X-ray outburst from the direction of the Galactic Centre.

A transient point X-ray source Al742-28 has been observed in the galactic center by the Ariel 5 rotation modulation collimator (RMC) experiment. Its rise to a peak and subsequent decline by a factor of two over 12 d were monitored. The position was found to be alpha equals 17h 42 min 26.0 plus or minus 4.8s, delta equals minus 28 degrees 59.8 plus or minus 1.2 min (1950.0 coordinates, 90% confidence limits). The rise and turnover of the X-ray light curve, occurring on a time scale of the order of 2 d, probably implies an emission region less than 0.002 pc in diameter. The position and error box indicates that Al742-28 is directly associated with one of the radio or infrared sources within Sgr A.