The accretion rates and mechanisms of Herbig Ae/Be stars

This work presents a spectroscopic study of 163 Herbig Ae/Be stars. Amongst these, we present new data for 30 objects. Stellar parameters such as temperature, reddening, mass, luminosity, and age are homogeneously determined. Mass accretion rates are determined from Hα emission line measurements. Our data is complemented with the X-Shooter sample from previous studies and we update results using Gaia DR2 parallaxes giving a total of 78 objects with homogeneously determined stellar parameters and mass accretion rates. In addition, mass accretion rates of an additional 85 HAeBes are determined. We confirm previous findings that the mass accretion rate increases as a function of stellar mass, and the existence of a different slope for lower and higher mass stars, respectively. The mass where the slope changes is determined tobe 3.98+1.37−0.94M⊙⁠. We discuss this break in the context of different modes of disc accretion for low- and high-mass stars. Because of their similarities with T Tauri stars, we identify the accretion mechanism for the late-type Herbig stars with the Magnetospheric Accretion. The possibilities for the earlier-type stars are still open, we suggest the Boundary Layer accretion model may be a viable alternative. Finally, we investigated themass accretion–age relationship. Even using the superior Gaia based data, it proved hard to select a large enough sub-sample to remove the mass dependence in this relationship. Yet, it would appear that the mass accretion does decline with age as expected from basic theoretical considerations

Cambios en el uso del preservativo en una cohorte de prostitutas

ResumenObjetivoDescribir los cambios en el uso del preservativo en una cohorte de mujeres que ejercen la prostitución en Alicante y analizar los factores que se relacionan con los cambios en esta práctica preventiva.MétodosSe han usado los datos de un estudio prospectivo que incluyó a las mujeres dedicadas a la prostitución que acudieron al Centro de Información y Prevención de Sida (CIPS) de Alicante desde 1986 a 1996. Se estimó la frecuencia en el uso del preservativo con los clientes en la primera y última visita al centro, se valoró el cambio entre las dos visitas y los factores asociados a ellos. Se realizaron dos análisis de regresión logística para determinar la asociación entre el cambio positivo o negativo y las variables explicativas.ResultadosLa prevalencia de uso del preservativo en la última visita fue mayor que en la primera (83,9% frente al 69,2%; p < 0,001). Entre las prostitutas que trabajan en contactos se incrementa más de cinco veces el uso del preservativo que entre las que lo hacen en los clubs y en la calle. Las que tienen mayor tiempo de seguimiento son las que tienen una mayor prevalencia en el uso del preservativo al final del seguimiento (odds ratio ajustada > 6 años frente a < de un año = 7,61; intervalo de confianza [IC] del 95%: 2,2-26,0).ConclusiónEste estudio ha puesto en evidencia un incremento en la frecuencia del uso del preservativo y la baja frecuencia de su abandono en una cohorte de prostitutas a lo largo de 10 años. En un futuro será necesario adaptar esta estrategia preventiva a las nuevas formas de prostitución menos estables y al incremento de inmigrantes, factores que motivan una menor asistencia y adhesión a centros de prevención.SummaryObjetiveTo describe changes in condom use among prostitutes enrolled in a prospective cohort study in Alicante (Spain), and to identify those factors associated with changes in this behaviour.MethodsData from this study come from a prospective cohort study of women working at prostitution enrolled in a center for AIDS preventive at Alicante from 1986 to 1996. The proportion of condom use by prostitutes with their clients was recorded during the first visit and the last one, and changes in condom use were estimated as the difference between them. Two logistic regression analyses were done to identify those factors associated with positive or negative changes in condom use.ResultsA statistically significant increase in the prevalence of condom use was observed between the first, 69,2%, and the last visit, 83,9% (p < 0,001). Prostitutes working private increased the condom use more than five time than those working in clubs or at the street. The higher the follow-up time the higher the prevalence of condom user, OR > 6 years = 7,6 (95% CI: 2,2-26,0). No variable was associated with a negative change in condom use.ConclusionThis study shows an overall increase of condom use in a cohort of prostitutes after 10 years of follow-up. Relapse in risk behavior has been infrequent. In the future, preventive strategies to increase the use of condoms among prostitutes should be adapted to the new forms of sexual commerce

