Around 50 planetary nebulae (PNs) are presently known to possess ``small-scale'' low-ionization structures (LISs) located inside or outside their main nebular bodies. We consider here the different kinds of LISs (jets, jetlike systems, symmetrical and nonsymmetrical knots) and present a detailed comparison of the existing model predictions with the

EN ESTA TESIS PRESENTAMOS LA BUSQUEDA, DETECCION Y CARACTERIZACION DE LAS ENANAS MARRONES EN EL CUMULO ABIERTO JOVEN DE LAS PLEYADES. PARA ELLO HEMOS REALIZADO DOS EXPLORACIONES FOTOMETRICAS CCD EN LOS FILTROS RI E IZ QUE HAN CUBIERTO 0.16 GRADOS 2 Y 1 GRADO 2 EN EL CENTRO DEL CUMULO, Y ALCANZADO MAGNITUDES LIMITE I= 21.0 Y 22.2, RESPECTIVAMENTE

We evaluate the stratification of acoustic oscillations in the solar photosphere in both the Lagrangian (comoving) frame of reference and the Eulerian (inertial) frame of reference, from a temporal sequence of model atmospheres in an optical depth scale obtained after a quasi-non-LTE inversion of the radiative transfer equation applied to spectral

The turbulent convection zone is now considered as the only known source of the excitation of p-modes in the Sun. In Perez and Roca Cortes (1999) an analysis was made of the data set available to date of GOLF aboard SOHO (before SOHO loss), checking that the energy distribution of the acoustic modes is of a Boltzmann type. At present we have a new

In helioseismic inversions, the number of independent pieces of information that a mode set contains is much less than the actual number of modes. This is due in part to the similarity between the basis functions that define the inverse problem, the kernels, while the observational errors also contribute to the loss of independent information. We

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