Another canonical time variation of X-rays from black hole candidates in the very high flare state?

Abstract

An X-ray nova, Nova Muscae 1991 or GS 1124-68, was observed with the LAC on board Ginga. On 1991 January 22, 7 days after its X-ray maximum, the same time variations were discovered as those observed in GX 339-4 at its near-flare maximum. The phase lags between different energy X-ray showed a peculiar large and broad peak, which was the same as that observed in GX 339-4. Shapes of the power spectrum density functions were similar, and indices of the power-law component of the X-ray energy spectra were the same. These suggest that in some black hole candidates, the same X-ray production processes are taking place in the very high flare state. We also confirmed the canonical time variations of X-rays of GS 1124-68 in the low state.