This paper reports on extensive spectroscopic observations of the WR-ring nebulae NGC 2359 and RCW 78, respectively, excited by the WN5 stars HD 56925 and WN8 HD 117688. For the first object, abundances were determined for O/H, Ne/H, N/H, and He/H in many different positions, including the ionized gas in the bubble, inside the optical shell

Morphology and elliptically averaged luminosity profiles have been derived from CCD surface photometry of thirteen Seyfert galaxies. Apparent V and I magnitudes, V - I color index, as well as absolute Mv and MI magnitudes have been calculated. V and I luminosity profiles of Mk 10, Mk 79, Mk 358, Mk 618, Mk 352, and Mk 110, are adjusted by the usual

This paper presents observations of the 3130 A Be II resonance doublet in stars of intermediate metal deficiency, with Fe/H values between -0.6 and -1.1, obtained with the Intermediate Dispersion Spectrographs and IPCS detector at the 2.5 m Isaac Newton Telescope on La Palma. The derived beryllium abundances range from 5.6 x 10 to the -12th (one

A cyclical approximation of the evolutionary synthesis of stellar populations has been developed into a general solution for the mass and time-dependence of the 'birth function' of stars. The general solution allows introduction of a function, G(t), which is the ratio of gas injected into a defined region to that which form stars in the same time

Via optical low-resolution long slit spectroscopy conducted at the 2.5 m INT in La Palma, He, O, N, Ne, A, and S abundances in 13 extended PN were calculated. The analysis of these results made it possible to infer that the nitrogen and oxygen abundances do not correlate, which implies that probably not all the nitrogen found was produced in the

This paper presents a self-consistent method to determine abundance and evolutionary status for giant H II regions (GHR) as well as the nominal temperature of the ionizing cluster and the ionization parameter. This new method makes it possible to recalibrate the empirical relationship (R23, O/H) by Pagel et al (1979) up to abundances three times