Mini-outburst of black hole X-ray binary GX 339-4 in 2004

The mini -outburst of black hole X-ray binaries (BHXBs) is a re -bright event of light curve, which is often detected in BHXBs with the low orbital period, such as XTE J1650-500 (P-orb approximate to 7.69 +/- 0.02 hr), GRO J0422+32 (P-orb approximate to 5.091850 +/- 0.000005 hr) and Swift J1753.5-0127 (P-orb approximate to 3.244 +/- 0.001 hr). Because of its low X-ray luminosity, the physics properties of mini -outburst is still unclear. GX 339-4 is a famous BHXBs with the orbital period P-orb = 16.9 hr and present many normal outburst and failed outburst over the past decades. However, the mini -outburst is not still detected in GX 339-4. In this work, using the Rossi X-ray Timing Explorer (RXTE) observations, we investigated the energy spectrum properties of the GX 339-4 outburst in 2004 and confirmed that the outburst in 2004 is a mini -outburst. It is very interest that the mini -outburst has been through a whole state transition from Low/Hard state to High/Soft state. We also give a comparison between the normal outburst in 2002 and the mini -outburst in 2004. And we find that the two outburst present a similar Hardness -Intensity diagram and spectral properties, which suggest that the normal outburst and mini -outburst have a similar physics. We think that the mini -outburst of GX 339-4 in 2004 can be well explained by the disk instability model.