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Description
Black hole X-ray binaries (BHXRBs) undergo hard-soft-hard state during their outbursts. In the soft state, the energy spectrum is dominated by thermal emission from the accretion disk, which is thought to extend down to the innermost stable circular orbit. In contrast, during the hard state, the disk is truncated at a larger radius, and the spectrum is dominated by a comptonization component from a corona. Recent observations of the 2018 outburst of MAXI J1820+070 provide evidence for the formation of a magnetically arrested disk. A key indicator of this phenomenon is the observed deviation from the exponential decay of disk luminosity, which suggests the disk is receding. In this work, we analyze RXTE data from 16 BHXRBs, fitting their X-ray spectra to separately determine the luminosities of the disk and the corona. We find that the disk luminosity in the soft state generally follows an exponential decay. Although some sources lack data for the soft-hard state transition and others exhibit more complex light curves during their decay phases, seven sources show evidence of disk receding during the soft-hard state transition, accompanied by a flare in the comptonization component. Our results demonstrate that the disk receding during the soft-hard state transition is a common feature in BHXRBs.
