The kinematics of Planetary Nebulae are analyzed in terms of the solutions to the equations of hydrodynamic equilibrium developed by J. Canto. We apply our analysis to the Planetary Nebulae NGC 6905 and NGC 6537. A detailed spectroscopic study of these objects reveals the existence of high nuclear velocities, together with complex kinematic

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The solar p-mode spectrum of very low l is measured with high accuracy for a long enough period of time so as to allow the search for solar cycle variations. In this paper solar cycle variations of the frequency and energy of the modes are confirmed. Moreover, a slight variation, within errors, of its rotational splitting with the solar cycle, is

The evolutionary scenario concerning the production and the cooling of He white dwarfs is revisited and discussed. We show that, for a given star metallicity, the minimum mass of H-rich envelopes able to support a red giant structure linearly decreases when the logarithm of the red giant luminosity increases. Increasing the metallicity the mass of

Sine 1984, simultaneous observations of irradiance and velocity solar acoustic modes, have been carried out by several authors in order to measure the phase difference between irradiance and velocity modes. Following the earliest observations with a stratospheric balloon (Frolich and van Der Raay, 1984), a two ground-based stations (Tenerife and

In the (logR_e_, μ_e_) plane defined by the logarithm of the effective radius and the effective surface brightness, elliptical galaxies that are members of Hickson's compact groups turn out to belong to the bright family, thus suggesting that most of them have likely experiences subtantial secondary evolution.