We review here the multiplicity properties of ultracool dwarfs (spectral type later than M6) observed in three different environments and at three different...
Ultracool Dwarf Science from Widefield Multi-Epoch Surveys
Widefield surveys have always provided a rich hunting ground for the coolest stars and brown dwarfs. The single epoch surveys at the beginning of this century...
Ultracool dwarfs in open clusters and star-forming regions
In this contribution I review the results of the UKIRT Infrared Deep Sky Survey (UKIDSS) Galactic Clusters Survey (GCS) on the Initial Mass Function (IMF) and...
Ultracool dwarfs with spectral type M7 and later include very low-mass stars as well as brown dwarfs. Due to their intrinsic faintness, only 9 very low-mass...
Ultracool Dwarfs in the Ukirt Infrared Deep Sky Survey (UKIDSS)
The UKIRT Infrared Deep Sky Survey (UKIDSS) Large Area Survey (LAS) presents an unparallelled resource for the study of field brown dwarfs. The UKIDSS Cool...
Ultracool Subdwarfs: The Halo Population Down to the Substellar Limit
Ultracool subdwarfs are low luminosity, late-type M and L dwarfs that exhibit spectroscopic indications of subsolar metallicity and halo kinematics. Their...
Ultraluminous X-ray Sources: Beambags and Optical Counterparts
A significant fraction of ultraluminous X-ray sources appear to be embedded in observable ionized nebulæ that take the form of large, several 100 pc diameter...
Ultraluminous X-ray Sources: Bubbles and Optical Counterparts
Optical studies of ultraluminous X-ray sources (ULX) in nearby galaxies have turned out to be instrumental in discriminating between various models including...