Found 18 talks width keyword brown dwarfs

We report on the discovery of a fourth component in the HD 221356 star system, previously known to be formed by an F8V, slightly metal-poor primary ([Fe/H]= -0.26), and a distant M8V+L3V pair. In our ongoing common proper motion search based on VISTA Hemisphere Survey (VHS) and 2MASS catalogues, we have detected a faint (J = 13.76 ± 0.04 mag) co-moving companion of the F8 star located at a projected distance of ~312 AU. Near-infrared spectroscopy of the new companion indicates an L1±1 spectral type. Using evolutionary models the mass of the new companion is estimated at ~0.08 solar masses, which places the object close to the stellar-substellar borderline. This multiple system provides an interesting example of objects with masses slightly above and below the hydrogen burning mass limit.

For the first time, we present the low-mass function of the entire young star cluster Sigma Orionis (3 Myr, 352 pc, no internal extinction) from 0.25 Msun through the brown dwarf regime down to 3-4 Mjup in the planetary-mass domain. We have used VISTA Orion data (ZYJHKs) in the magnitude interval J= 13 - 21 mag (completeness at J = 21.0 mag, Z = 22.6 mag, and 10 Mjup). Combined with Spitzer/IRAC (3.6 and 4.5 micron) and optical images (Iz-band) from our archives has allowed us to identify over 200 cluster low-mass member candidates in an area of 0.79 deg2, i.e., uncovering most of the cluster area. All of these objects have colors compatible with spectral types M, L, and T, i.e., Teff = 3000-1000 K. 23 of them are new planetary mass candidates in the Sigma Orionis cluster, thus doubling the number of cluster planetary mass objects known so far. By considering the Mayrit catalog, we have "extended" our mass function from 0.25 Msun up to the high-mass stars (O-type) of the cluster, covering four orders of magnitude in mass.

We present the completion of a program to cross-correlate the SDSS Data Release 1 and 2MASS Point Source Catalog in search for extremely red L and T dwarfs. The program was initiated by Metchev and collaborators, who presented the findings on all newly identified T dwarfs in SDSS DR1, and estimated the space density of isolated T0--T8 dwarfs in the solar neighbourhood. In the current work we present most of the L dwarf discoveries. Our red-sensitive (z-J > 2.75 mag) cross-match proves to be efficient in detecting peculiarly red L dwarfs, adding two new ones, including one of the reddest known L dwarfs. Our search also nets a new peculiarly blue L7 dwarf and, surprisingly, two M8 dwarfs. We further broaden our analysis to detect unresolved binary L or T dwarfs through spectral template fitting to all L and T dwarfs presented here and in the earlier work by Metchev and collaborators. We identify nine probable binaries, six of which are new and eight harbour likely T dwarf secondaries. We combine this result with current knowledge of the mass ratio distribution and frequency of substellar companions to estimate an overall space density of 0.005--0.05 pc^{-3} for individual T0--T8 dwarfs.

The proper characterization of the least massive population of the young Sigma Orionis star cluster is required to understand the form of the cluster mass function and its impact on our comprehension of the substellar formation processes. SOri70 (T5.5±1) and SOri73, two T-type cluster member candidates, would have likely masses between 3 and 7 MJup if their age is 3 Myr. SOri73 awaits confirmation of its methane atmosphere. Here I present the results of a search of T-type objects in an area of ~120 arcmin^2 in the Sigma Orionis cluster, the confirmation of the presence of methane absorption in SOri73 and the study of SOri70 and 73 cluster membership via photometric colors and accurate proper motion analysis. This results would have a dramatic impact in the cluster mass function, in one of the scenarios explored, they suggest a decrease in cluster members with planetary masses in the interval 3.5-6 Mjup.

Among the over 450 known exoplanets, the planets that transit their central star stand out, due to the wealth of information that can be gained about both planet and central star. The CoRoT mission has been designed to detect smaller and longer-periodic transiting exoplanets than can be found from ground observations. CoRoT-9b was detected by the satellite in summer 2008 and underwent follow-up observations from ground for another year. It stands out as having the largest periastron distance of all transiting planets, being expected to maintain permanently a moderate surface temperature, estimated between 250 and 430K. It is also the first exoplanet to which planet evolution models can be applied, without uncertain corrections that have been needed for 'hot' transiting planets. These models indicate it to be rather similar to Jupiter. Temperate gas-giant planets with low-to-moderate eccentric orbits constitute the largest group of currently known planets; they are probably similar to the gas giants of the solar system. With CoRoT-9b being this group’s first transiting planet, it may give rise to a much better understanding of these common planets. While CoRoT-9b itself is certainly not habitable, moons around it could be similar to Titan and provide some chance of habitability. Upcoming observations with the Spitzer space telescope are designed to improve on planet parameters and to perform a deeper search for the detection of its moons.

Up to now more than 400 extrasolar planets have been discovered, about 60 of them are transiting. Transiting extra-solar planets are particularly interesting, because their masses, diameters, densities and orientations of their orbits can be determined. Observations with the CoRoT Satellite have now turned up 10 transiting extrasolar planets. Although most of them are gas giants, it turns out that each of them is very special, and many of them have surprising properties. An unexpected discovery was for example the detection of emission lines from CoRoT 1b. Other interesting discoveries are CoRoT 2b, a planet orbiting a young star, and CoRoT 3b the first transiting brown dwarf orbiting a main sequence star. While the detection of transiting gas giants is interesting, the ultimate goal of CoRoT clearly was the detection of rocky planets. CoRoT has detected a solar-like star which shows transits that are only 0.03% deep. In this talk it it is demonstrated that this planet is in fact the first planet found outside our solar system from which we can firmly say that it is a rocky planet. New observations of this interesting object even constrain the properties of its exosphere.