相关论文: Sporadic and intense accretion in a 1 Myr-old brow…

We have identified a large sample of probable low mass members of the young open cluster IC2391 based on optical (VRIZ) and Infrared (JHK$_s$) photometry. Our sample includes 50 probable members and 82 possible members, both very low mass…

We present radial velocity measurements of a sample of L0-L8 dwarfs observed with VLT/UVES and Keck/HIRES. We combine these measurements with distance and proper motion from the literature to determine space motions for 43 of our targets.…

Using the largest high-resolution spectroscopic sample to date of young, very low mass stars (VLMS) and brown dwarfs (BDs), we investigate disk accretion in objects ranging from just above the hydrogen-burning limit all the way to nearly…

FU Tau belongs to a rare class of young, wide brown dwarf binaries. We have resolved the system in a Chandra X-ray observation and detected only the primary, FU Tau A. Hard X-ray emission, presumably from a corona, is present but,…

The Upper-Scorpius association is the OB association nearest to the Sun (145 pc). Its young age (5 Myr) makes it an ideal place to search for low-mass stars and brown dwarfs, as these objects should be relatively bright. We have performed a…

The mass and age of substellar objects are degenerate parameters leaving the evolutionary state of brown dwarfs ambiguous without additional information. Theoretical models are normally used to help distinguish between old, massive brown…

From the luminosity, effective temperature, and age of the Hyades brown dwarf 2MASSJ04183483+2131275 (2M0418), sub-stellar evolutionary models predict a mass in the range 39-55 Jupiter masses (M_Jup) which is insufficient to produce any…

Searches for companions of brown dwarfs by direct imaging mainly probe orbital separations > 3-10 AU. On the other hand, previous radial velocity surveys of brown dwarfs are mainly sensitive to separations smaller than 0.6 AU. It has been…

Context. Although many studies have been performed so far, there are still dozens of low-mass stars and brown dwarfs in the young sigma Orionis open cluster without detailed spectroscopic characterisation. Aims. We look for unknown strong…

We have determined astrometric positions for 15 WISE-discovered late-type brown dwarfs (6 T8-9 and 9 Y dwarfs) using the Keck II telescope, the Spitzer Space Telescope, and the Hubble Space Telescope. Combining data from 8 to 20 epochs we…

The continuous temporal coverage and high photometric precision afforded by space observatories has opened up new opportunities for the study of variability processes in young stellar cluster members. Of particular interest is the…

We present preliminary trigonometric parallaxes of 184 late-T and Y dwarfs using observations from Spitzer (143), USNO (18), NTT (14), and UKIRT (9). To complete the 20-pc census of $\ge$T6 dwarfs, we combine these measurements with…

We present high-quality, medium resolution X-shooter/VLT spectra in the range 300-2500 nm for a sample of 12 very low-mass stars in the \sigma Orionis cluster. The sample includes stars with masses ranging from 0.08 to 0.3 M$_\odot$. The…

We present results from a Herschel PACS survey of 8 brown dwarfs in the IC 2391 cluster. Our aim was to determine the brown dwarf disk fraction at ages of ~40-50 Myr. None of the 8 brown dwarfs observed were detected in the PACS 70 or 160mu…

We present imaging and spectroscopic observations with HST (WFPC2, ACS/HRC and STIS), VLT (FORS2) and Keck (HIRES) of the dM8 ultra-cool dwarf DENIS-P J185950.9-370632, located in the R-CrA region. The presence of lithium absorption at…

An investigation of the magnetospheric accretion and outflow signatures in sub-stellar objects is a natural extension of similar studies conducted on classical T Tauri stars (CTTS), and helps understand if brown dwarfs (BDs) follow the same…

We studied the properties of star formation and the characteristics of young stars in a quiet region located beyond the outskirts of the prominent star-forming cluster NGC 346 in the Small Magellanic Cloud (SMC). Utilising observations from…

We present the results of a search for brown dwarfs (BDs) and very low mass (VLM) stars in the 625 Myr-old, metal-rich ([Fe/H]=0.14) Hyades cluster. We performed a deep (I=23, z=22.5) photometric survey over 16 deg$^2$ around the cluster…

We report the discovery of a young planetary-mass brown dwarf in the rho Oph cloud core. The object was identified as such with the aid of a 1.5-2.4 micron low-resolution spectrum obtained using the NIRC instrument on the Keck I telescope.…

Extrasolar planet searches targeting very low-mass stars and brown dwarfs are hampered by intrinsic or instrumental limitations. Time series of astrometric measurements with precisions better than one milli-arcsecond can yield new evidence…