We have obtained series of images in the near infrared J and Ks bands for seven L-type dwarfs with a duration of 3 to 6 hours. We present results on: 1) the amplitude of variability associated with atmospheric changes over time scales from minutes to several hours; 2) the search for cool companions in wide orbits; 3) the search for transits of brown dwarfs and planetary companions in very close orbits.

We present results of two observing campaigns aimed at characterising variability of the L2 brown dwarf Kelu-1. The first campaign in March 2000 detected photometric variability at the 1.2% level, with a strong period of 1.8 hours. Followup spectroscopic observations with the VLT in February 2002 show no evidence of significant variability in the dust sensitive molecular lines, but do show evidence for variability in the EW(Hα) with a period of 1.8 hours. Radial velocity measurements rule out a close substellar companion. Kelu-1 appears to be a single brown dwarf with a rotation period of 1.8 hours.

We construct Ks-band light curves for nine field L and T brown dwarfs using the Palomar 60 inch Telescope. Results of a robust statistical analysis indicate that about half the targets show significant evidence for variability. Two of these variable targets have marginally significant peaks in the Lomb-Scargle periodogram. The phased light curves show evidence for periodic behavior on timescales of about 1.5 and 3.0 hours.

We have established an international collaboration, named CLOUDS, to investigate atmospheric variability in L and T dwarfs. Our aim is to provide continuous and simultaneous observations over a wide range of wavelengths, using various techniques. We observed 15 targets of types between M9.5 to T6.5, from the optical to the mid infrared, in photometry and/or spectroscopy. Here we present the data set.

The joint U.S. and German SOFIA project to develop and operate a 2.5-meter infrared airborne telescope in a Boeing 747-SP is now well into development. First science flights will begin in 2004. The observatory is expected to operate for over 20 years. The sensitivity, characteristics and science instrument complement are discussed. SOFIA will have a number of experiments related to Brown Dwarf research; some of these are discussed.

Over the past two decades, infrared detector arrays have evolved from small, highly experimental devices to large format arrays being used in numerous facility class instruments. The next generation of infrared arrays will allow the design of mosaic instruments with very large fields of view that offer exciting new opportunities for large scale surveys in the infrared.

During the final quarter of 2003, UKIRT will take delivery of WFCAM. This new wide–field camera will have a FOV of 0.2 square degrees, and is therefore well suited to large–scale survey work. A consortium of more than 60 astronomers has successfully bid for a large fraction of all UKIRT time over the next 5 years to undertake several public surveys using this new facility. These surveys are collectively known as the UKIRT Infrared Deep Sky Survey (UKIDSS). In this short paper I will describe the project and review the prospects for BD research using UKIDSS data, highlighting some of the major science goals related to BDs that we hope will be achieved.

The recently installed Adaptive Optics system NAOS now offers diffraction limited images at the VLT. Together with the CONICA camera, NAOS provides the possibility to perform high dynamical range observations in the near IR domain. We present here NAOS-CONICA (hereafter NACO) capabilities as well as the first images of binaries obtained during NACO commissioning.

General arguments for optimized coronagraphy in the search for planets are presented. First, off-axis telescopes provide the best telescopic platforms for use with coronagraphy, and telescope fabrication technology now allows the fabrication of such telescopes with diameters of up to 6.5 m. We show that in certain circumstances a smaller telescope with an off-axis primary has a signal-to-noise advantage compared with larger Cassegrain telescopes. Second, to fully exploit the advantages of the coronagraph for suppressing stray light, it is necessary to use a high Strehl ratio adaptive optics system. This can be best achieved initially with modest aperture telescopes of 3–4 m in diameter. Third, application of simultaneous differential imaging and simultaneous polarimetric techniques are required to reach the photon-limit of coronagraphic imaging. These three developments, if pursued together, will yield significant improvements in the search for planets.

The Next Generation Sky Survey (NGSS) is a proposed NASA MIDEX mission to map the entire sky in four infrared bandpasses – 3.5, 4.7, 12, and 23 μm. The seven-month mission will use a 50-cm telescope and four-channel imager to survey the sky from a circular orbit above the Earth. Expected sensitivities will be half a million times that of COBE/DIRBE at 3.5 and 4.7 μm and a thousand times that of IRAS at 12 and 23 μm. NGSS will be particularly sensitive to brown dwarfs cooler than those presently known. Deep absorption in the methane fundamental band at 3.3 μm and a predicted 5-μm overluminosity will produce uniquely red 3.5-to-4.7 μm colors for such objects. For a limiting volume of 25 pc, NGSS will completely inventory the Solar Neighborhood for brown dwarfs as cool as Gl 229B. At 10 pc, the census will be complete to 500 K. Assuming a field mass function with α = 1, there could be one or more brown dwarfs warmer than 150 K lying closer to the Sun than Proxima Centauri and detectable primarily at NGSS wavelengths. NGSS will enable estimates of the brown dwarf mass and luminosity functions to very cool temperatures and will provide both astrometric references and science targets for NGST.

