<i>Gaia</i> Data Release 1. Summary of the astrometric, photometric, and survey properties

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 of 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−1 for the proper motions. A systematic component of ∼0.3 mas should be added to the parallax uncertainties. 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 five-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

Gaia Data Release 1: Testing parallaxes with local Cepheids and RR Lyrae stars

Context. Parallaxes for 331 classical Cepheids, 31 Type II Cepheids, and 364 RR Lyrae stars in common between Gaia and the Hipparcos and Tycho-2 catalogues are published in Gaia Data Release 1 (DR1) as part of the Tycho-Gaia Astrometric Solution (TGAS). Aims. In order to test these first parallax measurements of the primary standard candles of the cosmological distance ladder, which involve astrometry collected by Gaia during the initial 14 months of science operation, we compared them with literature estimates and derived new period-luminosity (PL), period-Wesenheit (PW) relations for classical and Type II Cepheids and infrared PL, PL-metallicity (PLZ), and optical luminosity-metallicity (M V -[Fe/H]) relations for the RR Lyrae stars, with zero points based on TGAS. Methods. Classical Cepheids were carefully selected in order to discard known or suspected binary systems. The final sample comprises 102 fundamental mode pulsators with periods ranging from 1.68 to 51.66 days (of which 33 with σ Ω /Ω < 0.5). The Type II Cepheids include a total of 26 W Virginis and BL Herculis stars spanning the period range from 1.16 to 30.00 days (of which only 7 with σ Ω /Ω < 0.5). The RR Lyrae stars include 200 sources with pulsation period ranging from 0.27 to 0.80 days (of which 112 with σ Ω /Ω < 0.5). The new relations were computed using multi-band (V,I,J,K s ) photometry and spectroscopic metal abundances available in the literature, and by applying three alternative approaches: (i) linear least-squares fitting of the absolute magnitudes inferred from direct transformation of the TGAS parallaxes; (ii) adopting astrometry-based luminosities; and (iii) using a Bayesian fitting approach. The last two methods work in parallax space where parallaxes are used directly, thus maintaining symmetrical errors and allowing negative parallaxes to be used. The TGAS-based PL,PW,PLZ, and M V - [Fe/H] relations are discussed by comparing the distance to the Large Magellanic Cloud provided by different types of pulsating stars and alternative fitting methods. Results. Good agreement is found from direct comparison of the parallaxes of RR Lyrae stars for which both TGAS and HST measurements are available. Similarly, very good agreement is found between the TGAS values and the parallaxes inferred from the absolute magnitudes of Cepheids and RR Lyrae stars analysed with the Baade-Wesselink method. TGAS values also compare favourably with the parallaxes inferred by theoretical model fitting of the multi-band light curves for two of the three classical Cepheids and one RR Lyrae star, which were analysed with this technique in our samples. The K-band PL relations show the significant improvement of the TGAS parallaxes for Cepheids and RR Lyrae stars with respect to the Hipparcos measurements. This is particularly true for the RR Lyrae stars for which improvement in quality and statistics is impressive. Conclusions. TGAS parallaxes bring a significant added value to the previous Hipparcos estimates. The relations presented in this paper represent the first Gaia-calibrated relations and form a work-in-progress milestone report in the wait for Gaia-only parallaxes of which a first solution will become available with Gaia Data Release 2 (DR2) in 2018. © ESO, 2017

Gaia Data Release 1: Open cluster astrometry: performance, limitations, and future prospects

Context. The first Gaia Data Release contains the Tycho-Gaia Astrometric Solution (TGAS). This is a subset of about 2 million stars for which, besides the position and photometry, the proper motion and parallax are calculated using Hipparcos and Tycho-2 positions in 1991.25 as prior information.Aims. We investigate the scientific potential and limitations of the TGAS component by means of the astrometric data for open clusters.Methods. Mean cluster parallax and proper motion values are derived taking into account the error correlations within the astrometric solutions for individual stars, an estimate of the internal velocity dispersion in the cluster, and, where relevant, the effects of the depth of the cluster along the line of sight. Internal consistency of the TGAS data is assessed.Results. Values given for standard uncertainties are still inaccurate and may lead to unrealistic unit-weight standard deviations of least squares solutions for cluster parameters. Reconstructed mean cluster parallax and proper motion values are generally in very good agreement with earlier HIPPARCOS-based determination, although the Gaia mean parallax for the Pleiades is a significant exception. We have no current explanation for that discrepancy. Most clusters are observed to extend to nearly 15 pc from the cluster centre, and it will be up to future Gaia releases to establish whether those potential cluster-member stars are still dynamically bound to the clusters.Conclusions. The Gaia DR1 provides the means to examine open clusters far beyond their more easily visible cores, and can provide membership assessments based on proper motions and parallaxes. A combined HR diagram shows the same features as observed before using the HIPPARCOS data, with clearly increased luminosities for older A and F dwarfs

