Abstract Details

Affiliation: pt. Ravishankar shukla university
Conference ID: ASI2017_409
Title : Systematic Spectral Analysis of Low/Hard State of GX 339-4 During Four Outbursts to Investigate the Truncation of Accretion Disk
Authors and Co-Authors : Ranjeev Misra (IUCAA),J.S.Yadav (TIFR),S.K.Pandey (PTRSU,Raipur)
Abstract Type : Oral
Abstract Category : Extragalactic astronomy
Abstract : The canonical low/hard states of black hole binaries are generally explained in terms of truncation of the standard accretion disk at larger radii and the inner regions are replaced by the hot inner flow giving rise to the hard X-ray flux via Comptonization. This is empirically supported by the smaller values of photon index ~1.7 (<2) implying that the hot medium is seed photons starved. On the other hand, the presence of a broad Iron line found on several occasions during the hard state indicates that the accretion disk is not truncated but extends all the way to the inner most stable orbit. If this is the case, the hot inner flow should not be photon starved, contrary to the observational results. The broad Iron line should be accompanied by a broad smeared reflection bump at ~30 keV and it maybe that this additional component makes the spectrum hard and the intrinsic photon index is larger, i.e. > 2. This would mean that the medium is not photon deficient, reconciling the presence of a broad Iron line in the hard state. To test this hypothesis, we have analyzed the RXTE observations of GX 339-4 during its four outbursts and identify the observations when the system was in the hard state and showed a broad Iron line. We have made an attempt to fit these observations with models which include smeared reflection to understand whether the intrinsic photon index can indeed be large. We present the results of this analysis and other correlations between spectral parameters such as the flux, ionization level, Equivalent Width of the line, etc.