Radiological evaluation associated to the mining and concentration of monazite in Central Spain

Trabajo presentado a la 4th International Conference on Environmental Radioactivity: Radionuclides as Tracers of Environmental Processes, celebrada en Vilnius (Lithuania) del 29 de mayo al 2 de junio de 2017.A detailed radiological evaluation (occupational, public and environmental) has been performed associated with the mining and physical concentration of monazite, enriched in different rare earths, in a zone to be exploited commercially which is located 200 km at the south of Madrid (Spain). This evaluation is performed because the rare earth extraction mining and concentration steps are activities recognized in the positive list of NORM activities to be analysed for possible adoption of radiological controls.Peer reviewe

Catalogue of new Herbig Ae/Be and classical Be stars - A machine learning approach to Gaia DR2

Context. The intermediate-mass pre-main sequence Herbig Ae/Be stars are key to understanding the differences in formation mechanisms between low- and high-mass stars. The study of the general properties of these objects is hampered by the lack of a well-defined, homogeneous sample, and because few and mostly serendipitously discovered sources are known. Aims. Our goal is to identify new Herbig Ae/Be candidates to create a homogeneous and well defined catalogue of these objects. Methods. We have applied machine learning techniques to 4 150 983 sources with data from Gaia DR2, 2MASS, WISE, and IPHAS or VPHAS+. Several observables were chosen to identify new Herbig Ae/Be candidates based on our current knowledge of this class, which is characterised by infrared excesses, photometric variabilities, and Hα emission lines. Classical techniques are not efficient for identifying new Herbig Ae/Be stars mainly because of their similarity with classical Be stars, with which they share many characteristics. By focusing on disentangling these two types of objects, our algorithm has also identified new classical Be stars. Results. We have obtained a large catalogue of 8470 new pre-main sequence candidates and another catalogue of 693 new classical Be candidates with a completeness of 78.8 ± 1.4% and 85.5 ± 1.2%, respectively. Of the catalogue of pre-main sequence candidates, at least 1361 sources are potentially new Herbig Ae/Be candidates according to their position in the Hertzsprung-Russell diagram. In this study we present the methodology used, evaluate the quality of the catalogues, and perform an analysis of their flaws and biases. For this assessment, we make use of observables that have not been accounted for by the algorithm and hence are selection-independent, such as coordinates and parallax based distances. The catalogue of new Herbig Ae/Be stars that we present here increases the number of known objects of the class by an order of magnitude

Relation between metallicities and spectral energy distributions of Herbig Ae/Be stars. A potential link with planet formation

(Abridged) The stellar metallicity, [M/H], may have important implications for planet formation. In particular, Kama et al. proposed that the deficit of refractory elements in the surfaces of some Herbig Ae/Be stars (HAeBes) may be linked to the presence of disk cavities likely caused by Jovian planets that trap the metal-rich content. This work aims to provide a robust test on the previous proposal by analyzing the largest sample of HAeBes with homogeneously derived [M/H] values, stellar, and circumstellar properties. [M/H] values of 67 HAeBes were derived based on observed spectra and Kurucz synthetic models. Statistical analyses were carried out aiming to test the potential relation between [M/H] and the group I sources from the spectral energy distribution (SED) classification by Meeus et al., associated to the presence of cavities potentially carved by giant planets. Our study robustly confirms that group I sources tend to have a lower [M/H] than that of group II HAeBes. A similar analysis involving SED-based transitional disks does not reveal such a relation, indicating that not all processes capable of creating dust holes have an effect on the stellar abundances. We also show that the observed [M/H] differences are not driven by environmental effects. Finally, group I sources tend to have stronger (sub-) mm continuum emission presumably related to the presence of giant planets. Indeed, literature results indicate that disk substructures probably associated to their presence are up to ten times more frequent in group I HAeBes. We provide indirect evidences suggesting that giant planets are more frequent around group I/low [M/H] stars than around the rest of the HAeBes. However, the direct test requires multiple detections of forming planets in their disks, so far limited to the candidate around the metal depleted ([M/H] = -0.35 +- 0.25) group I HAeBe star AB Aur.Comment: 16 pages, 10 figures, 2 tables. Accepted in A&

