The Discovery of an Outburst and Pulsed X-ray Flux from SMC X-2 from   RXTE Observations
  Rossi X-ray Timing Explorer All Sky Monitor observations of SMC X-2 show that the source experienced an outburst in January to April 2000 reaching a peak luminosity of greater than ~10^38 ergs s^-1. RXTE Proportional Counter Array observations during this outburst reveal the presence of pulsations with a 2.37s period. However, optical photometry of the optical counterpart showed the source to be still significantly fainter than it was more than half a year after the outburst in the 1970s when SMC X-2 was discovered. 
R.H.D. Corbet, F.E. Marshall, M.J. Coe, S. Laycock, & G. Handler