We show that a certain amount of non-local overshoot at the base of the outer convective envelop of low mass stars, while climbing along the RGB toward central He-ignition, explains the shift of about 0.4V mag required to bring the luminosity of the bump predicted in the theoretical RGB luminosity functions into agreement with the observational one.

We find that a certain amount of non-local overshoot at the base of the outer convective envelope affects the evolution of intermediate mass stars in the H-R diagram, producing extended loops even for models computed with significant overshoot from the central convective core, improving in this way upon a weak point of models with core overshoot.

Encouraged by a theoretical model we are monitoring supernova 1987A at 45 MHz in an attempt to detect its scintillation. So far the result is negative, but the program will continue.

Type II supernovae play a major role in the dynamics of the interstellar medium. The interstellar medium in which such supernovae evolve is often considerably modified by the strong stellar winds both from the progenitor and other nearby stars. The result is that the appearance and energetics of the remnants can be very different from that of remnants in a uniform medium. In this paper we will consider the evolution of supernova remnants in stellar wind bubbles including the effect of departures from spherical symmetry. The aim is to understand both the appearance of such remnants and their effect on the overall energetics of the interstellar medium.

We present the results of a spectroscopic study of planetary nebulae (PN) in the Magellanic Clouds. The optical survey of He, N, O, and Ne abundances by Monk et al. (1988) has been updated by higher S/N AAT optical data. In addition, carbon and other elemental abundances have been derived from the IUE spectra of 38 PN. Ionized nebular masses have been derived for 80 PN. The ionised mass versus nebular electron density plot shows that planetary nebulae become optically thin when their electron densities drop below 4500 cm--3. Below this density, the mean nebular hydrogen mass found for non-Type I PN is 0.22±0.08 M⊙. Using Zanstra and energy-balance methods, the mean central star mass found for 14 SMC and LMC PN is 0.59±0.02 M⊙.

An experimental survey of ultra-high-energy γ-ray sources in the Magellanic Clouds is described. Results of the survey may be used to study the intergalactic magnetic field.

Low resolution spectra from 1200 to 3300Å have been obtained, with the IUE satellite, for seven blue giants and supergiants in the young, metal-poor globular cluster NGC 330 in the Small Magellanic Cloud (SMC). A further three spectra from the IUE archive have been added to the sample, covering a range of 2.5 mag. The effective temperatures and the local reddening in the SMC have been estimated, and the star positions in the theoretical HR diagram determined, and compared with theoretical predictions for massive star evolution. Substantial discrepancies have been found.

We have obtained Washington CCD photometry with the CTIO 4m and 1.5m for ˜50 intermediate-to-old age star clusters in the Clouds. The data extend to near or below the main sequence and provide excellent photometry for the giants, from which precise (internal errors <0.1 dex) mean cluster abundances can be determined. We present data for several of the clusters and discuss the results. Intermediate resolution spectra have also been obtained for some 16 clusters with the CTIO 4m ARGUS multiple-object fibre-fed spectrograph. Finally, we have also obtained high dispersion (R˜20,000) échelle spectra for several of the brighter giants in a small sample of Large Magellanic Cloud (LMC) clusters. Detailed elemental abundances derived from these spectra will be presented. These data will help refine our knowledge of the age-metallicity relation in the Clouds.

The process of star formation (SF) and the modalities with which it occurs in galaxies of different sizes are still poorly understood. On the other hand, interpretation of the chemical and photometric properties of galaxies requires the adoption of adequate laws for the SF rate and Initial Mass Function (IMF) in model computations. Dwarf irregular galaxies in the Local Group offer the chance to study their SF history through analysis of their HR diagrams, which can be derived down to V 25, corresponding to MV0, i.e. to main sequence stars of 2 M⊙. Therefore, for these galaxies, we can derive information on the star formation activity which has occurred over the last 1 Gyr approximately. In this framework, we have undertaken CCD observations of Dwarf irregular galaxies in the Local Group with ESO telescopes and briefly present here the results obtained for DDO 210, Sextans B and NGC 3109.