Nutritional and functional characteristics of Erophaca baetica seeds, a legume endemic to the Mediterranean region

<i>Erophaca baetica</i> is a legume endemic to the Mediterranean region. Although the fruits and seeds are large, the presence of the “locoism” which produces the alkaloid, swainsonine has prevented its use as animal feed or for human nutrition. Their protein content and chromatographic profile, amino acid composition, fatty acid composition, and polyphenol contents have been determined in order to explore the potential of the <i>E. baetica</i> seeds as a source of dietary protein with functional components. The protein content was found to be 36% (w/w), and an amino acid analysis revealed a deficiency in sulphur amino acids, tryptophane, and lysine. The low lysine content is probably due to the abundance of alkaloids metabolically derived from this amino acid. Oleic and linoleic acids are the major fatty acids in the seeds. The antioxidant activity of polyphenol extracts was higher than the activity of the polyphenols extracted from most edible legume seeds. Hence, <i>E. baetica</i> seeds represent a promising source of functional and nutritional components on the condition that the anti-nutritional alkaloids are previously removed.<br><br><i>Erophaca baetica</i> es una leguminosa endémica de la región mediterránea. Aunque los frutos y las semillas son grandes, la presencia del alcaloide swainsonina causante de locoismo, ha impedido su uso como alimento para animales o para nutrición humana. El contenido proteico y su perfil cromatográfico, la composición de aminoácidos, de ácidos grasos, y contenido de polifenoles se han determinado con el fin de explorar el potencial de las semillas de <i>E. baetica</i> como una fuente de proteínas y de componentes funcionales de la dieta. El contenido de proteínas es del 36% (w / w), y el análisis de aminoácidos reveló deficiencia en aminoácidos azufrados, triptófano y lisina. El contenido de lisina bajo es probablemente debido a la abundancia de alcaloides metabólicamente derivados de este aminoácido. Los ácidos oleicos y linoleico son los principales ácidos grasos en las semillas. La actividad antioxidante de los extractos de polifenoles fue mayor que la actividad de los polifenoles extraídos de la mayoría de las semillas de leguminosas comestibles. Por lo tanto, las semillas de <i>E. baetica</i> representan una fuente interesante de componentes funcionales y nutricionales con la condición de que los alcaloides antinutricionales sean quitados antes

Gaia DR2 study of Herbig Ae/Be stars

Aims. We use Gaia Data Release 2 (DR2) to place 252 Herbig Ae/Be stars in the Hertzsprung–Russell diagram and investigate their characteristics and properties. Methods. For all known Herbig Ae/Be stars with parallaxes in Gaia DR2, we collected their atmospheric parameters and photometric and extinction values from the literature. To these data we added near-infrared and mid-infrared photometry, and collected Hα emission line properties such as equivalent widths and line profiles, and their binarity status. In addition, we developed a photometric variability indicator from Gaia’s DR2 information. Results. We provide masses, ages, luminosities, distances, photometric variabilities and IR excesses homogeneously derived for the most complete sample of Herbig Ae/Be stars to date. We find that high-mass stars have a much smaller IR excess and have much lower optical variabilities compared to lower-mass stars, with the break at around 7 M⊙. Hα emission is generally correlated with IR excess, with the correlation being stronger for IR emission at wavelengths tracing the hot dust closest to the star. The variability indicator as developed by us shows that ∼25% of all Herbig Ae/Be stars are strongly variable. We observe that the strongly variable objects display doubly peaked Hα line profiles, indicating an edge-on disk. Conclusions. The fraction of strongly variable Herbig Ae stars is close to that found for A-type UX Ori stars. It had been suggested that this variability is in most cases due to asymmetric dusty disk structures seen edge-on. The observation here is in strong support of this hypothesis. Finally, the difference in dust properties occurs at 7 M⊙, while various properties traced at UV/optical wavelengths differ at a lower mass, 3 M⊙. The latter has been linked to different accretion mechanisms at work, whereas the differing IR properties and photometric variabilities are related to different or differently acting (dust-)disk-dispersal mechanisms

