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Context. At about 1000 days after the launch of Gaia we present the first Gaia data release, Gaia DR1, consisting of astrometry and photometry for over 1 billion sources brighter than magnitude 20.7. Aims. A summary of Gaia DR1 is presented along with illustrations of the scientific quality of the data, followed by a discussion on the limitations due to the preliminary nature of this release. Methods. The raw data collected by Gaia during the first 14 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into an astrometric and photometric catalogue. Results. Gaia DR1 consists of three components: a primary astrometric data set which contains the positions, parallaxes, and mean proper motions for about 2 million of the brightest stars in common with the Hipparcos and Tycho-2 catalogues - a realisation of the Tycho-Gaia Astrometric Solution (TGAS) - and a secondary astrometric data set containing the positions for an additional 1.1 billion sources. The second component is the photometric data set, consisting of mean G-band magnitudes for all sources. The G-band light curves and the characteristics of ∼ 3000 Cepheid and RR-Lyrae stars, observed at high cadence around the south ecliptic pole, form the third component. For the primary astrometric data set the typical uncertainty is about 0.3 mas for the positions and parallaxes, and about 1 mas yr−1for the proper motions. To the parallax uncertainties a systematic component of ∼ 0.3 mas should be added. For the subset of ∼ 94 000 Hipparcos stars in the primary data set the proper motions are much more precise, at about 0.06 mas yr−1 . For the secondary astrometric data set the typical uncertainty of the positions is ∼ 10 mas. The median uncertainties on the mean G-band magnitudes range from the mmag level to ∼ 0.03 mag over the magnitude range 5 to 20.7. Conclusions. Gaia DR1 is an important milestone ahead of the next Gaia data release, which will feature 5-parameter astrometry for all sources. Extensive validation shows that Gaia DR1 represents a major advance in the mapping of the heavens and the availability of basic stellar data that underpin observational astrophysics. Nevertheless the very preliminary nature of this first Gaia data release does lead to a number of important limitations to the data quality which should be carefully considered before drawing conclusions from the data.

The HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhood has been constructed using astrometric data from Hipparcos satellite as well as photometric and radial velocity data. The LM method \cite{luri95,luri96} allows the use of proper motion and radial velocity data in addition to the trigonometric parallaxes to obtain luminosity calibrations and improved distances estimates. Six types of Bp - Ap stars have been examined: He-rich, He-weak, HgMn, Si, Si+ and SrCrEu. Most Bp - Ap stars lie on the main sequence occupying the whole width of it (about 2 mag), just like normal stars in the same range of spectral types. Their kinematic behaviour is typical of thin disk stars younger than about 1 Gyr. A few stars found to be high above the galactic plane or to have a high velocity are briefly discussed. Based on data from the ESA Hipparcos astrometry satellite and photometric data collected in the Geneva system at ESO, La Silla (Chile) and at Jungfraujoch and Gornergrat Observatories (Switzerland). Tables 3 and 4 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

The absolute magnitude of barium stars has been obtained from kinematical data using a new algorithm based on the maximum-likelihood principle. The method allows to separate a sample into groups characterized by different mean absolute magnitudes, kinematics and z-scale heights. It also takes into account, simultaneously, the censorship in the sample and the errors on the observables. The method has been applied to a sample of 318 barium stars. Four groups have been detected. Three of them show a kinematical behaviour corresponding to disk population stars. The fourth group contains stars with halo kinematics. The luminosities of the disk population groups spread a large range. The intrinsically brightest one (M_v_=-1.5mag, σ_M_=0.5mag) seems to be an inhomogeneous group containing barium binaries as well as AGB single stars. The most numerous group (about 150 stars) has a mean absolute magnitude corresponding to stars in the red giant branch (M_v_=0.9mag, σ_M_=0.8mag). The third group contains barium dwarfs, the obtained mean absolute magnitude is characteristic of stars on the main sequence or on the subgiant branch (M_v_=3.3mag, σ_M_=0.5mag). The obtained mean luminosities as well as the kinematical results are compatible with an evolutionary link between barium dwarfs and classical barium giants. The highly luminous group is not linked with these last two groups. More high-resolution spectroscopic data will be necessary in order to better discriminate between barium and non-barium stars.

A new maximum likelihood method, using apparent magnitudes, proper motions and radial velocities, has been applied to a sample of 90 Mira stars extracted from the HIPPARCOS Input Catalogue (INCA) to determine absolute magnitudes and kinematics. Using this new method three different groups of Mira stars have been identified in the sample, with different luminosities, kinematics and scale height. Two of them are well determined and are identified respectively with the old disk population and the extended thick disk-halo population. The third one is too small and peculiar and its identification has to be left for further studies. Using these results the stars of the sample are classified into the groups and their distances are estimated. These distances are compared with independent determinations obtained from K-band and near-infrared narrow band photometry.

