We present I-band photometry of the soft X-ray transient (SXT) J0422+32 taken during a low-brightness state over two weeks in 1993 October. The object had a mean V magnitude of 19.9, approximately 2mag above its subsequent, presumably quiescent, level of V~22.4. These data revealed a periodicity at 16.18h (significance level>99 per cent), but we

ESTA TESIS DOCTORAL CONTIENE LOS RESULTADOS DE UN PROGRAMA DE INVESTIGACION EN EL QUE SE HAN DETERMINADO EMPIRICAMENTE LAS RELACIONES TEMPERATURA EFECTIVA-COLOR-METALICIDAD PARA ESTRELLAS DE SECUENCIA PRINCIPAL CON TIPOS ESPECTRALES COMPRENDIDOS EN EL RANGO F0-K5. PARA LLEVAR A CABO ESTA CALIBRACION HA SIDO NECESARIO DESARROLLAR UNA SERIE DE

The amplitude of the gravitational waves emitted by a binary system of arbitrary eccentricity and orientation is developed in Fourier-Bessel series. Periastron advance is also considered. We discuss the influence of the orbital parameters in the spectrum of the wave amplitude. The dominant harmonic in the spectra gives a good estimation of the

We have investigated in detail the uncertainties in deriving beryllium abundances for metal-poor stars from the BeII resonance doublet at λ 3131A. These uncertainties are related to the quality of the observations, the physical data used, and the adopted stellar parameters. We have taken into account the NLTE effects on the lines formation for the

We present a spectroscopic analysis of the O9.7 Iab star HDE 226868, which is the optical counterpart of Cygnus X-1. We use this extreme supergiant to test the differences in the stellar parameters derived using plane parallel hydrostatic model atmospheres and spherical non-hydrostatic models ("Unified Model"). We find that the difference is

In the framework of the morphological survey of northern sky planetary nebulae, in progress at the IAC we investigate in detail those nebulae that show peculiarities or that have not been studied before. By means of narrowband imaging and accurate two-dimensional spectroscopy we analyzed the peculiar nebula M1-75. Its morphology is very complex