Two Years of INTEGRAL monitoring of GRS 1915+105 Part 2: X-Ray Spectro-Temporal Analysis

Abstract

(abridged) This is the second paper presenting the results of two years of monitoring of GRS 1915+105 with \integral and \rxte and the Ryle Telescope. We present the X-ray spectral and temporal analysis of four observations which showed strong radio to X-ray correlations. During one observation GRS 1915+105 was in a steady state, while during the three others it showed cycles of X-ray dips and spikes (followed by radio flares). We present the time-resolved spectroscopy of these cyclesand show that in all cases the hard X-ray component (the Comptonized emission from a coronal medium) is suppressed in coincidence with a soft X-ray spike that ends the cycle. We interpret these results as evidence that the soft X-ray spike is the trigger of the ejection, and that the ejected medium is the coronal material. In the steady state observation, the X-ray spectrum is indicative of the hard-intermediate state, with the presence of a relatively strong emission at 15 GHz. The X-ray spectra are the sum of a Comptonized component and an extra power law extending to energies >200 keV without any evidence for a cut-off. We observe a possible correlation of the radio flux with that of the power law component, which may indicate that we see direct emission from the jet at hard X-ray energies. We study the energy dependence of a ~4 Hz QPO during the hard-intermediate state observation. The QPO-``spectrum'' is well modeled by a power law with a cut-off at an energy about 11 keV that clearly differs from the relative contribution of the Comptonized component to the overall flux. This may rule out models of global oscillations of the Compton corona.

13 pages, 8 figures (3 color), accepted for publication in ApJ, scheduled for the March 20, 2008, vol676 issue. Paper 1 is the next astro-ph number

References in corpus (2)

• X-ray Properties of Black-Hole Binaries
• Two years of INTEGRAL monitoring of GRS 1915+105 Part 1: multiwavelength coverage with INTEGRAL, RXTE, and the Ryle radio Telescope

Cited by in corpus (10)

• Two years of INTEGRAL monitoring of GRS 1915+105 Part 1: multiwavelength coverage with INTEGRAL, RXTE, and the Ryle radio Telescope
• A unified accretion-ejection paradigm for black hole X-ray binaries. IV. Replication of the 2010--2011 activity cycle of GX 339-4
• The INTEGRAL view on Black Hole X-ray Binaries
• Chasing the break: Tracing the full evolution of a black hole X-ray binary jet with multi-wavelength spectral modeling
• The early phase of a H1743-322 outburst observed by INTEGRAL, RXTE, Swift, and XMM/Newton
• INTEGRAL and XMM-Newton Spectroscopy of GX 339-4 During Hard/Soft Intermediate and High/Soft States in the 2007 Outburst
• INTEGRAL discovery of a high-energy tail in the microquasar Cygnus X-3
• Accretion Flow Properties of GRS 1915+105 During Its $\theta$ Class Using AstroSat Data
• INTEGRAL/IBIS polarization detection in the hard and soft intermediate states of Swift J1727.8-1613
• Searching for quantum-gravity footprint around stellar-mass black holes