The photon-index - time-lag correlation in black-hole X-ray binaries

Abstract

We have performed a timing and spectral analysis of a set of black-hole binaries to study the correlation between the photon index and the time lag of the hard photons with respect to the soft ones. We provide further evidence that the timing and spectral properties in black-hole X-ray binaries are coupled. In particular, we find that the average time lag increases as the X-ray emission becomes softer. Although a correlation between the hardness of the X-ray spectrum and the time (or phase) lag has been reported in the past for a handful of systems, our study confirms that this correlated behaviour is a global property of black-hole X-ray binaries. We also demonstrate that the photon-index - time-lag correlation can be explained as a result of inverse Comptonization in a jet.

10 pages, 7 figures, accepted for publications in MNRAS

References in corpus (10)

• The hard X-ray spectral evolution in X-ray binaries and its application to constrain the black hole mass of ultraluminous X-ray sources
• Chandra X-ray spectroscopy of the focused wind in the Cygnus X-1 system. I. The non-dip spectrum in the low/hard state
• A jet model for Galactic black-hole X-ray sources: Some constraining correlations
• Linking Jet Emission, X-ray States and Hard X-ray Tails in the Neutron Star X-ray Binary GX 17+2
• X-ray Polarization in Relativistic Jets
• Accretion and ejection in black-hole X-ray transients
• Effects of Compton Cooling on Outflow in a Two Component Accretion Flow around a Black Hole: Results of a Coupled Monte Carlo-TVD Simulation
• The evolution of the X-ray phase lags during the outbursts of the black hole candidate GX 339-4
• Spectral and Timing Properties of the Black Hole X-ray Binary H 1743-322 in the Low/hard State Studied with Suzaku
• Are spectral and timing correlations similar in different spectral states in black hole X-ray binaries?

Cited by in corpus (12)

• The NICER "Reverberation Machine": A Systematic Study of Time Lags in Black Hole X-Ray Binaries
• Time lags of the type-B QPO in MAXI J1348-630
• The evolution of the broadband temporal features observed in the black-hole transient MAXI J1820+070 with Insight-HXMT
• A quantitative explanation of the type-B QPOs in GX 339-4
• Illumination of the accretion disk in black hole binaries: An extended jet as the primary source of hard X-rays
• Inclination effects on the X-ray emission of Galactic black-hole binaries
• Time-domain variability properties of XTE J1650-500 during its 2001 outburst: Evidence of disc-jet connection
• Evolution of the truncated disc and inner hot-flow of GX 339-4
• The spectral-timing analysis of Cygnus X-1 with Insight-HXMT
• A quantitative explanation of the radio--X-ray correlation in black-hole X-ray binaries
• The role of outflows in black-hole X-ray binaries
• Inclination Dependence of The Time-Lag -- Photon-Index Correlation in BHXRBs and its Explanation with a Simple Jet Model