We present here preliminary results of our program to obtain rough abundance estimates for > 104 red giant branch and red clump stars in four fields of the LMC. The derived abundance distributions will be a strong constraint on models of the LMC's star-formation history based on field star color-magnitude diagrams.

We have investigated the possibility that radiation pressure might trigger planetary nebula (PN) ejection during helium-shell flashes in asymptotic-giant-branch (AGB) stars. We find that the outward flux at the base of the hydrogen envelope during a flash will reach the Eddington limit when the envelope mass Menv falls below a critical value that depends on the core mass MH and composition. These results may help to explain the helium-burning PN nuclei found in the Magellanic Clouds.

We address the question of reproducing the observed luminosity functions of carbon stars (CSLF) in both the LMC and SMC, characterized by quite different features (i.e., faint end and peak location), using a new formalism for the third dredge-up in TP-AGB models.

We have developed a population synthesis code, aimed mainly at the interpretation of CMDs. Magellanic Cloud clusters have been largely used for the test/calibration of the underlying stellar tracks.

With the detection of strong PAH features and H2 emission in selected knots of the N159, N11A, and 30 Dor regions in the LMC, we present the first results of a study that is part of a coordinated Guaranteed Time ISO programme to investigate star formation in the Magellanic Clouds. The PAH features have different ratios than the ones in Galactic reflection nebulae.

The initial/final mass relation (Mi–Mf) for small and intermediate mass stars depends strongly on the initial chemical composition (Z). Two factors play an important role in this effect: the dependence on Z of mass loss rates and the carbon-oxygen core initial mass. For heavy element abundances Z = 0.001 and Z = 0.02 the greatest differences of Mf and Mi are found between 1.5 < Mi/M⊙ < 4 and may be as great as 0.1 M⊙.

The presence of the carbon stars in the MC with luminosities higher or lower than predicted for thermally-pulsing (TP) AGB stars, can be explained by processes that happen during the early AGB (E–AGB) stage. I examine this assumption by means of a population simulation technique. I find that there must be TP–AGB C and S stars in the MC that formed as a result of mass transfer in binary systems. Their presence may influence the age determinations of MC clusters.

Certain aspects of the AGB population, such as the relative number of M and N stars, the mass loss rates, and the initial masses of carbon-oxygen cores, depend on the initial heavy element abundance Z. I have calculated synthetic populations of AGB stars for different initial Z values taking into consideration the evolution of single and close binary stars. I present the results of population syntheses of AGB stars in clusters as a function of different initial chemical compositions. The relation for the tip luminosity of AGB stars versus cluster age as a function of Z is presented and is used to determine the ages for a number of clusters in the LMC and the SMC, including clusters with no previous age determinations.

We present infrared photometry of LMC stars taken from a region of 2.5° in right ascension from the DeNIS (Deep Near Infrared Southern Sky Survey) survey.

I present results from an ongoing study of the evolution and mass loss of AGB stars with optically thick circumstellar envelopes in the Magellanic Clouds.

Accurate radial velocities have been obtained with the CORAVEL photoelectric scanner at ESO, La Silla, for 36 F-M supergiants in the 30 Dor and Shapley II regions of the LMC (5h20m < RA(2000) < 5h50m, −70°09′ < Dec (2000) < −68°30′). On the basis of these data, we revisit the content and spatial extent of the four kinematical groups of F-M supergiants discovered in this area by Prévot et al. 1989. Each is the oldest part of a larger star forming region, recognized by young HII regions or CO clouds, and/or a surrounding Hα + [NII] superbubble. We discuss various gas tracers including the interstellar sodium and calcium lines.

In the past 10 years, 6 classical novae have been observed in the Large Magellanic Cloud (LMC). We have begun a study of these objects using ultraviolet spectra obtained by IUE and optical spectra from nova surveys. We are using the results of this study to further our understanding of novae and stellar evolution.

Our study includes analysis of both the early, optically thick spectra using model atmospheres (Hauschildt et al. 1992), and the later nebular spectra using optimization of photoionization codes (Ferland 1996; James & Roos 1993). By analysing all the LMC novae in a consistent manner, we can compare their individual results and use their combined properties to calibrate Galactic novae. In addition, our studies can be used to determine the elemental abundances of the nova ejecta, the amount of mass ejected, and the contribution of novae to the ISM abundances. To date we have analysed Nova LMC 1988#1 (Schwarz et al. 1998) and Nova LMC 1990#1 (Vanlandingham et al. 1999), and have obtained preliminary results for Nova LMC 1991. The results of this work are presented in this poster.

