A search for companions to nearby brown dwarfs: The binary DENIS-PJ1228.2-1547

Hubble Space Telescope imaging observations of two nearby brown dwarfs, DEN IS-P J1228.2-1547 and Kelu 1, made with the near-infrared camera and multio bject spectrometer (NICMOS), show that the DENIS object is resolved into tw o components of nearly equal brightness with a projected separation of 0.27 5 are second (5 astronomical units for a distance of 18 parsecs), This bina ry system will be able to provide the first dynamical measurement of the ma sses of two brown dwarfs in only a few years. Upper Limits to the mass of a ny unseen companion in Kelu 1 yield a planer of 7 Jupiter masses aged 0.5 x 10(9) years, which would have been detected at a separation Larger than ab out 4 astronomical units. This example demonstrates that giant planets coul d be detected by direct imaging if they exist in Jupiter-like orbits around nearby young brown dwarfs.