The Gaia mission

Gaia is a cornerstone mission in the science programme of the EuropeanSpace 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. http://www.cosmos.esa.int/gai

Taquínidos (Diptera) capturados en trampas para trampeo masivo de Bactrocera oleae (Rossi) (Diptera: Tephritidae) en olivares del centro de España

Tachinid flies are important for biological control of pests, because most species are parasitoids of insects. The objectives of this work were 1) to describe the species of tachinid flies captured by mass trapping devices against the olive fruit fly, Bactrocera oleae, in olive groves in Central Spain, and 2) to report on the selectivity of the different devices for this important group of insects. The study was carried out in two olive groves in the province of Madrid during 2005 and 2008. The number of trapping devices was five in 2005 and twelve in 2008. A total of 66 species of tachinid flies was captured. Comments on some of them are provided because of their special interest. Three tachinid species (Clemelis massilia, Schembria meridionalis and Ceromya flaviseta) are recorded from the Iberian Peninsula for the first time. It is remarkable that captures of C. massilia accounted for 72.3% in 2008. Comparison of the different mass-trapping devices indicates that none of them is selective for this important family of parasitoids. Numbers of tachinid flies captured per trap and season ranged between 1 and 13 in 2005, and 24 and 283 in 2008. This is the first study carried out in Spain on tachinids captured by mass-trapping devices and it reports the abundance and species diversity of this group of insects in olive groves as well as the poor selectivity of mass-trapping on themLos taqu&iacute;nidos son importantes para el control biol&oacute;gico de plagas, ya que en su mayor&iacute;a son parasitoides de insectos. Los objetivos de este trabajo fueron: 1) describir las especies de taqu&iacute;nidos capturados por dispositivos de trampeo masivo para la mosca del olivo, Bactrocera oleae, en olivares del centro de Espa&ntilde;a, y 2) conocer la selectividad de los distintos dispositivos para este grupo de insectos. El estudio se llev&oacute; a cabo durante 2005 y 2008 en dos olivares de la provincia de Madrid. Se emplearon cinco dispositivos de trampeo masivo en 2005 y doce en 2008. El n&uacute;mero total de especies de taqu&iacute;nidos capturadas fue 66. Algunas de ellas se comentan en detalle en virtud de su especial inter&eacute;s. Se cita por primera vez la presencia en la Pen&iacute;nsula Ib&eacute;rica de tres especies de taqu&iacute;nidos (Clemelis massilia, Schembria meridionalis y Ceromya flaviseta). Es destacable que el 72,3% de las capturas en 2008 fue de C. massilia. La comparaci&oacute;n de los diferentes dispositivos de trampeo masivo indica que ninguno de ellos es selectivo para este importante grupo de parasitoides. El n&uacute;mero de taqu&iacute;nidos capturados por trampa y temporada vari&oacute; entre 1 y 13 en 2005, y entre 24 y 283 en 2008. Este es el primer estudio llevado a cabo en Espa&ntilde;a sobre taqu&iacute;nidos capturados por dispositivos de trampeo masivo e indica la abundancia y diversidad de especies de estos insectos en los olivares, as&iacute; como la pobre selectividad del trampeo masivo frente a ello

Thermally and anionically initiated cure of bismaleimide monomers

International audienceA kinetic and thermodynamic study of the thermally or anionically induced cure of aromatic bismaleimide monomers (namely 2,4-bismaleimidotoluene, 4,4'-bismaleimidodiphenylmethane and their eutectic mixture) is presented. Calorimetric investigations allowed the determination of heats of polymerization and activation energies for both types of initiations, and the values found are compared with data in the literature. Isothermal cures were also carried out with and without anionic initiator (typically imidazole). SEC measurements were used to monitor the conversion of the monomers as a function of time. The thermally induced polymerization seems to proceed in a rather heterogeneous way, owing to an initiation that is too slow: gelation appears at first only as the formation of microgels, with no immediate increase in the viscosity; macrogelation occurs some time after. On the contrary, the anionically induced polymerization is more homogeneous. A complete study of a particular reacting system revealed no interference between radical and anionic polymerization over a wide range of temperatures, and in this case gelation results in an immediate increase in viscosity. However, the conversion at the gel point is unexpectedly high, which can be interpreted as the result of a very fast initiation as well as of transfer reactions. Glass transition temperatures were also measured as a function of time and curing temperature in order to study the influence of vitrification on the kinetics and to check for the existence of a unique relation between Tg and conversion. This actually proved to be correct as long as diffusion does not slow down the reaction; in this case Gillham's treatment of Tg versus Int was successfully applied and led to the correct value of the activation energy. All the measurements allowed us to establish the time-temperature-transformation cure diagram for a specific reacting system

