Peak Luminosities of the Hard States of GX 339‐4: Implications for the Accretion Geometry, Disk Mass, and Black Hole Mass

Abstract

We have analyzed observations of the black hole transient {GX 339$-$4} made with the {\it Rossi} X-ray Timing Explorer (RXTE) and the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma-ray Observatory (CGRO). We have found a nearly linear relation between the peak flux during the low/hard (LH) state that occurs at the beginning of an outburst and the time since the flux peak of the latest LH state identified in the previous outburst. Assuming that the rate at which mass accumulates in the accretion disk between these peaks is constant and that any mass that remains in the disk after an outburst has a negligible effect on the next outburst, this nearly linear relation suggests that the peak flux during the LH state that occurs at the beginning of an outburst is related to the mass in the disk, and thus that the entire disk is probably involved in powering these LH states. We have also found a positive correlation between the peak luminosities of the LH state in the three recent outbursts of {GX 339$-$4} and the peak luminosities of the following HS state. This correlation is similar to the correlations reported previously for {Aql X$-$1}, {4U 1705$-$44}, and {XTE J1550$-$564}, providing further support that the accretion flow that powers the LH state is related to the accretion flow that powers the following HS state. Although the luminosity of the LH-to-HS transition varies by up to an order of magnitude, the neutron stars and the black holes are distinguishable in the state transition luminosity. We discuss the implications for the mass determination of the compact stars in the ultraluminous X-ray sources (ULXs).