As part of a systematic effort to characterize the properties and progenitors of the most luminous planetary nebulae (PNe), we obtained a sample among the brightest PNe in two stellar systems of different metallicities: LMC (Z/Z⊙~0.5) and M31 (Z/Z⊙~1) by means of a combined effort with the VLT and the 10mGTC. Modelling of these data will allow us to infer the masses of the stellar progenitors, gaining insights into the controversial origin of the universal cutoff of the Planetary Nebulae Luminosity Function (PNLF).

We are preparing a catalog of extragalactic planetary nebulae. The current number of entries is $\sim$8,000 objects, with the largest samples coming from the Local Group (SMC, LMC, M33, and M31), but with representation from over 55 galaxies. The catalog is expected to be complete in late 2007.

The bright star Sk—67°18 (Brey 5) in the Large Magellanic Cloud (LMC) contains an eclipsing binary system. Our radial velocity study reveals that the orbital period is almost exactly two days. The spectra also show that the star's primary component is not of spectral type WN, but that the star is rather an Of+O type binary where the primary is probably of type O3f*. Furthermore, Sk—67°18 appears to be a high-mass multiple system.

We present the results of a multifrequency observation of the WO star Sand 2 in the LMC. Two ROSAT PSPC observations, with exposure times of 8953 s and 4540 s, are used to investigate possible X-ray emission from Sand 2. The optical spectrum observed with the ESO 2.2m telescope close to the time of the ROSAT observations, shows strong emission lines of HeII, CIV, OV and OVI. All lines have a velocity broadening of 4 200±100 km s−1. The UV spectrum from the IUE archive shows a CIV resonance doublet at 155 nm with a P-Cygni absorption at ∼ −5 000 km s−1, with wings extending to about −8 000 km s−1. A combination of two different BB temperatures (80 000 K and 25 000 K) are required to fit the UV-optical continuum, dereddened by EB-V = 0.25.