Related papers: On the Formation of Brown Dwarfs
Observations of accretion disks around young brown dwarfs have led to the speculation that they may form planetary systems similar to normal stars. While there have been several detections of planetary-mass objects around brown dwarfs…
The typical product of the star formation process is a binary star. Binaries have provided the first dynamical measures of the masses of pre-main-sequence (PMS) stars, providing support for the calibrations of PMS evolutionary tracks.…
A long standing and unverified prediction of binary star evolution theory is the existence of a population of white dwarfs accreting from sub-stellar donor stars. Such systems ought to be common, but the difficulty of finding them, combined…
Observations of brown dwarfs provide important feedback on theories of atmospheres and inner structure of substellar objects. Brown dwarf binary systems furthermore offer the unique opportunity to determine the mass of individual brown…
In the initial formation stages young stars must acquire a significant fraction of their mass by accretion from a circumstellar disk that forms in the center of a collapsing protostellar cloud. Throughout this period mass accretion rates…
When a star exhausts its nuclear fuel, it either explodes as a supernova or more quiescently becomes a white dwarf, an object about half the mass of our Sun with a radius of about that of the Earth. About one fifth of white dwarfs exhibit…
Brown dwarfs are intermediate objects between planets and stars. The lower end of the brown-dwarf mass range overlaps with the one of massive planets and therefore the distinction between planets and brown-dwarf companions may require to…
Precise measurements of the fundamental properties of low-mass stars and brown dwarfs are key to understanding the physics underlying their formation and evolution. While there has been great progress over the last decade in studying the…
Properties of nearby dwarf galaxies are briefly discussed. Dwarf galaxies vary widely in their star formation histories, the ages of their subpopulations, and in their enrichment history. Furthermore, many dwarf galaxies show evidence for…
The formation of planets is one of the major unsolved problems in modern astrophysics. Planets are believed to form out of the material in circumstellar disks known to exist around young stars, and which are a by-product of the star…
Since their initial discovery, the origin of isolated white dwarfs (WDs) with magnetic fields in excess of $\sim$1 MG has remained a mystery. Recently, the formation of these high-field magnetic WDs has been observationally linked to strong…
We have performed a survey for substellar companions to young brown dwarfs in the Taurus star-forming region using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope. In these data, we have discovered a candidate…
We have imaged two bona-fide brown dwarfs with TReCS/GEMINI-S and find mid-infrared excess emission that can be explained by optically thick dust disk models. In the case of the young ($\approx$2Myr) Cha H$\alpha$1 we measure fluxes at…
The slow rotation of some young stars and the extreme rotation periods of some Ap stars have so far defied explanation. The absence of sufficiently efficient braking mechanisms for newly formed stars points to the star formation process…
Stars in globular clusters formed and evolved in the most extreme environment: high density and low metallicity. If the formation of stars and planets are at all sensitive to environmental conditions, this should therefore be evident in…
Abridged/ We present numerical results on the properties of young binary and multiple stellar systems. Our analysis is based on a series of SPH + Nbody simulations of the fragmentation of small molecular clouds, that fully resolve the…
We explore two ways in which objects of planetary masses can form. One is in disk systems like the solar system. The other is in dense clusters where stars and brown dwarfs form. We do not yet have the instrumental accuracy to detect…
Young stars form on a wide range of scales, producing aggregates and clusters with various degrees of gravitational self-binding. The loose aggregates have a hierarchical structure in both space and time that resembles interstellar…
We present evidence which indicates the luminosity functions of star forming regions, open star clusters and the field dips between spectral types M7-M8. We attribute this to a sharp local drop in the luminosity-mass relation and speculate…
I review some recent work on low-mass star formation, with an emphasis on theory, basic principles, and unresolved questions. Star formation is both a gravitational fragmentation problem as well as an accretion problem. Molecular cloud…