Related papers: Angular momentum and disk evolution in very low ma…
Accretion disks in white dwarf systems are believed to be tilted. In a recent publication, the lift force has been suggested to be a source to disk tilt, a source that is likely relevant to all accretion disk systems. Lift is generated by…
We investigate isolated sub- and super-Chandrasekhar white dwarfs which lose angular momentum through magnetic dipole braking. We construct constant rest mass sequences by fulfilling all stability criteria of rotating configurations and…
We study the structure and evolution of the very early protostellar disk (``protodisk'') just after protostar formation, where disk self-gravity dominates and the stellar contribution is dynamically minor. The disk redistributes angular…
A variety of observations provide evidence for vigorous motion in the atmospheres of brown dwarfs and directly imaged giant planets. Motivated by these observations, we examine the dynamical regime of the circulation in the atmospheres and…
Disks around brown dwarfs (BDs) are excellent laboratories to study the first steps of planet formation in cold and low-mass disk conditions. The radial-drift velocities of dust particles in BD disks are higher than in disks around more…
Debris discs consist of belts of bodies ranging in size from dust grains to planetesimals; these belts are visible markers of planetary systems around other stars that can reveal the influence of extrasolar planets through their shape and…
We review five mechanisms for forming brown dwarfs: (i) turbulent fragmentation of molecular clouds, producing very low-mass prestellar cores by shock compression; (ii) collapse and fragmentation of more massive prestellar cores; (iii) disc…
Under the right conditions brown dwarfs that gain enough mass late in their lives to cross the hydrogen burning limit will not turn into low-mass stars, but rather remain essentially brown dwarf-like. While these objects, called either…
(Abridged) We have completed the first systematic survey for disks around spectroscopically identified young brown dwarfs and very low mass stars. We have obtained L'-band (3.8 um) imaging for 38 very cool objects in IC 348 and Taurus. Our…
Rapidly rotating late M dwarfs are observed in two different branches of magnetic activity, although they operate in the same stellar parameter range. Current empirical evidence indicates that M dwarfs with spectral types ranging from M3 /…
The physics of brown dwarfs has continuously improved since the discovery of these astrophysical bodies. The first important developments were devoted to the description of their mechanical structure, with the derivation of an appropriate…
A suite of discoveries in the last two decades demonstrate that we are now at a point where incorporating magnetic behavior is key for advancing our ability to characterize substellar and planetary systems. The next decade heralds the…
We report on nine wide common proper motion systems containing late-type M, L, or T companions. We confirm six previously reported companions, and identify three new systems. The ages of these systems are determined using diagnostics for…
The formation of brown dwarfs (BDs) poses a key challenge to star formation theory. The observed dearth of nearby ($\leq 5$ AU) brown dwarf companions to solar-mass stars, known as the brown dwarf desert, as well as the tendency for…
Several tens of white dwarfs are known to host circumstellar discs of dusty debris, thought to arise from the tidal disruption of rocky bodies originating in the star's remnant planetary system. This paper investigates the evolution of such…
The formation and early evolution of low mass young stellar objects (YSOs) are investigated using three-dimensional non-ideal magneto-hydrodynamics simulations. We investigate the evolution of YSOs up to ~ 10^4 yr after protostar formation,…
Angular momentum loss requires magnetic interaction between the forming star and both the circumstellar disk and the magnetically driven outflows. In order to test these predictions many authors have investigated a rotation-disk connection…
Stellar rotation is a crucial parameter driving stellar magnetism, activity and mixing of chemical elements. Furthermore, the evolution of stellar rotation is coupled to the evolution of circumstellar disks. Disk-braking mechanisms are…
Protoplanetary disks are quasi-steady structures whose evolution and dispersal determine the environment for planet formation. I review the theory of protoplanetary disk evolution and its connection to observations. Substantial progress has…
The evolution of circumstellar discs is influenced by their surroundings. The relevant processes include external photoevaporation due to nearby stars, and dynamical truncations. The impact of these processes on disc populations depends on…