Características nutricionales y funcionales de semillas de Erophaca baetica, una leguminosa endémica de la región Mediterránea

Erophaca baetica is a legume endemic to the Mediterranean region. Although the fruits and seeds are large, the presence of the “locoism” which produces the alkaloid, swainsonine has prevented its use as animal feed or for human nutrition. Their protein content and chromatographic profile, amino acid composition, fatty acid composition, and polyphenol contents have been determined in order to explore the potential of the E. baetica seeds as a source of dietary protein with functional components. The protein content was found to be 36% (w/w), and an amino acid analysis revealed a deficiency in sulphur amino acids, tryptophane, and lysine. The low lysine content is probably due to the abundance of alkaloids metabolically derived from this amino acid. Oleic and linoleic acids are the major fatty acids in the seeds. The antioxidant activity of polyphenol extracts was higher than the activity of the polyphenols extracted from most edible legume seeds. Hence, E. baetica seeds represent a promising source of functional and nutritional components on the condition that the anti-nutritional alkaloids are previously removed.Erophaca baetica es una leguminosa endémica de la región mediterránea. Aunque los frutos y las semillas son grandes, la presencia del alcaloide swainsonina causante de locoismo, ha impedido su uso como alimento para animales o para nutrición humana. El contenido proteico y su perfil cromatográfico, la composición de aminoácidos, de ácidos grasos, y contenido de polifenoles se han determinado con el fin de explorar el potencial de las semillas de E. baetica como una fuente de proteínas y de componentes funcionales de la dieta. El contenido de proteínas es del 36% (w / w), y el análisis de aminoácidos reveló deficiencia en aminoácidos azufrados, triptófano y lisina. El contenido de lisina bajo es probablemente debido a la abundancia de alcaloides metabólicamente derivados de este aminoácido. Los ácidos oleicos y linoleico son los principales ácidos grasos en las semillas. La actividad antioxidante de los extractos de polifenoles fue mayor que la actividad de los polifenoles extraídos de la mayoría de las semillas de leguminosas comestibles. Por lo tanto, las semillas de E. baetica representan una fuente interesante de componentes funcionales y nutricionales con la condición de que los alcaloides antinutricionales sean quitados antes

Planet formation in intermediate-separation binary systems

ABSTRACT We report the first characterization of the individual discs in the intermediate-separation binary systems KK Oph and HD 144668 at millimetre wavelengths. In both systems, the circumprimary and the circumsecondary discs are detected in the millimetre continuum emission, but not in 13CO nor C18O lines. Even though the disc structure is only marginally resolved, we find indications of large-scale asymmetries in the outer regions of the primary discs, most likely due to perturbation by the companion. The derived dust masses are firmly above debris disc level for all stars. The primaries have about three times more dust in their discs than the secondaries. In the case of HD 144668, the opacity spectral index of the primary and secondary differ by a large margin of 0.69, which may be a consequence of the secondary disc being more compact. Upper limits on the gas masses imply less than 0.1 Mjup in any of these discs, meaning that giant planets can no longer form in them. Considering that there have been no massive gas discs identified to date in intermediate-separation binaries (i.e. binaries at a few hundred au separation), this opens space for speculation whether their binarity causes the removal of gas, with tidal interaction truncating the discs and hence shortening the accretion time-scale. More systematic studies in this respect are sorely needed.</jats:p