The (B0+?)+O6 system FN CMa: A case for tidal-pulsational interaction?

FN CMa is visually double with a separation of about 0.6arcsec. Sixty high-cadence VLT/UVES spectra permit the A and B components to be disentangled, as the relative contribution of each star to the total light entering the spectrograph fluctuates between exposures due to changes in seeing. Component A exhibits rapid line-profile variations, leading us to attribute the photometric variability seen by HIPPARCOS (with a derived P=0.08866d) to this component. From a total of 122 archival and new echelle spectra it is shown that component A is an SB1 binary with an orbital period of 117.55 days. The eccentricity of 0.6 may result in tidal modulation of the pulsation(s) of component Aa.Comment: 2 pages, 1 figure, IAUS 272 - Active OB Stars: Structure, Evolution, Mass Loss and Critical Limit

The magnetic field of zeta Orionis A

Zeta Ori A is a hot star claimed to host a weak magnetic field, but no clear magnetic detection was obtained so far. In addition, it was recently shown to be a binary system composed of a O9.5I supergiant and a B1IV star. We aim at verifying the presence of a magnetic field in zeta Ori A, identifying to which of the two binary components it belongs (or whether both stars are magnetic), and characterizing the field.Very high signal-to-noise spectropolarimetric data were obtained with Narval at the Bernard Lyot Telescope (TBL) in France. Archival HEROS, FEROS and UVES spectroscopic data were also used. The data were first disentangled to separate the two components. We then analyzed them with the Least-Squares Deconvolution (LSD) technique to extract the magnetic information. We confirm that zeta Ori A is magnetic. We find that the supergiant component zeta Ori Aa is the magnetic component: Zeeman signatures are observed and rotational modulation of the longitudinal magnetic field is clearly detected with a period of 6.829 d. This is the only magnetic O supergiant known as of today. With an oblique dipole field model of the Stokes V profiles, we show that the polar field strength is ~ 140 G. Because the magnetic field is weak and the stellar wind is strong, zeta Ori Aa does not host a centrifugally supported magnetosphere. It may host a dynamical magnetosphere. Its companion zeta Ori Ab does not show any magnetic signature, with an upper limit on the undetected field of $\sim$ 300 G

Spatial distribution of stellar rotational axes from Be stars

Para conocer la distribución de velocidades de rotación de las estrellas Be, se utiliza la suposición estándar que los ejes de rotación se distribuyen uniformemente. En este trabajo usamos ángulos proyectados de polarimetría de casi 500 estrellas Be y realizamos un análisis estadístico. Además llevamos a cabo una simulación Monte Carlo cuyos resultados explican las características observadas de los ángulos, confirmando que provienen de una distribución uniforme, pero que sus ángulos proyectados poseen una estructura bimodal. Esta última característica podría cambiar las conclusiones acerca de la distribución de velocidades de rotación de estas estrellas.In order to know the distribution of rotational velocities of Be stars, a standard assumption is used, namely that the rotational axes are uniformed distributed. We use here polarimetric projected angles data from almost 500 Be stars and we make a statistical analysis. Furthermore we perform a Monte-Carlo simulation that explains the observed features of the angles, confirming that it is indeed uniform distributed, but the projected angles possess a bimodal structure. This last features may change the conclusion about the rotational velocity distribution of these stars.Fil: Curé, M.. Universidad de Valparaíso; ChileFil: Christen, A.. Universidad de Chile; ChileFil: Rivinius, Th.. European Southern Observatory; ChileFil: Rial, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Investigaciones Matemáticas "luis A. Santaló"; Argentina. Universidad de Valparaíso; Chil