We present new optical and infrared photometric observations and high resolution H α spectra of the periodic radio star LSI+61◦303. The optical photometric data set covers the time interval 1985-1993 and amounts to about a hundred nights. A period of ∼26 days is found in the V band. The infrared data also present evidence for a similar periodicity, but with higher amplitude of variation ((0.m 2). The spectroscopic observations include 16 intermediate and high dispersion spectra of LSI+61◦303 collected between January 1989 and February 1993. The H α emission line profile and its variations are analyzed. Several emission line parameters -- among them the H α EW and the width of the H α red hump -- change strongly at or close to radio maximum, and may exhibit periodic variability. We also observe a significant change in the peak separation. The H α profile of LSI+61◦303 does not seem peculiar for a Be star. However, several of the observed variations of the H α profile can probably be associated with the presence of the compact, secondary star.

An accurate determination of the Malmquist bias is obtained using an analytical approach which takes into account a more realistic space distribution than that in the traditional Malmquist approximation. The bias is found to be a function of several sample parameters in addition to the well-known dependence on the dispersion of the absolute magnitude.

In an analysis of proper motions of O and B stars contained the Input Catalogue for Hipparcos, we have found a clear deviation from the expected pattern of systematic motions which can be readily identified with the associations Cygnus OB1 and Cygnus OB9, located near de the edge of the Cygnus Superbubble. Teha anomalous motions are directed outwards from the center of the Superbubble, which is coincident with tha association Cygnus OB2. This seems to support the hypothesis of a strong stellar and supernova activity in Cygnus 0B2 giving rise to the Superbubble and, by means of gravitational instabilities in its boundaries, to Cygnus 0B1 and Cygnus OB9. New uvby-beta aperture photometry of selected O and B stars in the area of Cygnus OB1 and Cygnus OB9 is also presented and analyzed in this paper.

A statistical development is presented to use the positional information in photometric planes - the information contained in the position of a star with respect to a calibration line. This development is applied in the case of color-color planes, defining what we call the proximity parameter, which is used for luminosity classification purposes and for an improved use of calibrations.

As indicated by Grenon (1989), the data of the present series of reports on the UBVRI photometry of late-type stars in the Hipparcos Input Catalog are to be employed in computations of Hipparcos observing time, as well as in evaluating the observability of faint stars by the satellite. Attention is here given to late type stars in the V = 8-12 range, including distant red giants in the Galactic plane (Hipparcos proposal 189), as well as high proper motion stars included in the G, LTT, LP, and MCC catalogs.

UBVRI photoelectric photometry is presented for 269 late spectral type, high proper motion stars belonging to the 'Lowell Proper Motion Survey' and included in the present version of the Hipparcos Input Catalogue. The observations and data reduction are described. The external errors obtained by comparison of the results with those obtained in other studies are presented.

Hydrodynamical equations act as a link between the local observed magnitudes of galactic motion and the general ones accounting for the behaviour of the Galaxy as a whole. Constraints are set usually in order to use them even in the lower order hierarchy. The authors present in this paper the complete expressions up to their fourth order. These equations will be used in the next future in their general form taking into account both the expected increase of kinematic data that the astrometric mission Hipparcos will provide, and some recent results indicating the possibility to obtain estimates for the momenta gradients.

Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.

Context. We present the second Gaiadata release, Gaia DR2, consisting of astrometry, photometry, radial velocities, and information on astrophysical parameters and variability, for sources brighter than magnitude 21. In addition epoch astrometry and photometry are provided for a modest sample of minor planets in the solar system. Aims. A summary of the contents of Gaia DR2 is presented, accompanied by a discussion on the differences with respect to Gaia DR1 and an overview of the main limitations which are still present in the survey. Recommendations are made on the responsible use of Gaia DR2 results. Methods. The raw data collected with the Gaia instruments during the first 22 months of the mission have been processed by the Gaia Data Processing and Analysis Consortium (DPAC) and turned into this second data release, which represents a major advance with respect to Gaia DR1 in terms of completeness, performance, and richness of the data products. Results. Gaia DR2 contains celestial positions and the apparent brightness in G for approximately 1.7 billion sources. For 1.3 billion of those sources, parallaxes and proper motions are in addition available. The sample of sources for which variability information is provided is expanded to 0.5 million stars. This data release contains four new elements: broad-band colour information in the form of the apparent brightness in the GBP (330-680 nm) and GRP (630-1050 nm) bands is available for 1.4 billion sources; median radial velocities for some 7 million sources are presented; for between 77 and 161 million sources estimates are provided of the stellar effective temperature, extinction, reddening, and radius and luminosity; and for a pre-selected list of 14 000 minor planets in the solar system epoch astrometry and photometry are presented. Finally, Gaia DR2 also represents a new materialisation of the celestial reference frame in the optical, the Gaia-CRF2, which is the first optical reference frame based solely on extragalactic sources. There are notable changes in the photometric system and the catalogue source list with respect to Gaia DR1, and we stress the need to consider the two data releases as independent. Conclusions. Gaia DR2 represents a major achievement for the Gaia mission, delivering on the long standing promise to provide parallaxes and proper motions for over 1 billion stars, and representing a first step in the availability of complementary radial velocity and source astrophysical information for a sample of stars in the Gaia survey which covers a very substantial fraction of the volume of our galaxy.

