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 (Porb≈7.69±0.02hr$$ {P}_{\mathrm{orb}}\approx 7.69\pm 0.02\kern0.22em \mathrm{hr} $$), GRO J0422+32 (Porb≈5.091850±0.000005hr$$ {P}_{\mathrm{orb}}\approx 5.091850\pm 0.000005\kern0.22em \mathrm{hr} $$) and Swift J1753.5‐0127 (Porb≈3.244±0.001hr$$ {P}_{\mathrm{orb}}\approx 3.244\pm 0.001\kern0.22em \mathrm{hr} $$). 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 Porb=16.9hr$$ {P}_{\mathrm{orb}}=16.9\kern0.22em \mathrm{hr} $$ 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.