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 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 1705À44, and XTE J1550À564, providing further support for the idea 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).

A Hard‐to‐Soft State Transition during a Luminosity Decline of Aquila X‐1

“…In all other outbursts of Aql X-1, as well as in the outbursts of several other transient sources such as GX 339À4 (Yu et al 2007), the state transitions were associated with the luminosity peaks of the LH states (Yu et al 2003(Yu et al , 2007YKF04). Thus, it is the luminosity of the hard-to-soft state transition, instead of the peak luminosity of the LH state before the state transition, that is correlated with the peak luminosity of the following HS state.…”

“…There is additional evidence that the hard, power-law spectral component is associated with the mass in the disk. In the black hole transient GX 339À4, the peak fluxes of the LH states in the seven outbursts seen by BATSE and HEXTE in the past 15 years are nearly linearly related to the outburst waiting time (Yu et al 2007). The correlation also suggests that the earlier accretion flow that powers the LH state and the later accretion flow that powers the HS state are somehow related, suggesting that the outer disk plays a role in the generation of the hard spectral component that dominates the X-ray emission in the LH state (YKF04; Yu et al 2007).…”

“…In the black hole transient GX 339À4, the peak fluxes of the LH states in the seven outbursts seen by BATSE and HEXTE in the past 15 years are nearly linearly related to the outburst waiting time (Yu et al 2007). The correlation also suggests that the earlier accretion flow that powers the LH state and the later accretion flow that powers the HS state are somehow related, suggesting that the outer disk plays a role in the generation of the hard spectral component that dominates the X-ray emission in the LH state (YKF04; Yu et al 2007). A similar correlation in the flaring neutron star LMXB 4U 1705À44 (YKF04; W. Yu 2007, in preparation) indicates that the phenomena are associated with the variation of the mass accretion rate in the accretion flow, rather than the outburst mechanism of soft X-ray transients (e.g., Cannizzo et al 1995).…”

Outbursts from IGR J17473-2721

“…GX 339-4 stayed in a hard state for 500 days prior to transition to a soft state within roughly 100 days. The entire outburst lasted for at least 400 days, if the start time is the transition to soft state (Yu et al 2007;Belloni et al 1999). The outburst of IGR J17473-2721 is more similar to GX339-4 based on their long-lived preceding outburst in hard X-rays.…”

Leptonic/hadronic models for electromagnetic emission in microquasars: the case of GX 339-4

“…The source goes through all the spectral states of X‐ray binaries: low–hard, high–soft, very high state, intermediate state and quiescence (McClintock & Remillard 2006). It frequently displays outbursts associated with state transitions, episodes during which the X‐ray luminosity can reach peaks of L X = 10 37−38 erg s −1 for an assumed distance of 6 kpc (Homan et al 2005; Yu et al 2007). It was after the X‐ray outburst of 2002 that Gallo et al (2004) imaged for the first time a relativistic radio jet on ∼10 3 au scales in the system (see also Corbel et al 2000).…”