LA TESIS PRESENTADA EXPONE UN NUEVO METODO PARA DERIVAR LA HISTORIA DE LA FORMACION ESTELAR EN GALAXIAS IRREGULARES ENANAS. INTENTOS ANTERIORES SE HAN VISTO SIEMPRE MUY LIMITADOS DEBIDOS A LA DIFICULTAD DE SEPARAR LOS EFECTOS DE LA EDAD Y LA METALICIDAD DE LAS ESTRELLAS, JUNTO CON LAS INCERTIDUMBRES EN DIFERENTES PARAMETROS (EL RITMO DE FORMACION

We discuss in detail the evolutionary path of the multiple-shell planetary nebula M1-46, in the light of our new observations. The velocities of the halo and main nebula correspond to a dynamical time lap between the shells of about 6.8 x 104 yr. By means of a non-LTE analysis of the central star's spectrum, we derived a stellar temperature of Teff

The Sun is not a rigid body and it is well known that its surface rotation is differential, the polar regions rotating substantially slower than the equator. This differential rotation has been demonstrated by helioseismology to continue down to the base of the convective zone, below which it becomes closer to a rigid body rotation. Far deeper

LA TESIS PRESENTADA COMBINA ECUACIONES DE FOTOIONIZACION E HIDRODINAMICOS PARA DETERMINAR LA ESTRUCTURA DE NEBULOSAS IONIZADAS. EL CODIGO INCLUYE LA DEPENDENCIA TEMPORAL DE DICHAS ECUACIONES, CON LO QUE ES POSIBLE ESTUDIAR LA EVOLUCION DE LA NEBULOSA. EL TRABAJO INCLUYE COMPARACIONES CON RESULTADOS PREVIOS HASTA DONDE ES POSIBLE, LO QUE PERMITE

We have applied the InfraRed Flux Method (IRFM) to a sample of 475 dwarfs and subdwarfs in order to derive their effective temperatures with a mean accuracy of about 1.5%. We have used the new homogeneous grid of theoretical model atmosphere flux distributions developed by Kurucz (1991, 1993) for the application of the IRFM. The atmospheric

Bidimensional spectroscopy of the circumnuclear region (central 10" x 8") of the Seyfert 2 galaxy NGC 1068 has been performed by means of an optical fiber system. The 95 spectra obtained simultaneously include the [N II] λλ6548, 6583, Hα, and [S II] λλ6716,6731 emission lines. In the inner regions, the velocity field obtained by cross-correlating