The first astrometric procedure for the detection of Brown Dwarfs as a double star component was accomplished for the HIPPARCOS project, using Fourier series for the description of the orbital motion of Brown Dwarfs, in connection with classical least squares techniques for the estimation of all relevant unknowns. The disadvantage of this procedure was an insufficient number of false decisions. Modern techniques of time series analysis allows a much better mathematical treatment of the physical phenomena. With respect to the large number of candidate objects and the enhanced accuracy of the new astrometric satellites, the introduction of a new approach for the astrometric detection of Brown Dwarfs is suggested.

We propose a near-infrared microlensing survey of the central 2 degree field of the Galactic Center, in an attempt to estimate the surface density and mass distribution of distant free-floating brown dwarfs in the bulge and in the disk, acting as lenses of bright stars towards the Galactic Center. We estimate the probability (optical depth) of microlensing events to be 10-7 and the typical timescale (full-width) of the amplification lightcurve to be about 1 week. The necessary wide-field NIR survey technology should soon be available on UKIRT, CFHT, and with VISTA at ESO/Paranal.

We discuss the prospects for brown dwarf detections in the field and in star-forming regions using data from the SIRTF Legacy Science Programs. We concentrate in particular on the SIRTF Wide-area InfraRed Extragalactic survey (SWIRE) and “From Cores to Disks” program (c2d). The SWIRE program will map up to 70 square degrees of high galactic latitude sky, providing wavelength coverage from 3.6 to 160 μm. SWIRE's estimated 5σ sensitivity of 10 microJy at 4.5 μm and its relatively large areal coverage will make it uniquely sensitive to the population of extremely cool (T ≤ 600 K) field brown dwarfs thus far undetected in other surveys. The “c2d” program will map up to 20 square degrees in nearby (d ≤ 300 pc) star-forming molecular clouds over the wavelength range 3.6 – 70 microns, potentially detecting young brown dwarfs down to a few MJupiter. Taken together, these two SIRTF datasets will offer a unique opportunity to take a census of the low mass/temperature members of the brown dwarf population.

We present a summary of SIRTF capabilities and the observing strategy for the SIRTF Cores to Disks Legacy Project.

We present to the brown dwarf community the Near Infrared Coronographic Imager (NICI), which is being built for installation in 2005 on the Gemini South Telescope. NICI's dual channel architecture and dedicated AO system are designed to permit deep circumstellar discrimination of faint sources where some spectral key can be used to get a simultaneous estimate of the background. One of the principal science goals of NICI is to search for ultracool companions to stars and brown dwarfs.

The proposed Eclipse Discovery mission is an optical space telescope designed to provide a thousandfold reduction in scattered light near bright stars in comparison to any Hubble Space Telescope instrument. A survey of 500 single stars within 15 pc can detect companions with absolute z magnitude of 22 at separations > 10 AU in most of the targets. Spectrophotometry of CH4 and H2O bands between 0.8-1.0 μm can be used to derive the effective temperatures of the objects. The ECLIPSE brown dwarf survey would directly measure the luminosity function of brown dwarf companions down to ~20 Jupiter masses, providing a crucial comparison with field objects.

Determining the process(es) by which brown dwarfs form is key to understanding their intrinsic nature. If their origins are within circumstellar disks they are akin to giant planets. If, on the other hand, they coalesce from molecular cloud cores, then they share a common lineage with low mass stars. These two mechanisms can be distinguished by investigation of young (< 10 Myr) substellar objects. If brown dwarfs are small failed stars, we expect to find very low mass analogs of the Classical T Tauris, with primordial magnetic fields from the molecular cloud collapse. Accretion onto these objects leads to characteristic magnetic activity signatures such as chromospheric and coronal emission resulting in an ultraviolet excess continuum.

The Orion OB1b association (m-M = 7.9, 2 Myr) provides a laboratory for following the strength and occurrence of the accretion process as a function of mass. Studies of the substellar mass function within the sigma Orionis cluster at the southern end of the association indicate that brown dwarfs are common. Based on model isochrones and the SDSS M dwarf sequence we expect the 95% completeness limit of the “Orion” scans to correspond to 0.1 and 0.03 solar masses for the u and g bands.

The question of what sort of guidelines should be used to classify substellar mass objects was considered and debated during an evening panel discussion at the IAU 211 Symposium on Brown Dwarfs.

The subject of brown dwarfs has grown enormously since the announcement of the first brown dwarfs in 1995. Thus this conference is the largest conference ever devoted solely to brown dwarfs, with 150 delegates, 82 talks and 52 posters. This summary will struggle, therefore, to give a complete picture and, of course, it is only the impression of one individual.