansion happen to be of the same order precisely today. This is the coincidence problem. In order to solve, or alleviate it, models featuring an interaction between dark energy and matter were advanced proposed.In Chapter 2 we studied the Interacting Quintessence Model of Chimento et al. The interaction is proposed from a phenomenological viewpoint. The dark energy decays into cold dark matter in such a way that their ratio remains constant during the late epoch of accelerated expansion, thus substantially alleviating the coincidence problem. This kind of solutions, known as scaling solutions prove useful to obtain an acceptable accelerated expansion as long as dark energy and cold dark matter are strongly coupled. Because of the interaction there is less cold dark matter in the past. Therefore, the luminosity distance augments. The higher the redshift, the larger the difference between the amount of cold dark matter in non-interacting models and interacting models. At low redshifts, however, they are very similar. Observational SN Ia data sets do not help discriminate interacting from non-interacting models because the amount of cold dark matter and dark energy in both models at low redshifts are barely different. We showed that the proposed interaction naturally leads the Universe from a radiation dominated era, through a matter dominated era, to the current accelerated expansion phase driven by the negative pressure of the dark energy. Unlike others models, we do not need to adjust the interaction parameter to avoid a baryon dominated epoch. Moreover, the corresponding potential of the dark energy is such that for a wide range of initial conditions the solutions enters the scaling regime followed by an accelerated expansion of the Universe once the potential becomes shallow. In fact, the potential has the same asymptotic behavior as the one suggested by Sahni and Wang. We note that the mass of the scalar field depends on the background energy density. Thus, while it can remain relatively light at the scale of solar system it can become much heavier at cosmological scales. This behavior is typical of Chameleon fields. If the IQM were actually of Chameleon type, it could evade violation of the equivalence principle at scales of the solar system. On the other hand, as studied in Chapter 3 the cold dark matter perturbations evolve more slowly than in non-interacting models, i.e., at large scales they do not longer vary as a(t). Thus, the effective gravitational force is reduced and the mean free--fall time increases while the density perturbations grow slower (or get even erased), compared 8 with no 1047 n--interacting models. Scalar fields coupled to matter modify gravity inducing an extra attractive force. A repulsive effect could be obtained by the exchange of vector bosons. It was first suggested by Amendola that phantom scalar fields with non-standard kinetic term coupled to matter would give rise to a long-ranged repulsive force. In the model of Chimento et al, the decrease of the gravitational coupling is due to its specific interaction for the dark matter--dark energy interaction. We note that it could violate the equivalence principle as suggested by Amendola. The interaction renders the gravitational potential shallower in the matter dominated epoch. Therefore it modifies the acoustic peaks of the CMB. More precisely, as there is no interaction with the baryons, the relative heights of the acoustic peaks diminish. Thus, in interacting models the CMB is very sensitive to the dark energy, for the interaction modifies the scaling with redshift of the cold dark matter. Consequently, CMB data sets are very useful to constrain the interaction parameter. In Chapter 5 we saw that CMB data hardly constrain the interaction. The effect of the interaction on the evolution of the gravitational potential and, consequently, on the CMB acoustic peaks cannot be balanced by any other physical mechanism. Therefore, the predictions of the IQM model can deviate from predictions of the Lambda CDM model up to a certain value. Beyond that, the data strongly reject the model.The matter power spectrum also feels the interaction. As the interaction increases, the potentials become shallower and the slope of the matter power spectrum, at scales larger than the matter-radiation equivalence, drops. Further, the less cold dark matter in the past, the smaller the scale at the redshift of matter-radiation equality. As a consequence, the peak of the matter power spectrum shifts. Although warm dark matter can also lead to a smaller amplitude of the matter power spectrum at radiation scales, the shift of the peak is a distinguishing feature of the interaction. Only interacting models show this property irrespective of the interaction between cold dark matter and dark energy. The statistical analyses with LSS data set are in good agreement with the results obtained with CMB data set, though the former do not provide much more information than the last.In non-interacting models, an ISW effect appears whenever the background energy density evolves differently from cold dark matter. As soon as the amounts of dark energy and cold dark matter are of the same order the gravitational potentials evolve giving rise to new perturbations on the radiation distribution. In interacting models, an ISW effect can arise also in the matter dominated epoch, as cold dark matter perturbations no longer evolve as in non-interacting models. Therefore, the interaction increases the early and late ISW effects. Cross-correlations of the CMB spectrum with galaxies catalogs are pointed out to be very useful to constrain the equation of state parameter of dark energy. Therefore, the ISW effect may prove a useful tool to constrain the interaction parameter but at present it does not have enough statistical power to do so. To summarize, interacting models substantially alleviate the coincidence problem and fit well the observational data. The possible violation of the equivalence principle at large scales could give a hint of new physics, thus setting up a limit for general relativity.