Rapid Spectral Variability during the 2003 Outburst of V4641 Sgr (= SAX   J1819.3-2525)
  The black hole candidate V4641 Sgr (= SAX J1819.3-2525) went through a brief outburst during 2003 Aug 01 to Aug 08. During the outburst, activity was noted in optical, radio as well as X-rays. Here we present results of Spectral and Temporal analysis of a pointed Rossi X-ray Timing Explorer (RXTE) observation of the source during the outburst. During this pointing we observed flaring activities with associated X-ray luminosity variations over factors of 5 or more in timescales of few tens of seconds. The observed flares during are intrinsically different in their spectral and temporal properties. We see evidence of variable column density during one of the flares. The spectral and temporal analyses of the data suggest occasional outflow/mass ejection. 
Dipankar Maitra and Charles D. Bailyn