Stochastic variability in X-ray emission from the black hole binary GRS 1915+105

TL;DR

This study uses flicker-noise spectroscopy to analyze stochastic variability in X-ray emissions from GRS 1915+105, identifying four distinct modes of variability related to accretion disk processes.

Contribution

It introduces a novel application of flicker-noise spectroscopy to classify variability modes in black hole X-ray emissions, linking them to accretion disk physics.

Findings

Identified four stochastic variability modes: RN, 1F, 1S, 2S.

Found variability modes are consistent across soft and hard energy bands.

Provided parameter estimates for each observation's variability characteristics.

Abstract

We examine stochastic variability in the dynamics of X-ray emission from the black hole system GRS 1915+105, a strongly variable microquasar commonly used for studying relativistic jets and the physics of black hole accretion. The analysis of sample observations for 13 different states in both soft (low) and hard (high) energy bands is performed by flicker-noise spectroscopy (FNS), a phenomenological time series analysis method operating on structure functions and power spectrum estimates. We find the values of FNS parameters, including the Hurst exponent, flicker-noise parameter, and characteristic time scales, for each observation based on multiple 2,500-second continuous data segments. We identify four modes of stochastic variability driven by dissipative processes that may be related to viscosity fluctuations in the accretion disk around the black hole: random (RN), power-law (1F), one-scale (1S), and two-scale (2S). The variability modes are generally the same in soft and hard energy bands of the same observation. We discuss the potential for future FNS studies of accreting black holes.