Context. The Gaia spacecraft of the European Space Agency (ESA) has been securing observations of Solar System Objects since the beginning of its operations. The Data Release 2 (DR2) contains the observations of a selected sample of 14,099 Solar System Objects, SSOs for brevity. These asteroids were already identified and numbered by the Minor Planet Center repository. Positions are provided for each Gaia observation, at CCD level. As additional information, complementary to astrometry, the apparent brightness of SSOs in the unfiltered G band is also provided for selected observations. Aims. We explain the processing of SSO data, and the criteria used to select the sample published in the Gaia DR2. We then explore the data set to assess its quality. Methods. To exploit the main data product for the Solar System in Gaia DR2, namely epoch astrometry of asteroids, it is necessary to take into account the unusual properties of the uncertainty, as the position information is nearly one-dimensional. Once this aspect is appropriately handled, an orbit fit can be obtained, with post-fit residuals that are overall consistent with the a-priori error model used to define individual values of the astrometric uncertainty. The role of both random and systematic errors is described. The distribution of residuals allows us to identify possible contaminants in the data set (such as stars). Photometry in the G band is compared to computed values from reference asteroid shapes and to the flux registered, at the corresponding epochs, by the red and blue photometers (RP and BP). Results. The overall astrometric performance is close to the expectations, with an optimal range of brightness G 12-17. In that range the typical transit-level accuracy is well below 1 milliarcsec (mas). For fainter asteroids, the growing photon noise deteriorates the performance. Asteroids brighter than G = 12 are aff ected by a lower performance of the processing of their signals. The dramatic improvement brought by Gaia DR2 astrometry of SSOs is demonstrated by comparisons to the archive data, and by preliminary tests on the detection of subtle non-gravitational effects.

A second set of UBVRI photometry results for nearby stars of Gliese's (1969) catalog and its supplements, including in this case some multiple systems, are presented. Most of the observations were carried out between July 1984 and December 1985 at Calar Alto with the 1.23-m Centro Astronomico Hispano-Aleman telescope and the 1.52-m Observatorio Astronomico Nacional telescope. The number of observations of program and standard stars for the six runs and the final results for 60 stars are presented.

In order to complete the photometric data of the Gliese (1969) 'Catalog of Nearby Stars', and in addition use these data for the Hipparcos space astrometry mission, program stars have been selected from the catalog and its supplements on the basis of their having an incomplete set of UBVRI photometric data of magnitude lower than 13. The program developed rejects determinations of any magnitude or color index having a residual greater than 2(sigma-prime), where sigma-prime is the standard deviation for the determinations of unit weight.

UBVRI data are presented for a set of 229 late-type stars, most of them being high proper motion stars. All these data are part of the Input Catalog planned observations for the Hipparcos mission.

Context. The second release of Gaia data (Gaia DR2) contains the astrometric parameters for more than half a million quasars which define akinematically non-rotating reference frame in the optical domain. A subset of them have accurate VLBI positions which allow the axes of thereference frame to be aligned with the ICRF radio frame. Aims. We aim to describe the astrometric and photometric properties of the quasars selected to represent Gaia-CRF2, the celestial reference frame of Gaia DR2, and to compare the optical and radio positions for sources with accurate VLBI positions. Methods. Descriptive statistics are used to characterise the overall properties of the quasar sample. Residual rotation and orientation errors and large-scale systematics are quantified by means of expansions in vector spherical harmonics. Positional differences are calculated relative to a prototype version of the forthcoming ICRF3. Results. Gaia-CRF2 is materialised by the positions of a sample of 556 869 sources in Gaia DR2, obtained from a positional cross-match with the ICRF3-prototype and AllWISE AGN catalogues. The sample constitutes a clean, dense, and homogeneous set of extragalactic point sources in the magnitude range G ' 16 to 21 mag with accurately known optical positions. The median positional uncertainty is 0.12 mas for G < 18 mag and 0.5 mas at G = 20 mag. Large-scale systematics are estimated to be in the range 20 to 30 μas. The accuracy claims are supported by the parallaxes and proper motions of the quasars in Gaia DR2. The optical positions for a subset of 2820 sources in common with the ICRF3-prototype show very good overall agreement with the radio positions, but several tens of sources have significantly discrepant positions. Conclusions. Based on less than 40% of the data expected from the nominal Gaia mission, Gaia-CRF2 is the first realisation of a non-rotating global optical reference frame meeting the ICRS prescriptions, i.e. built only on extragalactic sources. In accuracy it matches the current radio frame realised in the ICRF but with a much higher density of sources in all parts of the sky except along the Galactic equator.