Thermally and anionically initiated cure of bismaleimide monomers

International audienceA kinetic and thermodynamic study of the thermally or anionically induced cure of aromatic bismaleimide monomers (namely 2,4-bismaleimidotoluene, 4,4'-bismaleimidodiphenylmethane and their eutectic mixture) is presented. Calorimetric investigations allowed the determination of heats of polymerization and activation energies for both types of initiations, and the values found are compared with data in the literature. Isothermal cures were also carried out with and without anionic initiator (typically imidazole). SEC measurements were used to monitor the conversion of the monomers as a function of time. The thermally induced polymerization seems to proceed in a rather heterogeneous way, owing to an initiation that is too slow: gelation appears at first only as the formation of microgels, with no immediate increase in the viscosity; macrogelation occurs some time after. On the contrary, the anionically induced polymerization is more homogeneous. A complete study of a particular reacting system revealed no interference between radical and anionic polymerization over a wide range of temperatures, and in this case gelation results in an immediate increase in viscosity. However, the conversion at the gel point is unexpectedly high, which can be interpreted as the result of a very fast initiation as well as of transfer reactions. Glass transition temperatures were also measured as a function of time and curing temperature in order to study the influence of vitrification on the kinetics and to check for the existence of a unique relation between Tg and conversion. This actually proved to be correct as long as diffusion does not slow down the reaction; in this case Gillham's treatment of Tg versus Int was successfully applied and led to the correct value of the activation energy. All the measurements allowed us to establish the time-temperature-transformation cure diagram for a specific reacting system

l controllo di qualità per i trattamenti di pulitura: una proposta metodologica di cantiere

Lo stimolo per la predisposizione di un metodo di valutazione della qualità delle operazioni di pulitura, o di descialbo in questo caso, nasce in concomitanza con l’apertura del cantiere di restauro volto al recupero e alla valorizzazione delle pitture murali del donjon del castello di Quart. L’intento principale è stato quello di individuare un metodo che permettesse di monitorare e valutare oggettivamente la qualità della pulitura. Lo studio ha quindi riguardato l’identificazione di tecniche strumentali applicabili in situ e verificabili con il supporto di classiche tecniche di laboratorio atte a valutare l’andamento dei lavori e la qualità degli stessi. Le tecniche messe a punto hanno permesso di affrontare le situazioni di rischio per il tipo di pulitura selezionato e di predisporre un protocollo di misura atto a valutare la qualità e l’omogeneità degli interventi. Le strumentazioni impiegate per questo tipo di studio sono state il colorimetro, lo spettrofotometro FORS, la microscopia di cantiere e la microscopia di laboratorio. Il lavoro presenterà i risultati e le applicazioni di queste tecniche allo scopo del controllo dei metodi di pulitura

Tachinidae (Diptera) collected in traps used for mass-trapping of Bactrocera oleae (Rossi) (Diptera: Tephritidae) in olive groves in Central Spain

Tachinid flies are important for biological control of pests, because most species are parasitoids of insects. The objectives of this work were 1) to describe the species of tachinid flies captured by mass trapping devices against the olive fruit fly, Bactrocera oleae, in olive groves in Central Spain, and 2) to report on the selectivity of the different devices for this important group of insects. The study was carried out in two olive groves in the province of Madrid during 2005 and 2008. The number of trapping devices was five in 2005 and twelve in 2008. A total of 66 species of tachinid flies was captured. Comments on some of them are provided because of their special interest. Three tachinid species (Clemelis massilia, Schembria meridionalis and Ceromya flaviseta) are recorded from the Iberian Peninsula for the first time. It is remarkable that captures of C. massilia accounted for 72.3% in 2008. Comparison of the different mass-trapping devices indicates that none of them is selective for this important family of parasitoids. Numbers of tachinid flies captured per trap and season ranged between 1 and 13 in 2005, and 24 and 283 in 2008. This is the first study carried out in Spain on tachinids captured by mass-trapping devices and it reports the abundance and species diversity of this group of insects in olive groves as well as the poor selectivity of mass-trapping on the