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

Discrete events with internally consistent properties are found in the light curve of the active galaxy BL Lac, which are consistent with the expected properties of stellar disruptions in standard loss-cone models of quasar energy generation. The amplitude distribution of events resembles the local mass distribution. It is argued that stochastic

A new ionization correction factor (ICF) scheme for He(+) is developed, based on the definition of the radiation softness parameter eta (Vilchez and Pagel, 1988) which is very sensitive to the effective temperature of the ionizing star(s) and, therefore, a good indicator of the He(+)-He(0) ionization structure while remaining insensitive to other

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