Context: Models of flux emergence frequently use a twisted cylindrical loop as the initial starting configuration and ignore the coupling between the radiation field and plasma. In these models, the axis of the original tube never emerges through the photosphere. Without the axis emerging, it is very difficult to form a realistic sunspot. Aims: The

One of the main problems facing development teams working on instrument control systems consists on the need to access mechanisms which are not available until well into the integration phase. The need to work with real hardware creates additional problems like, among others: certain faults cannot be tested due to the possibility of hardware damage

We have calibrated the effective temperatures of the low main sequence stars ranging spectral types from F0 to K5 versus [Fe/H] and colours (B-V), (R-I), (V-R), (V-I), (V-K), (J-H), (J-K) and ubvy-β, using a large sample of dwarfs and subdwarfs. The effective temperatures, scaled to direct T_eff_ determinations via reliable angular diameter

Several aspects of the evolution of an SNR into a low-beta ISM are investigated. The presence of a strong magnetic field in the unperturbed ISM is found to have a profound effect on the structure and evolutionary pattern of an SNR embedded in it. If the field strength is high enough for the outgoing shock to be weak, then most of the explosion

The authors have made observations of the spectrum of comet Halley on various dates between September 1985 and December 1986, obtaining multipositional long-slit absolute spectrophotometry of the inner region of the coma in the visible range. They present a study of the emission in the 3883 Å line of the (0-0) transition of CN. The observed CN

Delta Scuti (δSct) stars are opacity-driven pulsators with masses of 1.5-2.5Msolar, their pulsations resulting from the varying ionization of helium. In less massive stars such as the Sun, convection transports mass and energy through the outer 30per cent of the star and excites a rich spectrum of resonant acoustic modes. Based on the solar example