A comparative study on the spectra of normal outburst and mini‐outbursts of black hole X‐ray binary XTE J1550‐564

Abstract

One normal outburst and three mini‐outbursts have been detected by Rossi X‐ray Timing Explorer (RXTE) satellite after 2000 in the well‐known black hole X‐ray binary XTE J1550‐564. In our work, we explored the energy spectral properties of the four outbursts and the three mini‐outbursts retained in the Low/Hard state. The results show that the X‐ray spectra of the three mini‐outbursts are harder than that of normal outburst and have no disk component. In the correlation analysis, the anti‐relationship of the three mini‐outbursts suggested that it may be a result of the incomplete evolutionary success of Shakura‐Sunyaev disk. The whole X‐ray spectral correlation evolution shows well the state transition from the Shakura‐Sunyaev disk to the advection‐dominated accretion flow. We think that the three mini‐outbursts may originated from a small discrete accretion event.