A cyclic bipolar wind in the interacting binary V 393 Scorpii

V393 Scorpii is a double periodic variable characterized by a relatively stable non-orbital photometric cycle of 253 d. Mennickent et al. argue for the presence of a massive optically thick disc around the more massive B-type component and describe the evolutionary stage of the system. In this paper, we analyse the behaviour of the main spectroscopic optical lines during the long non-orbital photometric cycle. We study the radial velocity of the donor determining its orbital elements and find a small but significant orbital eccentricity (e = 0.04). The donor spectral features are modelled and removed from the spectrum at every observing epoch using the light-curve model given by Mennickent et al. We find that the line emission is larger during eclipses and mostly comes from a bipolar wind. We also find that the long cycle is explained in terms of a modulation of the wind strength; the wind has a larger line and continuum emissivity at the high state. We report the discovery of highly variable chromospheric emission in the donor, as revealed by the Doppler maps of the emission lines Mg II 4481 and C I 6588. We discuss notable and some novel spectroscopic features like discrete absorption components, especially visible at blue depressed O I 7773 absorption wings during the second half-cycle, Balmer double emission with V/R curves showing 'Z-type' and 'S-type' excursions around secondary and main eclipses, respectively, and H beta emission wings extending up to +/- 2000 km s(-1). We also discuss possible causes for these phenomena and for their modulations with the long cycle.

Alessi 95 and the short-period Cepheid SU Cassiopeiae

The parameters for the newly discovered open cluster Alessi 95 are established on the basis of available photometric and spectroscopic data, in conjunction with new observations. Colour excesses for spectroscopically observed B- and A-type stars near SU Cas follow a reddening relation described by E(U-B)/E(B-V) = 0.83 + 0.02E(B-V), implying a value of R=AV/E(B-V) ? 2.8 for the associated dust. Alessi 95 has a mean reddening of E(B-V)(B0) = 0.35 +/- 0.02 s.e., an intrinsic distance modulus of V0-MV= 8.16 +/- 0.04 s.e. (+/- 0.21 s.d.), d= 429 +/- 8 pc, and an estimated age of 108.2 yr from zero-age main sequence (ZAMS) fitting of available UBV, CCD BV, NOMAD, and Two Micron All Sky Survey JHKs observations of cluster stars. SU Cas is a likely cluster member, with an inferred space reddening of E(B-V) = 0.33 +/- 0.02 and a luminosity of < MV >=-3.15 +/- 0.07 s.e., consistent with overtone pulsation (PFM= 2.75 d), as also implied by the Cepheids light-curve parameters, rate of period increase and Hipparcos parallaxes for cluster stars. There is excellent agreement of the distance estimates for SU Cas inferred from cluster ZAMS fitting, its pulsation parallax derived from the infrared surface brightness technique and Hipparcos parallaxes, which all agree to within a few per cent.

OXYGEN ABUNDANCES IN LOW- AND HIGH-alpha FIELD HALO STARS AND THE DISCOVERY OF TWO FIELD STARS BORN IN GLOBULAR CLUSTERS

Oxygen abundances of 67 dwarf stars in the metallicity range -1.6 < [Fe/H] < -0.4 are derived from a non-LTE analysis of the 777 nm O I triplet lines. These stars have precise atmospheric parameters measured by Nissen and Schuster, who find that they separate into three groups based on their kinematics and alpha-element (Mg, Si, Ca, Ti) abundances: thick disk, high-alpha halo, and low-alpha halo. We find the oxygen abundance trends of thick-disk and high-alpha halo stars very similar. The low-alpha stars show a larger star-to-star scatter in [O/Fe] at a given [Fe/H] and have systematically lower oxygen abundances compared to the other two groups. Thus, we find the behavior of oxygen abundances in these groups of stars similar to that of the a elements. We use previously published oxygen abundance data of disk and very metal-poor halo stars to present an overall view (-2.3 < [Fe/H] < +0.3) of oxygen abundance trends of stars in the solar neighborhood. Two field halo dwarf stars stand out in their O and Na abundances. Both G53-41 and G150-40 have very low oxygen and very high sodium abundances, which are key signatures of the abundance anomalies observed in globular cluster (GC) stars. Therefore, they are likely field halo stars born in GCs. If true, we estimate that at least 3% +/- 2% of the local field metal-poor star population was born in GCs.

Evaluación de la sustentabilidad en la instalación de plantas desaladoras, de agua de mar, en la región noroeste de México

Programa de doctorado en Ingenierí­a Ambiental y Desalinización

Convertidor de potencia con almacenamiento energético, para la interconexión de sistemas eléctricos de reducida potencia

Programa de Doctorado: Ingenierí­a Ambiental y Desalinización

Estudio de sistemas de limpieza en membranas de ósmosis inversa

Programa de Doctorado en Gestión y Tratamiento de Residuos Tóxicos y Peligrosos

Mejora del Compilador/Generador de Esqueletos C++ para Componentes CoolBOT

Máster Universitario en Sistemas Inteligentes y Aplicaciones Numéricas en Ingeniería (SIANI)