GAS AROUND BETA-PICTORIS - AN UPPER LIMIT ON THE HI CONTENT

The observed gas and dust disk around the main sequence star beta Pict oris suggests that neutral hydrogen clouds could surround the star. We present an observational attempt to detect such a cloud through its 2 1 cm line emission. No HI emission was detected. Upper limits on the c olumn density of a HI cloud around beta Pictoris with synthesized beam s of sizes between 27 and 90 arcsecs are given. The 3 sigma upper limi t is less than 0.5% of the mass of Jupiter for a wide range of possibl e distributions of that mass. The inferred gas to dust ratio is less t han 10 and indicates that most of the original gas present in the prot oplanetary nebulae has been processed or expelled.