A model-independent analysis of the variability of GRS 1915+105

TL;DR

This study classifies the variability of GRS 1915+105 into three main states based on X-ray observations, revealing rapid transitions and patterns that connect to black hole accretion models.

Contribution

It provides a model-independent classification of GRS 1915+105's variability into three states and analyzes their transition patterns, linking observations to accretion disk theories.

Findings

Identified three basic states of GRS 1915+105.

Observed rapid state transitions between these states.

Linked variability patterns to accretion disk properties.

Abstract

We analyzed 163 observations of the microquasar GRS 1915+105 made with the Rossi X-ray Timing Explorer (RXTE) in the period 1996-1997. For each observation, we produced light curves and color-color diagrams. We classified the observations in 12 separate classes, based on their count rate and color characteristics. From the analysis of these classes, we reduced the variability of the source to transitions between three basic states: a hard state corresponding to the non-observability of the innermost parts of the accretion disk, and two softer states with a fully observable disk. These two soft states represent different temperatures of the accretion disk, related to different local values of the accretion rate. The transitions between these states can be extremely fast. The source moves between these three states following certain patterns and avoiding others, giving rise to a relatively large but limited number of variability classes. These results are the first step towards a linking of the properties of this exceptional source with standard black-hole systems and with accretion disk models.