We present imaging and spectroscopic observations with HST (WFPC2, ACS/HRC and STIS), VLT (FORS2) and Keck (HIRES) of the dM 8 ultra-cool dwarf DENIS-P J185950.9-370632, located in the R-CrA region. The presence of lithium absorption at 670.8 nm and the strong Hα emission indicate a young age and a sub-stellar mass. Our diffraction-limited images

The three images in fits format correspond to the flux map, coverage map and signal-to-noise ratio map of the mosaic combining all the images taken in the survey. The two tables contain the list of objects detected in the mosaic. Table 3 contains the list of highly reliable detections. Only a few false detections are expected in this list. Table 4

Thick disks are faint and extended stellar components found around several disk galaxies including our Milky Way. The Milky Way thick disk, the only one studied in detail, contains mostly old disk stars (≈10 Gyr), so that thick disks are likely to trace the early stages of disk evolution. Previous detections of thick disk stellar light in external

We present relations between thermal and magnetic quantities in a simple, isolated sunspot, as deduced from the inversion of 1.56 μm spectropolarimetric data. We used a combination of two infrared Fe I lines at 15 648.5 Å and 15 652.8 Å/ in the inversions. Due to the high Zeeman sensitivity of these lines, we can study this relationship in the

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We review different surveys, in the optical and infrared, conducted in the very young (age 1 8 Myr), nearby (d ˜ 350 pc) σ Orionis cluster aimed to characterize the substellar population. We describe spectral characteristics of very low mass stars, brown dwarfs and planetary mass objects in the cluster with spectral types from K7 to T6. We study