We present Stroemgren uvby and Hbeta_ photometry for a set of 575 northern main sequence A type stars, most of them belonging to the Hipparcos Input Catalogue, with V from 5mag to 10mag and with known radial velocities. These observations enlarge the catalogue we began to compile some years ago to more than 1500 stars. Our catalogue includes kinematic and astrophysical data for each star. Our future goal is to perform an accurate analysis of the kinematical behaviour of these stars in the solar neighbourhood.

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2016, Tutor: Jordi Torra, We have studied the annual evolution of Night Sky Brightness (NSB) in the urban area of Barcelona using a Sky Quality Meter photometer pointing to the zenith. Annual, monthly and daily moonlight effects have been considered and analysed and we have searched for changes in brightness at zenith due to singular events

Aquesta tesi doctoral se centra en l'estudi de la contaminació lumínica tant en zones urbanes com en zones protegides de Catalunya. S'entén per contaminació lumínica qualsevol efecte advers produït per la llum artificial com pot ser l'emissió de llum cap al cel, l'enlluernament o també l'ús d'enllumenat en indrets, horaris o amb tipus de llum inadequats. Si bé la contaminació lumínica sempre s'ha relacionat amb l'observació del cel i amb l'astronomia, no és només en aquest àmbit que es detecten els seus efectes sinó que es troben cada cop més habitualment estudis que mostren els seus efectes en el medi ambient, en la salut humana o com no en el consum energètic d'un territori. Una de les formes d'avaluar i caracteritzar la contaminació lumínica és la mesura de la brillantor de fons de cel, que es pot realitzar amb diverses tècniques i dispositius, des dels sistemes clàssics basats amb telescopi i càmeres CCD fins als dispositius dissenyats específicament com els Sky Quality Meters o els dispositius ull de peix. La gran diversitat d'aparells existents fa que un dels focus d'aquesta tesi siguin els treballs de comparació i calibració d'instruments que permeten millorar la seva precisió i posar-los en disposició per la constitució de xarxes de mesura contínua. La mesura de la brillantor de fons de cel és pot enfocar de dos punts de vista, per una banda les mesures extensives al llarg d'un territori i per l'altra banda les mesures contínues en emplaçaments permanents en mode de xarxa. En aquest treball s'han utilitzat ambdós punts de vista amb els objectius d'elaborar el mapa de contaminació lumínica de Catalunya i avaluar els canvis temporals de la brillantor de fons de cel. Els mapes de contaminació lumínica són una eina per conèixer l'estat del cel en un territori. Per tal de construir-los ha calgut la realització de mesures recorrent el territori a estudiar, així com definir mètodes de filtratge i selecció de les dades que han conduit a una metodologia completa per l'elaboració d'aquests mapes a partir de mesures de fons de cel realitzades amb dispositius Sky Quality Meter. L'anàlisi de les zones estudiades ha permès constatar l'alta qualitat del cel de la zona Starlight de la serra del Montsec amb els valors característics del cel natural. Així també s'ha pogut avaluar els efectes que genera una ciutat com Lleida que incideixen en la brillantor de cel en el zenit fins més enllà de 20 quilòmetres de la localitat. Un element clau d’aquest treball ha estat el disseny i posada en marxa de la Xarxa de Contaminació Lumínica de Catalunya (XCLCat) amb aparells permanents que permeten de forma continua analitzar la brillantor del fons de cel. Amb les dades recollides durant més d’un any des de la posada en marxa de les primeres estacions s’ha pogut avaluar com en les zones urbanes la brillantor del cel és tan elevada que en alguns moments de l’any ni tan sols es detecta el cicle lunar. Per altra banda en zones protegides amb cels excel.lents s’ha pogut avaluar l’efecte de la Via Làctia en travessar el zenit incrementant la brillantor del fons de cel en gairebé mitja magnitud. Aquestes sèries temporals obren la porta a estudis combinats amb paràmetres ambientals com poden ser els núvols; hem determinat per primera vegada de forma quantitativa com la seva presència en espais protegits fa que el cel sigui encara més fosc contràriament al que succeeix en zones urbanes on els núvols poden fer augmentar la brillantor de fons de cel en fins a dues magnituds. La obtenció contínua de dades permetrà completar aquests estudis amb altres variables ambientals i permetrà avaluar canvis en la qualitat de cel amb el pas dels anys., This thesis is focused on the study of Light Pollution (LP) in urban and protected areas of Catalonia. Light pollution is any effect generated by artificial lighting. Normally Light Pollution is associated with astronomy, but there are many other effects in natural environment, health or power consumption. The evaluation of LP can be done measuring the night sky brightness (NSB) using for example telescopes and cameras or using stand-alone devices for this purpose. One of the topics of this work is the intercomparison and calibration of these devices to improve their precision and use them to establish a LP measurement network. We have measured NSB with two approaches: extensive measurements covering a large area as well as permanent stations to analyze the evolution of the NSB. The extensive measurements allow us to generate maps of light pollution of an area. To do that we have defined routes and a good strategy of filtering and data selection. With this method we can create light pollution maps from Sky Quality Meters measurements. With these maps we can evaluate different areas and we can confirm the good quality of the Starlight protected area of Montsec with NSB compatible with a natural area. In the other hand we can evaluate the effects of the near city of Lleida that affects zenithal measurements up to 20 km far from the city. We have created the Catalan Light Pollution Network with all the specifications and methods to do a permanent monitoring of the NSB. After one year of operation we can evaluate how the lunar cycle is almost not detectable in some periods in urban areas or how the Milky Way could affect the measurements in really dark sites with an increase of brightness up to 0.5 magnitudes. Monitoring measurements in combination with environmental data allow us to study the effects of clouds in NSB. We have determined for the first time ever how the clouds could generate a reduction of measured NSB in pristine areas meanwhile in urban areas the same kind of clouds increases the NSB up to 2 magnitudes. In the near future with more data available any other environmental parameters could be analyzed and long term evolution of light pollution could be studied.

