Spectral and accretion evolution of H1743−322 during outbursts in RXTE era

Abstract

Aims. We study the spectral evolution of the H1743−322 during outbursts in the RXTE era. We aim to connect the variation of the spectral parameters with the accretion parameters along with the progress of the outbursts. We understand the evolution of the accretion parameters and hence the dynamics of the accretion process in light of the irradiated disc instability model. Methods. We provide a comprehensive study of all the outbursts of H1743−322 between 2003 and 2011. We performed spectral modelling of all the RXTE/PCA observations using phenomenological models. Also, we carried out spectral modelling by a hydrodynamic accretion flow model and estimated the accretion parameters. We applied the irradiated disc instability scenario in the presence of both Keplerian and sub-Keplerain accretion components to understand the evolution of accretion parameters. For this purpose, we propose a toy model for the time variation of the accretion rates following a powerlaw during outbursts. Results. All of the outbursts show spectral state transitions in the hardness-intensity diagram. The 2003 and 2004 outbursts are long-duration outbursts and relatively softer than the other outbursts. The 2008b and 2011 outbursts provide a unique opportunity to estimate the critical accretion rate (ṁdc) for triggering an outburst in this system within a narrow range of 0.076 < ṁdc < 0.086 (in Eddington units). In the absence of any dynamical measurement, we attempt to constrain a few orbital parameters of the system using an assumed mass and ṁdc in the range.