In addition to the large-scale outflows, which form their round, elliptical, and bipolar shells, planetary nebulae (PNe) also have, usually on smaller scales, pairs of highly collimated outflows, or jets. These jets, as well as the pairs of knots that appear at their tips (very prominent in the low-ionization emission lines), are the subject of the

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I review our knowledge about effective temperatures and masses of massive OB stars paying special attention to results recently obtained using new atmospheric models including sphericity, mass-loss and line-blanketing. The new temperature scales for O dwarfs and supergiants are lower than previously accepted. No systematic mass discrepancy is found

From inversion of a time series of slit spectra, observed in a quiet region of the solar photosphere, averaged models of a granular cell have been obtained showing the stratification of physical quantities versus optical depth and geometrical height. Furthermore a semi-empiric dynamic model of a mean granular cell has been derived and the results

Preliminary results of a candidate luminous blue variable (LBV) search made in a region of M33 are presented. The objects were found with narrow band filter images centered on characteristic emission lines of these objects. We show that the GTC, with the appropriate instrumentation, would generate important results through the analysis of high

A time series of broadband images of a sunspot near the disk center was obtained simultaneously in two wavelength bands at 0.56 mu m and 1.55 mu m at the German VTT on June 17, 1998. We computed intensity difference images of the best frame pairs which reveal information about the facular distribution in the present field of view. Faculae are found