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Curs: 2016, Tutor: Jordi Torra, The cross-match (XM) is a sophisticated task that links all the Gaia observations with entries in the source catalogue. The main objective of this project is to perform a comparative analysis of several clustering algorithms that will be part of the XM of the Gaia detections to sources. The clustering results generated by each method will be compared against the true XM resolution provided by a simulator. Finally, a decision will be made based on the results of this comparative analysis regarding the selection of the clustering algorithm which best fits the XM requirements to be used in the Gaia data treatment

[spa] Gaia es la misión espacial astrométrica más ambiciosa de la Agencia Espacial Europea (ESA). El satélite fue lanzado el 19 de Diciembre de 2013 y su objetivo principal es la determinación, con una resolución y precisión sin precedentes, de las posiciones, distancias y velocidades de más de mil millones de estrellas de nuestra galaxia. Esta Tesis se centra en el desarrollo del sistema de procesado IDU, "Intermediate Data Updating". IDU es una de las etapas de calibración instrumental y reducción de datos astrométricos más exigente del sistema de procesado del satélite Gaia. Sin este sistema, Gaia no podría alcanzar el nivel de precisión que se quiere obtener y su presencia es fundamental para lograr la convergencia óptima del sistema iterativo de procesado de datos en el que se basa la reducción de datos de Gaia. El procesado de los datos de Gaia es un gran reto tecnológico. En particular, el gran volumen de datos a procesar y el elevado número de procesos involucrados ha implicado el diseño de un sistema de distribución y procesado de datos muy complejo. Este procesado se basa en un sistema iterativo entre varios procesos en el que se añaden de manera continuada los nuevos datos recibidos del satélite. De entre estos procesos, esta tesis se centra en el diseño e implementación de IDU, donde se vuelven a procesar todos los datos brutos usando las calibraciones más recientes obtenidas del resto de procesos. El diseño e implementación de IDU ha supuesto una gran variedad de retos; incluyendo los problemas puramente científicos pero también las dificultades técnicas que aparecen en el procesado del gran volumen de datos de Gaia y la gestión de todas las tareas de desarrollo, test y coordinación de los equipos que contribuyen a este sistema. IDU se ejecuta en el supercomputador Marenostrum, gestionado por el "Barcelona Supercomputing Center" (BSC). Finalmente, esta tesis incluye los resultados de la primera ejecución operacional de IDU la cual ha servido para demostrar que el sistema desarrollado esta listo para afrontar el exigente reto de procesar los datos reales de Gaia durante los próximos años de misión., [eng] Gaia is an extremely ambitious astrometric space mission adopted within the scientific programme of the European Space Agency (ESA) in October 2000. It aims to measure with very high accuracy the positions, motions and parallaxes of a large number of stars and galactic objects, including also for almost all the objects information about their brightness, colour, radial velocity, orbits and astrophysical parameters. Gaia requires a demanding data processing system on both data volume and processing power. The treatment of the Gaia data has been designed as an iterative process between several systems each one solving different aspects of the data reduction system. In this thesis we have addressed the design and implementation of the Intermediate Data Updating (IDU) system. IDU is the instrument calibration and astrometric data processing system more demanding in data volume and processing power of the data processing system of the Gaia satellite data. Without this system, Gaia would not be able to provide the envisaged accuracies and its presence is fundamental to get the optimum convergence of the iterative process on which all the data processing of the spacecraft is based. The design and implementation of an efficient IDU system is not a simple task and a good knowledge of the Gaia mission is fundamental. The design and implementation of IDU is not only referring to the actual design and coding of the system but also to the management and scheduling of all the related development tasks, system tests and in addition the coordination of the teams contributing to this system. The developed system is very flexible and modular so it can be easily adapted and extended to cope with the changes on the operational processing requirements. In addition, the design and implementation of IDU presents a variety of interesting challenges; covering not only the purely scientific problems that appear in any data reduction but also the technical issues for the processing of the huge amount of data that Gaia is providing. The design has also been driven by the characteristics and restrictions of the execution environment and resources -- Marenostrum supercomputer hosted by the Barcelona Supercomputing Center (BSC) (Spain). Furthermore, we have developed several tools to make the handling of the data easier; including tailored data access routines, efficient data formats and an autonomous application in charge of handling and checking the correctness of all the input data entering and produced by IDU. Finally, we have been able to test and demonstrate how all the work done in the design and implementation of IDU is more than capable of dealing with the real Gaia data processing. We have basically executed two of the IDU tasks over the first ten months of routine operational Gaia data. This execution has been the very first cyclic data processing level run over real data so far. Executing IDU at Marenostrum over that amount of data for the first time has been a challenging task and from the results obtained we are confident that the system, we have designed and that constitutes the bulk of this thesis, is ready to cope with the Gaia data according to the requirements sets. Furthermore, the presented design provides a solid IDU system foundation for the challenging task of processing the Gaia data during the forthcoming years.

