We obtain the RPA summed one-meson exchange potential between nucleons in symmetric nuclear matter at zero temperature, from a model which includes $ ho $, $sigma $, $omega $ and $pi $ mesons. The behavior of rho mesons inside the medium is first discussed using different schemes to extract a finite contribution from the vacuum polarization. These

The major purpose of this paper is to investigate the nature of planetary nebulae (PNe) candidates in the southern hemisphere, taken from an internal list. We present spectroscopic observations and imaging of six PNe identified for the first time. Another candidate turned out to be a galaxy. All observed PNe represent evolved stages, their angular

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We present the results of a three-year campaign of broad-band photometry in the near-infrared J, H, K and L' bands for a sample of approximately 250 giant stars carried out at the Observatorio del Teide (Tenerife, Spain). Transformations of the Telescopio Carlos Sanchez system into/from several currently used infrared systems are extended to the

We report Hubble Space Telescope NICMOS observations of the central region of NGC 5128 at 2.2 mu m and in Pa alpha . The continuum images show extended emission typical of an elliptical galaxy and a strong unresolved central source we identify as the nucleus of the galaxy. Its position is consistent with ground-based IR and radio data, and with the

An excellent series of images of solar granulation was taken during the partial solar eclipse of 1994 May 10 at the Swedish Vacuum Solar Telescope at Roque de los Muchachos Observatory. Making use of the lunar limb profile, images at different heliocentric positions were corrected for instrumental and atmospheric effects. The centre-to-limb