相关论文: Binary Formation Mechanisms: Constraints from the …

We provide an analysis of the mass ratio distribution as gathered from almost all of the 559 orbital solutions derived by Professor Roger Griffin in his long series in the Observatory Magazine about "Spectroscopic Binary Orbits from…

Any predictive theory of star formation must explain observed variations (or lack thereof) in the initial mass function. Recent work suggests that we might expect quantitative variations in the IMF as a function of metallicity (Larson 2005)…

One of the nearest and best studied open clusters, Pleiades is an important cornerstone of stellar astrophysics. Despite its role as reference coeval stellar population, its multiplicity properties remain vaguely determined. The combined…

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…

We present preliminary results of a radial-velocity search for companions to a volume limited sample of M dwarfs. Typical accuracy range between 10m/s for the brighter stars and 70m/s at our limiting magnitude. We complement the radial…

We present the first prediction for the mass distribution function of Galactic free-floating planets (FFPs) that aims to accurately include the relative contributions of multiple formation pathways and stellar populations. We derive our…

A major outstanding question regarding the formation of planetary systems is whether wide-orbit giant planets form differently than close-in giant planets. We aim to establish constraints on two key parameters that are relevant for…

Our first aim is to calculate the minimum mass for Primary Fragmentation in a variety of potential star-formation scenarios, i.e. (i) hierarchical fragmentation of a 3-D medium; (ii) one-shot, 2-D fragmentation of a shock-compressed layer;…

We review recent advances in our understanding of the origin of the initial mass function (IMF). We emphasize the use of numerical simulations to investigate how each physical process involved in star formation affects the resulting IMF. We…

We have observed a large sample of spectroscopic binary stars in the Hyades Cluster, using high resolution infrared spectroscopy to detect low mass companions. We combine our double-lined infrared measurements with well constrained orbital…

We present the results of a search for companions to young brown dwarfs in the Taurus and Chamaeleon I star forming regions (1/2-3 Myr). We have used WFPC2 on board HST to obtain F791W and F850LP images of 47 members of these regions that…

The current knowledge on the stellar IMF is documented. It appears to become top-heavy when the star-formation rate density surpasses about 0.1Msun/(yr pc^3) on a pc scale and it may become increasingly bottom-heavy with increasing…

Binary population synthesis provides a direct way of studying the effects of different choices of binary evolution models and initial parameter distributions on present-day binary compact merger populations, which can then be compared to…

Sun-like stars are known to host a paucity of brown dwarf companions at close separations. Direct imaging surveys of intermediate-mass stars have suggested that the brown dwarf desert may be fundamentally a feature in the mass ratio.…

The combination of a finite time-scale for star formation, rapid early stellar evolution and rapid stellar-dynamical processes imply that the stellar IMF cannot be inferred for any star cluster independently of its age (the Cluster IMF…

(Abreviated) FS CMa stars belong to a diverse group of stars exhibiting the B[e] phenomenon, which is manifested mainly by the presence of forbidden emission lines and a~strong infrared (IR) excess in their spectra. Recently, a strong…

Observations indicate that the central portions of the Present-Day Prestellar Core Mass Function (CMF) and the Stellar Initial Mass Function (IMF) both have approximately log-normal shapes, but that the CMF is displaced to higher mass than…

The observed similarities between the mass function of prestellar cores (CMF) and the stellar initial mass function (IMF) have led to the suggestion that the IMF is already largely determined in the gas phase. However, theoretical arguments…

We have conducted an angular differential imaging survey with NIRC2 at Keck in search of close-in substellar companions to a sample of seven systems with confirmed planetary-mass companions (PMCs) on wide orbits (>50 AU). These…

To better understand the evolution of stars in binary systems as well as to constrain the formation of binary stars, it is important to know the binary mass-ratio distribution. However, in most cases, i.e. for single-lined spectroscopic…