ELMER is an instrument for the GTC designed to observe between 365 and 1000 nm. The observing modes for the instrument at Day One shall be: Imaging, Long Slit and Mask-Multi-object Spectroscopy, Slit-less multi-object spectroscopy, Fast Photometry and Fast short-slit spectroscopy, over a FOV of 4.2 arcmin diameter. Spectral resolutions of 250, 1000

We investigate the formation of polarization profiles induced by a magnetic field in the He I multiplet at 10830 Å. Our analysis considers the Zeeman splitting in the incomplete Paschen-Back regime. The effects turn out to be important and produce measurable signatures on the profiles, even for fields significantly weaker than the level-crossing

The accepted explanation of the observed dichotomy of two orders of magnitude between in situ measurements of electron density in H II regions, derived from emission line ratios, and average measurements based on integrated emission measure, is the inhomogeneity of the ionized medium. This is expressed as a ``filling factor", the volume ratio of

The prompt information given by the GRB Coordinates Network (GCN) differs very much for different GRBs. We compare the optical magnitudes quoted in GCNs for some recent events. Our compilation might help in planning coordinated observations in the future.

We have carried out multi-epoch, time-series differential I-band photometry of a large sample of objects in the south-east region of the young (˜3 Myr), nearby (˜350 pc) σ Orionis open cluster. A field of ˜1000 arcmin2 was monitored during four nights over a period of two years. Using this dataset, we have studied the photometric variability of

Four years after its announcement at SPIE, FLAMES, the VLT fibre facility, has been completed, integrated into the VLT observatory and commissioned. It has been in operation since February 2003. More than 250000 scientific (single) spectra have been obtained, which have enabled the on-sky performance of the instrument to be compared to the