Circular No. 6437
KS 1731-260
     E. H. Morgan and D. A. Smith, Massachusetts Institute of
Technology, report:  "RXTE observations of KS 1731-260 performed on
July 14.10-14.29 UT show persistent emission of 250 mCrab and a
single type-I burst with a peak emission of 1.5 Crab at July 14.18.
The total burst duration is 30 s, with a FWHM of 6 s in the band 2-
60 keV.  During the peak of the burst, a periodic signal at 524 Hz
is detected.  This signal is only seen for two seconds, starting 2
s after the rising edge of the burst.  The pulse fraction is 12 +/-
2 percent.  This 524-Hz signal is similar to the 363-Hz signal
found only during bursts from 4U 1728-34 (IAUC 6387).  No periodic
or quasiperiodic signals are detected in the persistent emission or
in the tail of the burst.  We speculate that we have detected the
rotation frequency of the neutron star, in which case the spin
period is 1.91 ms."

                      (C) Copyright 1996 CBAT                    
1996 July 22                   (6437)            Daniel W. E. Green