TITLE: GCN GRB OBSERVATION REPORT NUMBER: 333 SUBJECT: BeppoSAX: A new fast X-ray transient DATE: 99/05/20 15:55:58 GMT FROM: Luigi Piro at IAS/CNR Frascati Luigi Piro, on behalf of the BeppoSAX team, reports: Note: we have decided to distribute this info to the BeppoSAX GRB alert list due to the potential association of these events (or some of those) with GRB. On May 20 at 2:02:58 UT a fast X-ray transient, which we designate 1SAX J0835.9+5118, was detected by one of the BeppoSAX WFC (n.1). The event lasted about 10 s., with a peak flux of about 1 Crab in the 2-25 keV range. The position is (equinox 2000) R.A.=128.98, decl=51.31, with an error radius of 3'. No previously known X-ray source lies in the error box. At a preliminary analysis no simultaneous signal was detected by the GRBM (40-700 keV). Follow up observations are encouraged to investigate the nature of this object. [GCN OP NOTE: I am allowing this BeppoSAX Circular on a new x-ray transient to be distributed because (as pointed out) of the potential association of this type of event with GRBs. I realize this is outside the scope of the Circulars in the strictess definition, but the potential is there and it seems a small price to pay at this point in time. It also serves to explore this area for a future growth/expansion of the Circular service. As always, I welcome comments from the community on the content and operations of the Circular service. CGRO-BATSE was in a "triggers disabled" mode (it was inside the N.American Trigger Disable Box) during SAX-WFC transient time. The LAD high voltage was on and the SAX RA,Dec location was visible (not earth occulted), so any data and analysis will be delayed until tomorrow to determine if BATSE actually detected this event or not.]