Search for Millisecond Periodicities in Type I X-ray Bursts of the Rapid   Burster
  We have searched the rising portion of type I X-ray bursts observed from the Rapid Burster with the Rossi X-ray Timing Explorer for the presence of periodicities. The 95 per cent confidence upper limit on the average root-mean-square variation of near coherent pulsations with a width of <1 Hz (in 60--2048 Hz) during the first second of the bursts is <8.8 per cent. We find a possible detection (>98 per cent significance) at 306.5 Hz. 
D.W. Fox (1), W.H.G. Lewin (1), R.E. Rutledge (2), E.H. Morgan (1), R.   Guerriero (3), L. Bildsten (4), M. van der Klis (5)...