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General properties of Luminous Blue Variables (LBV) have been reviewed by Lamers (1987). The LBV's are all close to the Humphreys-Davidson luminosity upper limit. The semi periods of the photometric microvariations with Delta V is about 0.1m are about twice as large as for normal supergiants of the same L and Teff, and 4-20 times larger than the

EN EL MARCO DE ESTA TESIS SE RESUELVE EL PROBLEMA DE DETERMINAR EL ESTADO DE EXCITACION O IONIZACION DE UNA ESPECIE QUIMICA DADA, CONSISTENTE CON EL CAMPO DE RADIACION GENERADO EN PLASMAS INHOMOGENEOS CON MODELOS ATOMICOS COMPLEJOS. EL PROBLEMA SE SOLUCIONA CON DOS METODOS DIFERENTES: ITERACION LAMBDA ACELERADA Y EL METODO DE LOS ATOMOS

The light curve of the outburst of Comet P/Metcalf-Brewington (1991 I) is investigated. The parameters of the light curve are quite uncertain as it may be fitted both in terms of variation with heliocentric distance and exponential decay with time however, after maximum a empirical fit of m1 = 4.1 + 5 log Delta + 14.8 log r gives a good fit to the

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We propose a new approach to minimize the instrumental polarization (IP) of current polarimetric observations. It is shown how the instrumental polarization can be deduced and removed, by using lines with no intrinsic linear polarization. Notably, no specific understanding of the polarizing properties of our optical setup is required. For the