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2015, Tutor: Jordi Torra, The main goal is to develop efficient tools to help validating the data received daily from the Gaia satellite. In order to do so, we study the main data processes and their outputs and build three different tools called ExtendedStats, FlIdtValidation and AutoAlarms.

Treballs Finals de Grau de Física, Facultat de Física, Universitat de Barcelona, Any: 2015, Tutor: Jorge Torra, We study the environment of bright stars detected and stored by the Gaia satellite. The main goal is to determine how the environment is related to the real stars. This study will allow us to select the best values to identify these detections in the algorithm.

[spa] Gaia es un proyecto de la agencia espacial Europea (ESA) que pretende hacer un censo galáctico catalogando más de 1000 millones de objetos con una precisión astrometrica sin precedentes. La astrometria es la parte de la astronomia dedicada a la medida y al estudio del movimiento de los astros y ha sido uno de los principales motores de la física y las matemáticas de los últimos 2000 años. La precisión astrometrica de Gaia se estima en unos 10 microsegundos de arco, que es el tamaño angular de una moneda de dos euros en la superficie de la Luna vista desde la Tierra. A tal precisión, un montón de efectos en la propagación de la luz y la definición de los observables astrometricos entran en juego. Por ejemplo, la deflexión de la luz por el Sol pero también de los planetas del sistema solar, efectos de aberración en las imágenes adquiridas por la sonda debido a su rotación, o nuevos efectos astrométricos de segundo orden en el movimiento de las fuentes previamente indetectables. Este trabajo estudia estos aspectos desde un punto de vista relativista. Contiene tres partes. La primera se dedica a los efectos en la adquisición de datos astrometricos debidos a la propagación pro el interior de un sistema óptico en rotación (tipo Gaia). La segunda parte versa sobre la relaicón entre el intervalo de tiempo de emisión y de recepción, que causa movimiento aparente adicional sobre todo el movimiento de la sonda es no-lineal. La tercera parte estudia la deflexión dela luz relativista por parte de los planetas del sistema solar y se estudia la calidad así como el método de extracción de parámetros físicos a partir de la observaciones.