We observed a sample of zero proper-motion stars (μ < 0.″50 cent−1) from a field previously studied by Suntzeff et al. (1986). This field is 2°.5 NW (2.6 kpc) of the center of the SMC. We obtained spectra for ~ 40 stars in the region of the Ca II infrared triplet using the CTIO Argus fiber-fed spectrograph. We also obtained Argus echelle spectra of a single order at 6300Å with R = 18000 in one run. The low-dispersion spectra were reduced to metallicities based on the Ca II equivalent widths using the Da Costa & Armandroff (1995) technique and the metallicity scale from Zinn & West (1984). The typical abundance error is 0.12 dex. For half the sample, we have echelle velocities which are accurate to 1.5 km s−1. For the rest of the sample, the low-dispersion data yield single-observation velocities accurate to about 5 km s−1 based on repeat observations.

Recent results for the old and intermediate-age star clusters of the Magellanic Clouds are reviewed. Highlights include new evidence that the LMC old clusters are as old the Galaxy's halo globular clusters and the persistence of the LMC cluster “Age Gap” despite field star evidence for significant star formation during the cluster age gap epoch. For the SMC new data confirm the lack of significant change in cluster abundances with age prior to ~4 Gyr ago.

We report preliminary results from an automated cluster survey of the Magellanic Clouds aimed at improving the cluster census and at deriving cluster properties from their resolved stellar content. The survey is tripling the number of known clusters. The cluster age distribution shows similar peaks at 100–200 Myr in LMC and SMC, coincident with the closest encounter of the Clouds and perigalacticon.

The stellar associations are defined as loose unbound concentrations of young stars with a bright OB stellar component, mainly located at the most recent star forming regions, representing the smallest units in the hierarchy of stellar systems in galaxies. The definition of the associations is discussed and the main properties of their stellar content are summarized. Using plates taken with the 1.2m UK Schmidt Telescope a method is developed to detect all stellar associations in the LMC and to find their spatial distribution relative to the LMC's recent star formation history. In 40% of the LMC region, the number of “single peak” associations has increased considerably (~ 3x). A very interesting result is that the faint limit, where the identified associations are revealed, varies by about 3 mag. This indicates not only extinction differences but also the presence of pre-main sequence stars at a wide range of masses.

We present deep luminosity functions derived from HST STIS data for three rich LMC clusters (NGC 1805, NGC 1868, and NGC 2209), and for one Galactic globular cluster (NGC 6553). All of the LMC cluster luminosity functions are roughly consistent with a Salpeter IMF or with the solar neighbourhood IMF from Kroupa, Tout & Gilmore (1993). They continue to rise at least to 0.7M⊙. NGC 1868 shows evidence for mass segregation which may be primordial. A comparison of deep luminsoisty functions for seven Galactic globulars shows that the luminosity functions are eroded at low masses by amounts that are strongly correlated with distance from the Galactic plane.

Spontaneous and triggered star formation in the LMC is discussed with data on star clusters ages and positions. The supershell LMC4 and the stellar arcs in the same region are suggested to be triggered by GRBs, the progenitors of which might have escaped the old elliptical cluster NGC1978, close to which are a number of X-ray binaries and the SGR/SNR N49.

We report on a survey of 25 candidate old LMC clusters. Washington photometry was obtained on the CTIO 0.9m in < 1h, reaching below the turnoff. Ages based on the magnitude difference δT1 between the giant branch clump and the turnoff revealed that no new old clusters were found. The candidates all turned out to be of intermediate age (1–3 Gyr). We confirm that there was apparently no cluster formation in the LMC from 3–9 Gyr ago, and that there was a pronounced epoch of cluster formation beginning 3 Gyrs ago that peaked at ~1.5 Gyrs ago. We also determine ages for the surrounding fields, as well as metallicities for both the clusters and fields from the color of the giant branch. In most cases the stellar population of each cluster is quite similar to that of its field. The mean metallicity for the intermediate age outer disk clusters is −0.65. A few clusters stand out in the age-metallicity relation in the sense that they are intermediate age clusters at relatively low metallicity. In the northern part of the LMC disk 3 fields all have a secondary clump ~0.45 mag fainter than the dominant clump, suggesting a component located behind the LMC at a distance comparable to that of the SMC.

The LMC cluster NGC 1978 shows different properties in the two parts divided by its minor axis. These two parts have different color distributions of the core He-burning (CHB) stars and giant branch (GB) positions on the CMDs at and below the level of the CHB stars. These differences may be caused by spread in metallicity.