相关论文: The substellar mass function in the central region…

A complete accounting of nearby objects -- from the highest-mass white dwarf progenitors down to low-mass brown dwarfs -- is now possible, thanks to an almost complete set of trigonometric parallax determinations from Gaia, ground-based…

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…

In 2022, the James Webb Space Telescope (JWST) obtained 1-5um images of the center of the Orion Nebula Cluster (ONC). I have analyzed these data in an attempt to search for substellar members of the cluster. Using a pair of color-color…

A high number of embedded clusters is found in the Galaxy. Depending on the formation scenario, most of them can evolve to unbounded groups that are dissolved within a few tens of Myr. A systematic study of young stellar clusters showing…

We have determined the mass functions, mass-ratio distribution functions and fractions of binary stars with mass ratios above particular thresholds for radially-separated populations of stars in the nearby open clusters Hyades and Praesepe.…

Studying the accretion process in very low-mass objects has important implications for understanding their formation mechanism. Many nearby late-M dwarfs that have previously been identified in the field are in fact young brown dwarf…

Brown dwarfs with well-determined ages, luminosities, and masses provide rare but valuable tests of low-temperature atmospheric and evolutionary models. We present the discovery and dynamical mass measurement of a substellar companion to HD…

Analysis of initial observations from near-infrared sky surveys has shown that the resulting photometric catalogues, combined with far-red optical data, provide an extremely effective method of finding isolated, very low-temperature objects…

Substellar multiplicity is a key outcome of the formation process. The biggest challenge for the next decade will be to distinguish between the formation history, environmental conditions, and dynamical evolution leading to the least…

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…

The cluster Praesepe (age 650 Myr) is an ideal laboratory to study stellar evolution. Specifically, it allows us to trace the long-term decline of rotation and activity on the main-sequence. Here we present rotation periods measured for…

We present a CCD-based photometric survey covering 870 sq. arcmin in a young stellar cluster around the young multiple star sigma Orionis. Our survey limiting R, I, and Z magnitudes are 23.2, 21.8, and 21.0, respectively. From our…

We have used 3.5 to 8 micron data from the Cores to Disks (c2d) Legacy survey and our own deep IJHKs images of a 0.5 square degree portion of the c2d fields in Ophiuchus to produce a sample of candidate young objects with probable masses…

We investigate the star formation activity in a young star forming cluster embedded at the edge of the RCW 41 HII region. As a complementary goal, we aim at demonstrating the gain provided by Wide-Field Adaptive Optics instruments to study…

We derive and parametrize the Galactic mass function (MF) below 1 $\msol$ characteristic of both single objects and binary systems. We resolve the long standing discrepancy between the MFs derived from the HST and from the nearby luminosity…

We have employed precise V and I photometry of NGC 188 at WIYN to explore the cluster luminosity function (LF) and study the cluster white dwarfs (WDs). Our photometry is offset by V = 0.052 (fainter) from Sandage (1962) and Eggen & Sandage…

We use 2MASS photometry to study colour-magnitude and colour-colour diagrams, structure and mass distribution in the ionizing open cluster NGC\,6611. Reddening variation throughout the cluster region is taken into account followed by…

We report the present day mass functions (PDMFs) of 3 young open clusters over a mass range from 30 Jupiter masses to 10~\msunn. The PDMFs of the 3 clusters are remarkably similar, suggesting little impact of specific conditions (stellar…

(Abridged) We present high-resolution HST imaging in the optical (WFPC2) and near-infrared (NICMOS) of a disk region 1 kpc NE of the starburst core in the nearby galaxy M82. This region, M82 ``B,'' has been suspected to be a fossil…

Observed variations in the IMF are reviewed with an emphasis on environmental density. The remote field IMF studied in the LMC by several authors is clearly steeper than most cluster IMFs, which have slopes close to the Salpeter value.…