EN CASTELLANO:En este trabajo se ha realizado un estudio de la estructura espacial y cinemática de la componente estelar joven de la Galaxia en el entorno solar en tres escalas diferentes, que han permitido estudiar la estructura espiral galáctica, el Cinturón de Gould y la componente estelar joven en el entorno solar más cercano.Se han construido tres muestras de estrellas con datos procedentes del catálogo Hipparcos. La primera de ellas está formada por estrellas de los tipos espectrales O y B, y contiene información astrométrica, fotométrica, velocidades radiales y diversos parámetros físicos de las estrellas, incluyendo la edad. La segunda muestra contiene todas las estrellas variables cefeidas del catálogo Hipparcos, con información astrométrica, distancias calculadas a partir de dos calibraciones periodo-luminosidad y velocidades radiales. Finalmente, se ha recopilado toda la información existente hasta la fecha en la bibliografía referente a las asociaciones locales jóvenes que han sido descubiertas en el entorno solar más cercano durante los últimos años.A partir de las muestras de estrellas que se han construido se ha estudiado, en primer lugar, la estructura espiral de la Galaxia. Los resultados más destacados en este apartado son que el Sol se encuentra situado en la parte externa del brazo espiral más cercano y fuera del círculo de corrotación. Ambos resultados pueden tener una gran importancia en la historia de la formación estelar reciente en el entorno solar. También se ha obtenido un valor negativo (y significativo) para la divergencia del campo de velocidades (término K). Los resultados obtenidos han sido validados a través de unas simulaciones, que han permitido obtener una estimación externa de los errores y una evaluación de los sesgos que afectan a los diferentes parámetros obtenidos.A una escala a 1 kpc de distancia heliocéntrica, la estructura dominante en el entorno solar es el denominado Cinturón de Gould, que contiene la mayor parte de las estrellas jóvenes y nubes de polvo y gas de esta región. En nuestro trabajo hemos obtenido los parámetros de orientación del Cinturón y se ha estudiado su peculiar cinemática, tras la realización de unas simulaciones con los mismos objetivos que las mencionadas anteriormente. Se ha obtenido que las estrellas del complejo de Scorpio-Centaurus (Sco-Cen) presentan una cinemática que no se ajusta a la prevista por los diversos modelos que intentan explicar la evolución cinemática del Cinturón. También se ha obtenido que el movimiento de expansión de esta estructura no parece ser un efecto global, ya que se restringe a los primeros ~250 pc de distancia heliocéntrica.Finalmente, el estudio de la integración de las órbitas hacia atrás en el tiempo de las asociaciones locales jóvenes y de los miembros del complejo de Sco-Cen nos ha permitido inferir que las primeras no se formaron en el interior de este complejo, sino en pequeñas nubes moleculares situadas en sus alrededores, y que previamente habían sido expulsadas. Por otro lado, se ha visto que alguna supernova de estas asociaciones locales jóvenes fue probablemente la responsable del recalentamiento de la Burbuja Local hace unos pocos millones de años. Finalmente, teniendo en cuenta los resultados obtenidos en diversos apartados de este trabajo, se ha propuesto un escenario para la formación estelar reciente en el entorno solar a partir del impacto de una gran nube molecular con el brazo espiral interno, que dio lugar, en diferentes fases, al complejo de Sco-Cen y a las asociaciones locales jóvenes., Title: "On the spatial and kinematic structure of the young stellar component in the solar neighbourhood" Text: The spatial and kinematic structure of the young stellar component in the solar neighbourhood has been analysed on three different scales, which have allowed the study of the galactic spiral structure, the Gould Belt, and the young stellar component in the solar neighbourhood.Three stellar samples have been constructed with data coming from the Hipparcos catalogue. The first one is composed of O- and B-type stars, and contains not only the astrometric data from Hipparcos but also other relevant astrophysical data. The second sample contains all the Hipparcos Cepheid stars with astrometry, distances and radial velocities. Finally, the third sample compiles all the information published in the literature on the young local associations that have been discovered in the solar neighbourhood over the last years.From these stellar samples we have studied, firstly, the galactic spiral structure. The most important results in this section are the location of the Sun at the external side of the nearest spiral arm and outside the corotation circle. We have also obtained a negative (and significant) value for the divergence of the velocity field (K term). Our results have been checked through a set of simulations that have made possible an external estimation of the errors and an evaluation of the biases affecting the obtained parameters. The most important structure present in the solar neighbourhood at a 1-kpc scale is the so-called Gould Belt. We have derived the orientation parameters of the Gould Belt and studied its peculiar kinematics, after carrying out a set of simulations. We have found that the stars belonging to the Scorpio-Centaurus (Sco-Cen) complex present a kinematic behaviour that is not well explained in the frame of the several models proposed for the kinematic evolution of the Belt. We have also found that the expansion motion of this structure does not seem to be a large-scale effect, since it is only observed in the first ~250 pc from the Sun.The integration of the orbits back in time for the young local associations and the members of the Sco-Cen complex has led to the conclusion that the former were not born inside this complex, but in previously-ejected small molecular clouds. Also, we presume that some supernovae from these associations could be responsible for the heating of the Local Bubble a few million years ago. Finally, the scenario for the recent star formation in the solar neighbourhood proposed is the impact of a large molecular cloud with the internal spiral arm, which produced, on different phases, the birth of the Sco-Cen complex and the young local associations.