Spectroscopic observations of SN 1987A in the LMC in July 1987 are presented. The appearance of SN 1987A's optical spectrum was dominated by strong H I and Na I lines showing broad P-Cygni profiles. The nebular emission lines of [O I] 6300, 64 appeared in mid-July. The enhancement of s-processed elements of Ba II and Sr II in SN 1987A is briefly discussed.

We present the first high-resolution radio image of the supernova remnant N49 near the northern edge of the LMC. These observations with the Australia Telescope at 6cm wavelength (4 arcsec resolution) show a distinct radio shell. The shell structure of N49 is similar in radio and X-ray emission, with the maximum of the emission found in the southeastern part of the SNR.

The first high resolution radio image of the supernova remnant N132D shows a complex shell structure.

Over the last several years we have obtained photometric observations of the four suspected (W Men, HV 5637, HV 12671, HV 12842) R Coronae Borealis (RCB) stars in the Large Magellanic Cloud (LMC). Fourier analyses of the light curves has revealed some periodicity in HV 12842, where there appear to be at least two closely spaced periods of 55 and 60 d. High resolution spectra of HV 12842, obtained with the Ango-Australian Telescope (AAT), indicate that it has similar atmospheric properties to a number of warmer galactic RCB and hydrogen-deficient Carbon (HdC) stars, e.g. R CrB, RY Sgr and XX Cam.

We describe the preparation of charts and positions for 1035 cool red giant carbon stars discovered by the authors in the Large Magellanic Cloud (LMC). Not considered here are Small Magellanic Cloud (SMC) carbon stars, nor the M-type giants found in the LMC and SMC (Blanco et al. 1980, Blanco & McCarthy 1983). Charts of the C stars discovered are available in three formats: (a) 12 charts contain 186 C stars discovered in three central LMC regions (Blanco et al. 1980); (b) charts of C and late M stars in 52 LMC regions; these charts will not be published but are available from the authors (Blanco & McCarthy 1983, discussion); and (c) charts for 849 individual C stars in 49 regions of LMC (Blanco & McCarthy 1990).

A search for long period variables in the Small Magellanic Cloud (SMC) was made using I plates from the U.K. Schmidt telescope. Variables were identified using a blink comparator built specially for this project and plates were digitised to determine periods and light curves for suspected variables. Over 300 new variables with periods in excess of 100 days were found, some variables having periods in excess of 1000 days.

Lindsay 11 and NGC 1806 are globular clusters in the Small and Large Magellanic Clouds (SMC and LMC) respectively. Both clusters have extended asymptotic giant branches with carbon stars at the tip. Colour-magnitude diagrams are fitted with appropriate isochrones which indicate that both clusters belong to the abundant population of intermediate age in the Magellanic Clouds.

We have studied with the SEI method (Sobolev approximation plus Exact Integration of the transfer equation) seven hot stars, five belonging to the Large Magellanic Cloud (LMC) and two to the Small Magellanic Cloud (SMC), which have been observed with IUE in high resolution. We present preliminary results of the work, i.e. the terminal velocities and the optical depth of the P Cygni profile. An evaluation of qiM has been done, as well as a comparison with previous work.

Since the pioneering objective prism surveys by Westerlund (1960) and Blanco et al. (1980), the Magellanic Clouds have proved a fruitful site for exploring the evolution of AGB stars. We have used photometric techniques to extend the prism C-star surveys to M- and S-type AGB stars, constructing luminosity functions and obtaining spectra of individual stars for comparison with theoretical predictions. We have concentrated on the Large Magellanic Cloud (LMC), but we have recently obtained observations of luminous red giants in a region of the Small Magellanic Cloud (SMC). In this paper we compare the results from these studies of the two satellite systems.

In this paper we report preliminary results from a survey of RR Lyrae variable stars in the Large Magellanic Cloud.

The chemical and structural evolution of the Magellanic Clouds are compared with those of the Galaxy. Simple models with gas infall and bimodal star formation are assumed, and are constrained by the most recent observational data. The evolution of the gas content, and the He, C, O and Fe abundances are all successfully modelled. The abundance of N is, however, predicted too high, and the apparent ages of the oldest star clusters are inconsistent with the simple model.