Number 268 (Story #3), May 1, 1996 by Phillip F. Schewe and Ben Stein THE FIRST BINARY-STAR SYSTEMS BEAMING X RAYS AT SUB-MILLISECOND rates have been observed by the Rossi X-Ray Timing Experiment, an orbiting telescope launched in December 1995. Speaking at this week's meeting of the American Astronomical Society in San Diego, RXTE scientists reported that a binary system (Sco X-1) in the constellation Scorpius was emitting x rays on and off 1130 times per second. Another binary system (4U 1728-34) in the constellation Sagittarius was emitting x ray bursts at a rate of up to 1100 per second. In each case the x rays are believed to arise when material from a normal star falls onto a companion neutron star. For Sco X-1, x rays beamed at a slower rate are also seen. The researchers are puzzled as to why the slower pulses and the faster 1130 pulses/sec emissions are modulating over time in the same way. (AAS press release.)