En el entorno solar encontramos estrellas de características físicas muy diferentes, pertenecientes a dos de las componentes estelares que forman la Galaxia: el disco (delgado y grueso) y el halo. Los datos astrométricos del catálogo Hipparcos de estrellas enanas FGK combinados con la fotometría infrarroja del catálogo 2MASS han permitido la determinación de los parámetros (cinemática, metalicidad, edad y luminosidad) de cada una de estas componentes en el entorno solar y establecer las posibles dependencias de estos parámetros con la temperatura y/o la metalicidad. En todo el proceso se ha puesto especial atención al correcto tratamiento de los errores y sesgos observacionales que se hayan podido introducir en la selección de las estrellas que forman nuestra muestra. La muestra construida contiene más de 11000 estrellas con datos astrométricos del catálogo Hipparcos, medidas de la velocidad radial (en un 20% de los casos) y fotometría en las bandas BV del visible y HK del infrarrojo, además de los colores del sistema Strömgren. Parte de esta fotometría se obtuvo en diversas campañas observacionales llevadasa cabo en el telescopio del OAN del Observatorio de Calar Alto y en el Telescopio Carlos Sánchezdel Observatorio del Teide. La fotometría se utilizó para obtener algunos de los parámetros físicos de las estrellas (metalicidad, gravedad superficial, temperatura) y una estimación del enrojecimiento estelar.Para la determinación de la temperatura se ha utilizado la fotometría en las bandas VJHK. El método que hemos desarrollado se basa en la comparación entre la fotometría observada y la fotometría sintética calculada para cada una de estas bandas a partir de los modelos de atmósferas estelares. El método,aplicable a estrellas entre los 4000 K y los 8000 K, proporciona la temperatura y el semidiámetro angular, con unos errores estimados del orden del 1.5% y 2%, respectivamente. La aplicación del método a las 11000 estrellas de la muestra permite establecer una calibración de la temperatura en función del color (V-K)0 y de la metalicidad, con una dispersión de 20 K. A partir de la temperatura y el semidiámetro angular se han calculado también las correcciones bolométricas en las bandas V y K2MASS y establecido calibraciones en función de los mismos parámetros que en el caso de la temperatura. En este caso las dispersiones obtenidas son de 0.005 magnitudes.La muestra se supuso formada por estrellas pertenecientes al disco delgado, disco grueso o halo.Las propiedades de cada una de estas componentes se obtuvieron a través del ajuste por máxima verosimilitud de un modelo de la muestra que incluía, además de las características físicas de la población de la cual ha sido extraída la muestra, los procesos de selección y los errores observacionales. Ello proporcionó los valores medios de la cinemática y metalicidad de cada componente galáctica, una calibración de su magnitud absoluta en función del color (V-K)0 y una estimación (corregida de sesgos observacionales) de la distancia individual a cada estrella. Las edades de cada componente fueron estimadas mediante el ajuste de isócronas teóricas en el diagrama HR, utilizando en el eje de luminosidades una determinación no sesgada de la misma calculada a partir de la distancia corregida de sesgos y de la corrección bolométrica.Los resultados obtenidos muestran un halo con una edad de entre 12.5 y 13.5 Ga y metalicidad promedio[Fe/H]=-1.5; un disco grueso con una edad entre 10 y 12 Ga y [Fe/H]=-0.63, y un disco delgado que ha sido divido en dos subcomponentes jóvenes (edad inferior a 10 Ga), ambas de metalicidad solar pero con cinemática algo diferente, y una componente ligeramente más vieja y menos metáica que las anteriores. Por su parte los valores de la cinemática, en buen acuerdo con trabajos recientes basados también en datos Hipparcos, indican la existencia de una relación de ésta con la edad y la metalicidad.ENGLISH, The stars in the solar neighborhood belong to two different stellar components: the disk (thin and thick) and the halo. Astrometric data from Hipparcos catalog for FGK type stars, together with 2MASS infrared photometry, have allowed to determine the physical properties(kinematics, metallicity, age and luminosity) of those components, and to study their dependences with the temperature and/or metallicity. We focused the effort in a correct treatment of the observational errors and biases.Our sample contains more than 11000 stars with astrometric data, radial velocity (for 20% of the sample) and photometry in the BVJHK and Strömgren bands. The photometry was used to obtainthe metallicity, surface gravity and temperature of each star, together with an estimation of the interstellar absortion.The temperature was calculated from VJHK photometry. Our method compares the observed photometry with synthetic photometry from the stellar atmosphere models. The method can be applied between 4000 and 8000 K and gets both the effective temperature and the angular semi-diameter,with an error about 1.5% and 2.0%, respectively. It also gets the bolometric correction in each band. The application to the stars of our sample allows to establish a calibration of the temperature and the bolometric correction in the V and K{2MASS) bands as function of the (V-K) color and the metallicity.The properties of each galactic component (thin and thick disc and halo)were obtained fitting a model of our sample (including physical properties, selection process and observational errors) using a maximum likelihood method.In this way we obtained, for each component, the mean values of the kinematics and metallicity, a calibration of the absolute magnitude as function of the (V-K) and metallicity, and an unbiased estimation of the individual distance. Finally, a fit of theoretical isochrones on the HRdiagram of the different components allows to determine their age.The results show that the age of the halo is between 12.5 and 13.5 Gy and has a mean metallicity equal to -1.5; the age of the thick disk is between 10 and 12 Gy ([Fe/H]=-0.63); the thin disk seems to have two subcomponents with age less than 10 Gy, both of solar metallicity but different kinematics, and a third components, slightly older and with smaller metallicity.The values obtained for the kinematic are in good agreement with recent works, showing a kinematic-age-metallicity relation.